Electrostimulation system, and electrostimulation electrode assembly and biological implantable electrode therefore

An electrostimulation system includes a connector connected to an electrostimulation device, a conducting wire pair electrically connected to the connector, an electrical stimulation lead having a sheathing body configured to insulate the conducting wire pair and installed to be inserted into the vein, an electrical stimulus block portion installed at a leading end side of the electrical stimulation lead and having an electrode portion electrically connected to the conducting wire pair and a fixing block configured to bias the electrode portion to the inner wall of the vein, and a rotary member having an engaging groove detachably engaged with the electrical stimulus block portion and configured to rotate the electrical stimulus block portion disposed in the vein about a central axis of the vein disposed in the vein via the engaging groove.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electrostimulation system, and an electrostimulation electrode assembly and a biological implantable electrode therefor. In particular, the present invention relates to an electrostimulation system which applies electrical stimulus to the nervous tissue, an electrostimulation electrode assembly which applies electrical stimulus to the nervous tissue, and a biological implantable electrode which is connected to an electrical stimulus generation device placed in a biological body to apply electrical stimulus to the biological tissue, such as muscles, nerves, or heart, which requires electrical stimulus.

2. Description of Related Art

In the related art, a stimulus generation device is known which applies electrical stimulus for treatment to the nervous tissue or the biological tissue (linear tissue), such as muscles. Examples of the stimulus generation device include a nervous stimulation device, a pain relief device, an epilepsy treatment device, a muscle stimulation device, and the like.

In the stimulus generation device, a conducting wire which transmits electrical stimulus is implanted in the biological body for use so as to bring the conducting wire into close contact with a stimulation target in the biological body.

In general, the conducting wire has at least one electrode portion which applies electrical stimulus to the biological tissue or detects electrical excitation in the biological tissue, an electrical connector which is used for electrical connection to the stimulus generation device, and a lead body which is provided between the electrode portion and the stimulus generation device and transmits electrical stimulus.

For example, Japanese Unexamined Patent Application, First Publication No. 2004-173790 describes an implanted heart treatment device which stimulates the heart when the heart produces bradycardia to increase the heart rate, stimulates the vagus nerve when the heart produces tachycardia or fibrillation to decrease the heart rate. In the heart treatment device, a heart stimulation electrode is arranged inside the myocardium or the atrium, and a nerve stimulation electrode is arranged to be wound around the vagus nerve in the cervical region.

Japanese Unexamined Patent Application, First Publication No. 2008-67978 describes a biological implantable electrode lead which includes an electrode support having at least one arm portion, in which an electrode is formed, the arm portion being loaded to be wound around the biological tissue, such as the cervical vagus nerve.

Heretofore, a device, such as a heart pacemaker, an implantable defibrillation device, a nervous stimulation device, or a deep brain stimulation device, is known which applies electrical stimulus for treatment to the biological tissue, which requires stimulation. The device includes an electrical stimulus generation device which has an internal power supply and an electrical circuit necessary for electrostimulation, an electrode which is loaded in the biological tissue, which requires stimulation, to apply electrical stimulus to the biological tissue, and a conducting wire which transmits electrical information from the stimulus generation device to the electrode.

Of these, the biological implantable electrode placed in the body includes at least one electrode which applies electrical stimulus to the biological tissue, such as the heart, nervous tissue, or muscles, or detects electrical excitation in the biological tissue; a conducting wire sheathing body which has an electrical conductor and a biocompatible insulating sheath connected to the electrode; a connector which electrically connects various electrical stimulus generation devices, such as a heart pacemaker, an implanted defibrillation device, a nervous stimulation device, and a deep brain simulation device, to the conducting wire sheathing body; and the like.

As the biological implantable electrode of the related art, electrodes are known which are described in Japanese Unexamined Patent Application, First Publication Nos. 2008-67978 and 2005-58456. Japanese Unexamined Patent Application, First Publication No. 2008-67978 describes an electrode assembly for nervous stimulation which is implantable into the biological body. In the electrode assembly, an electrode at the tip of a conducting wire sheathing body has an arm portion, and the arm portion is loaded to be wound around the nerve. In the biological implantable electrode described in Japanese Unexamined Patent Application, First Publication No. 2005-58456, a lubricating coated layer is provided in a portion of the surface of an insulating sheath.

SUMMARY OF THE INVENTION

A first aspect of the present invention provides an electrostimulation system. The electrostimulation system includes a sheathed conducting wire member which has a terminal portion to be connected to an electrostimulation device, a conducting wire pair electrically connected to the terminal portion, and a sheathing body insulating the conducting wire pair, and is provided to pass through a vein, an electrostimulation block which is provided on the leading end side of the sheathed conducting wire member, and has an electrode pair electrically connected to the conducting wire pair and an electrode urging member urging the electrode pair toward the inner wall of the vein, and a rotary member which has an engagement portion detachably engaged with the electrostimulation block and rotates the electrostimulation block arranged inside the vein around the center line of the vein through the engagement portion.

According to a second aspect of the present invention, in the electrostimulation system, the electrostimulation block may have a convex portion protruding outside the outer circumference of the sheathed conducting wire member, and the rotary member may be formed in a tubular shape through which the sheathed conducting wire member passes and may have a groove portion provided at the leading end thereof to be engageable with the convex portion in a circumferential direction of rotation.

In the electrostimulation system, the electrostimulation block may have a groove portion formed inside the outer circumference of the sheathed conducting wire member, and the rotary member may be formed in a shaft shape or tubular shape which is passable through the sheathed conducting wire member and may have a convex portion provided to be engageable with the groove portion in a circumferential direction of rotation.

According to a third aspect of the present invention, in the electrostimulation system, the sheathed conducting wire member and the electrostimulation block may have a hollow structure in which hollow portions communicate with each other, a pacing lead which is placed inside a heart may be put in the hollow portions, and the sheathed conducting wire member and the electrostimulation block may be provided rotatably at least in a circumferential direction with respect to the outer circumferential surface of the pacing lead.

The electrode urging member may include an elastic member which has an arc portion having a diameter greater than the inner diameter of the vein in a natural state.

The elastic member may be constituted by a superelastic wire having shape reversibility.

According to a fourth aspect of the present invention, the electrode urging member may be constituted by a cylindrical balloon whose outer diameter is enlargeable and reducible through fluid pressure.

A fifth aspect of the present invention provides an electrostimulation electrode assembly. The electrostimulation electrode assembly includes an electrode which is inserted into a vein and applies electrical stimulus through the inner wall of the vein, an insulating support which supports the electrode in a state where a portion of the electrode is exposed to the surface as an exposed electrode surface, a conducting wire member which is electrically connected to the electrode in the support and extends outside the support, a sheathing member which has a linear shape to pass through the vein and one end portion of which is connected to the support, ensuring that the conducting wire member extending from the support passes therethrough in an insulation state and guided to the other end portion thereof, a terminal portion which is electrically connected to the conducting wire member guided to the other end portion of the sheathing member and provided to be connectable to a stimulus generation device generating electrical stimulus, and an electrode urging member which is connected to the support and urges the electrode exposed from the support toward the inner wall of the vein.

The support may be provided to have a shape so as to cover the entire electrode when viewed from the rear side of the exposed electrode surface.

The support may be provided so as to extend from the one end portion of the sheathing member along the axial direction of the sheathing member, and the electrode urging member may be connected to the support at a position with the exposed electrode surface sandwiched therebetween in the extension direction of the support.

The electrode urging member may include an elastic body which is fixed to the lateral surface of the support at a position with the exposed electrode surface sandwiched therebetween when viewed from the extension direction of the support, extends to both lateral sides of the support in an arc shape such that a direction in which the exposed electrode surface is formed is made convex when viewed from the extension direction of the support, and has a curved portion being curvable along the circumferential direction of the inner wall of the vein.

The elastic body may be constituted by a plurality of linear curved bodies which are arranged to be separated in the extension direction of the support, and a linear leading end connection portion may be provided to connect the leading ends of the plurality of linear curved bodies in the extension direction of the support.

The leading end connection portion may be bent so as to protrude outwardly in the radial direction of curvature from a curved surface in which the plurality of curved bodies are arrayed.

The curved portion may have a U-shaped bent shape in an intermediate portion thereof.

The electrode urging member may have an elastic body which is fixed to the lateral surface of the sheathing member at a position in the one end portion of the sheathing member with the exposed electrode surface sandwiched therebetween when viewed from the axial direction of the sheathing member, extends to both lateral sides of the sheathing member in an arc shape such that a direction in which the exposed electrode surface is formed is made convex when viewed from the axial direction of the sheathing member, and has a curved portion being curvable along the circumferential direction of the inner wall of the vein. The support may be provided on the electrode urging member.

According to a sixth aspect of the present invention, the elastic body may be made of a conductive material and may double as the conducting wire member in the support.

A seventh aspect of the present invention provides a biological implantable electrode. The biological implantable electrode includes an electrode portion which applies electrical stimulus to a biological tissue, an elongated conductive wire sheathing body which connects the electrode portion and the electrical stimulus generation device, and an electrode support which supports the electrode portion in the biological body. The electrode support is reversibly deformable to a first shape suitable for supporting the electrode portion in the biological body and a second shape suitable for introducing and removing the electrode portion with respect to the biological body.

According to an eighth aspect of the present invention, the biological implantable electrode may further include a deformation mechanism which deforms the electrode support to the second shape. The electrode support may be maintained in the first shape in a natural state where external force is not applied.

The deformation mechanism may have a tubular member through which the conducting wire sheathing body passes, and the electrode support may be accommodated inside the tubular member to be deformed to the second shape.

A ninth aspect of the present invention provides a method of adjusting an electrostimulation system. The method includes an electrostimulation block insertion step of passing an electrostimulation block formed at the leading end of a sheathed conducting wire member through a vein and urges an electrode the pair of electrostimulation block toward the inner wall of the vein, an electrode alignment step of rotating and adjusting the electrostimulation block on the basis of the behavior of an electrostimulation pulse of a nervous tissue around the vein, and an electrostimulation step of applying an electrostimulation pulse to the nervous tissue around the vein.

The method according to the ninth aspect of the present invention may further include an electrostimulation block ejection step of ejecting the electrostimulation block from the vein after a desired electrostimulation pulse is applied.

A tenth aspect of the present invention provides a method of deforming a biological implantable electrode. The method includes a second shape deformation step of deforming an electrode support so as to pass through a vein, a first shape deformation step of deforming the electrode support for support in the vein, and a second shape re-deformation step of deforming the electrode support to the second shape again so as to be removed from the vein.

An eleventh aspect of the present invention provides a method of placing an electrostimulation system. The method includes an electrode unit insertion step of inserting an electrode unit into a vein, an electrode unit disposition step of disposing the electrode unit in a superior vena cava in the vicinity of a vagus nerve, an electrode unit biasing step of biasing a stimulation electrode included in the electrode unit in a direction of the vagus nerve, and an electrical stimulation step of applying electrical stimulus energy to the vagus nerve.

A twelfth of the present invention provides a method of placing the electrostimulation system. The method further includes a thrombus formation prevention step after the electrode unit disposition step.

The thrombus formation prevention step may be an anticoagulant agent discharge step of discharging an anticoagulant agent from a liquid feed tube opening formed in the electrode unit.

A thirteenth aspect of the present invention provides a method of placing the electrostimulation system. The method further includes an electrode ejection unit ejection step of ejecting an electrode unit from a vein after application of desired electrical stimulus energy.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In all the drawings, even when embodiments are different, the same or similar members are represented by the same reference numerals, and common description will be omitted.

An electrostimulation system according to a first embodiment of the present invention will be described.

FIG. 1Ais a schematic sectional view showing a state when an electrostimulation system according to a first embodiment of the present invention is loaded in a superior vena cava.FIG. 1Bis a schematic perspective view of an A portion ofFIG. 1Aon a magnified scale.FIG. 2is a sectional view taken along the line B-B ofFIG. 1B.FIG. 3Ais a schematic front view of a sheathed conducting wire member and an electrostimulation block which are used in the electrostimulation system according to the first embodiment of the present invention.FIGS. 3B and 3Care respectively a diagram when viewed from a direction indicated by an arrow C of3A and a sectional view taken along the line D-D ofFIG. 3A.FIG. 4is a partial sectional view taken along the axial direction of the sheathed conducting wire member and the electrostimulation block which are used in the electrostimulation system according to the first embodiment of the present invention.FIG. 5Ais a schematic front view of a rotary member which is used in the electrostimulation system according to the first embodiment of the present invention.FIG. 5Bis an enlarged view of an E portion ofFIG. 5A.FIG. 5Cis a diagram when viewed from a direction indicated by an arrow F ofFIG. 5B.

The drawings are schematic views, thus the shape or dimension is magnified (the same is applied to the following description).

As shown inFIGS. 1A and 1B, an electrostimulation system101of this embodiment includes an electrostimulation lead102(sheathed conducting wire member), an electrostimulation block portion103(electrostimulation block), and a rotary member107.

The electrostimulation system101includes the electrostimulation lead102which is connected to an electrostimulation device1200implanted in or provided outside a biological body, and the electrostimulation block portion103which is provided at the leading end of the electrostimulation lead102. For example, the electrostimulation system101is configured such that the electrostimulation block portion103is inserted into a vein, such as a superior vena cava V1, along with the electrostimulation lead102, and electrically stimulates a nervous tissue, for example, a vagus nerve VN, outside the vein from the electrostimulation block portion103.

In recent years, in the field of a treatment of cardiac failure, it becomes clear that, when chronic cardiac failure is exacerbated, the prognosis becomes worse. It is known that a nervous stimulation device is used to apply electronic intervention directly to an automatic nerve, thereby correcting circulation dysregulation.

The electrostimulation system101of the embodiment can be particularly appropriate for a treatment in which electrical stimulus is applied to a nervous tissue near a heart H.

Hereinafter, as shown inFIGS. 1A,1B, and2, an example will be described where the electrostimulation block portion103of the electrostimulation system101is inserted from the superior vena cava V1and placed in the inner wall portion of a vein near the vagus nerve VN, and applies electrical stimulus to the vagus nerve VN.

Although the sectional shape of a vein inner wall Vsof the superior vena cava V1is different from a geometrically true circle, for convenience, description will be provided assuming a circular shape because the vein inner wall Vsis maintained in a shape capable of being approximated to a circular shape due to a blood pressure. That is, hereinafter, when the vein inner wall Vsis regarded as a circle, this indicates an approximate circle, and an inner diameter indicates the diameter of the approximate circle.

Hereinafter, in expressing the positional relationship of a member to be inserted into a vein along the axial direction, if there is no room for misunderstanding, the leading end side in the insertion direction may be simply referred to as the leading end side, and the opposite side to the leading end side may be referred to as the base end side. The terms leading end, leading end portion, and the like may be used to mean the same positional relationship.

The electrostimulation system101can apply electrical stimulus to any nervous tissue insofar as the nervous tissue is near the vein, and is not limited to the purpose for an electrostimulation treatment of the vagus nerve VN.

The electrostimulation device1200which is connected to the electrostimulation system101uses a battery as a power source and generates an electrostimulation pulse set in advance. In particular, when the electrostimulation device1200is provided outside the body, a liquid crystal screen for set value display may be provided. Wireless communication with an exclusive-use controller (not shown) may be performed to remotely change the setting of the electrostimulation conditions or acquire the operation history.

The electrostimulation conditions of the electrostimulation device1200include the magnitude of the electrostimulation pulse voltage, frequency, pulse width, stimulation end time, stimulation start time, stimulation duration time, electrostimulation stoppage, and the like.

The schematic configuration of the electrostimulation lead102is as shown inFIGS. 3A,3B,3C, and4. That is, the electrostimulation lead102includes a connector104(terminal portion), a sheathing tube102d, a pair of conducting wires102aand102b, and a sheathing member102c(sheathing body). As a whole, the electrostimulation lead102is an elongated linear body.

The connector104is a terminal portion which is connected to a connection terminal1200a(seeFIG. 1A) provided on the surface of the electrostimulation device1200. The connector104is provided on the base end side in the insertion direction of the electrostimulation lead102into the vein.

As the connector type of the connector104, an appropriate connector type according to the shape of the connection terminal1200aof the electrostimulation device1200may be used.

In this embodiment, an IS1 connector is used which is used when the electrostimulation device1200is provided inside the body. That is, the connector104includes a connector pin104afor a negative electrode and a connector pin104bfor a positive electrode, and a pair of rubber rings104c. The rubber rings104cinsulate the connector pin104afor a negative electrode and a connector pin104bfor a positive electrode and also remain watertight at the time of connection to the connection terminal1200b.

The connector pin104afor a negative electrode and the connector pin104bfor a positive electrode are both made of stainless steel. The rubber rings104care formed of silicone rubber having biocompatibility.

As another connector type of the connector104, a waterproof connector may be used which is used when the electrostimulation device1200is provided outside the body.

The conducting wire102ais a linear or coil-like electrical conductor which electrically connects the connector pin104afor a negative electrode and a negative electrode105a(described below) of the electrostimulation block portion103. The shape or material of the conducting wire102ais not particularly limited insofar as the conducting wire102ais resistant to bending in the vein into which the electrostimulation lead102is inserted. In this embodiment, for example, a twisted wire made of nickel-cobalt alloy is used.

The conducing wire102bis a linear or coil-like electrical conductor which electrically connects the connector pin104bfor a positive electrode and a positive electrode105b(described below) of the electrostimulation block portion103. With regard to the conducting wire102b, the same shape and material as the conducting wire102amay be used. In this embodiment, for example, a twisted wire made of nickel-cobalt alloy is used.

As shown inFIG. 4, the conducting wires102aand102bwhich are respectively connected to the connector pin104afor a negative electrode and the connector pin104bfor a positive electrode pass through the sheathing tube102dwhich sheaths the conducting wires102aand102bin a state of being insulated from each other, are guided to the base end portion of the sheathing member102cto which the sheathing tube102dis connected, and pass through the sheathing member102c.

As the material of the sheathing tube102d, for example, polyurethane resin may be used.

As shown inFIGS. 3A and 4, the sheathing member102cis a solid linear member through which the conducting wires102aand102bare passed from the base end side, to which the sheathing tube102dis connected, and is wired toward the negative electrode105aand the positive electrode105bwhich sheathes the conducting wires102aand102bso as not to come into contact with each other and not to be exposed to the outside.

The outer shape in the sectional shape of the sheathing member102cis formed by a smooth curved surface which comes into smooth contact with the inner wall of the vein, such as the superior vena cava V1, and is rotatable in the circumferential direction. For example, a circular shape, an elliptical shape, an oval shape, or an approximate shape may be used.

In this embodiment, the sectional shape of the sheathing member102cis a circular shape having an outer diameter sufficiently smaller than the inner wall of the superior vena cava V1so as not to interfere with the blood flow at the time of insertion into the superior vena cava V1. As described below, the sheathing member102chas an outer diameter so as to pass through the rotary member107which has an outer diameter so as to pass through the superior vena cava V1. For example, it is preferable that the diameter of the sheathing member102cis set in a range of φ1 mm to φ2.5 mm. In this embodiment, the diameter of the sheathing member102cis φ2 mm.

The sheathing member102cis made of a material having electrical insulation, flexibility, and biocompatibility in the vein. As the material of the sheathing member102c, in this embodiment, a polyurethane resin is used.

The outer surface of the sheathing member102cmay be subjected to thrombus prevention coating.

The electrostimulation block portion103includes a columnar support103awhich is provided coaxially with the sheathing member102cconnected to the leading end side of the sheathing member102c, an electrode portion105which is supported by the support103a, and fixing hooks106R and106L (electrode urging member) which are attached to the outer circumferential surface of the support103ato urge the electrode portion105toward the vein inner wall Vs, such as the superior vena cava V1.

The support103ais provided on the leading end side of the sheathing member102c, and supports the electrode portion105and the fixing hooks106R and106L in the lateral surface. The support103ahas passes therethrough the conducting wires102aand102bextending from the sheathing member102cin a state of being insulated from each other and guides the conducting wires102aand102bto the electrode portion105.

In this embodiment, the support103ahas a columnar outer shape having the same diameter as the sheathing member102c, and is molded as a single body with the sheathing member102cby using the same insulating material as the sheathing member102c.

The electrode portion105is constituted by an electrode the pair of negative electrode105awhich is electrically connected to the conducting wire102ainside the support103aand the positive electrode105bwhich is electrically connected to the conducting wire102binside the support103a.

As shown inFIGS. 3A and 3B, the negative electrode105aand the positive electrode105bare such that a rectangular electrode surface in side view is exposed from the lateral surface of the support103a. With regard to the arrangement position on the lateral surface of the support103a, the negative electrode105aand the positive electrode105bare arranged in a column with a space in the axial direction of the support103a. In this embodiment, the negative electrode105aand the positive electrode105bare arranged in that order from the leading end side of the support103a. The length of each electrode surface of the negative electrode105aand the positive electrode105bis, for example, 2 mm, and the gap (separation interval) in the axial direction between the negative electrode105aand positive electrode105bis set to, for example, 5 mm.

As shown inFIG. 3C, the shape of the negative electrode105ain the cross-section perpendicular to a central axis O3of the support103ais an arch shape in which the exposed electrode surface substantially follows the outer shape of the support103aor slightly protrudes. That is, the exposed electrode surface of the negative electrode105ais constituted by a partial cylindrical surface.

The internal shape of the support103ais not particularly limited insofar as the support can be fastened to the support103a. For example, inFIG. 3C, the internal shape is substantially a flat plate shape, and the sectional shape including the electrode surface is a D shape. The internal shape may be a V shape which is made convex toward the central axis O3of the support103a, a U shape, or the like. A reverse T shape or an arrow shape protruding downward in the drawing may be provided or an external screw shape or a multi-ring shape may be provided in the outer circumferential portion such that the withdrawal resistance outwardly in the radial direction with respect to the support103aincreases.

The positive electrode105bhas the same shape as the negative electrode105a.

The length (the exposed length in the circumferential direction) of an arc in each electrode surface of the negative electrode105aand the positive electrode105bis set such that electrical stimulus can be efficiently applied to the nervous tissue outward in the radial direction through the vein inner wall in close contact therewith when each electrode is pressed against the superior vena cava V1.

While depending on the ratio between the radius of curvature of the vein inner wall Vsand the radius of the arc of the electrode surface, for example, if the center angle (hereinafter, referred to as an electrode exposure angle) of the arc of the electrode surface is greater than 180°, electricity is likely to leak to another peripheral tissue. For this reason, a semicircular shape or a minor arcuate shape is preferably used such that the electrode surface can be directed outward in the radial direction of the vein.

In this embodiment, because the vagus nerve VN around the superior vena cava V1is stimulated, there is possibility that electricity may leak and stimulate a nearby phrenic nerve or the like.

In the case of a major arc or a near-circular minor arc, the negative electrode105aand the positive electrode105beasily come into contact with blood. For this reason, electrical energy flows through blood, and electrical energy which is applied to a vascular tissue facing the vagus nerve VN decreases, making it difficult to stimulate the vagus nerve VN.

For this reason, in this embodiment, it is preferable that the electrode exposure angle is equal to or smaller than 120°.

If the electrode exposure angle is excessively small, the range in which electrical stimulus is applied in the circumferential direction is excessively narrowed, so a high voltage should be applied for electrostimulation.

For this reason, it is preferable that the electrode exposure angle is equal to or greater than 30°.

In this embodiment, for example, when the outer radius of the support103ais 1 mm, the electrode surface of the negative electrode105ahas a radius of 1 mm and an electrode exposure angle of 90°.

In this embodiment, each of the fixing hooks106R and106L is formed by bending a linear elastic member in a U shape (angulated U shape) and has arcuate arm portions106aand106cand a hook leading end portion106b.

As shown inFIGS. 3B and 3C, the fixing hooks106R and106L are formed and arranged so as to be plane-symmetric to the plane including the center line in the axial direction, which is common to the electrode surfaces of the negative electrode105aand the positive electrode105barranged in the axial direction of the support103a, and the central axis O3of the support103a. The fixing hook106R is located on the right when viewed from the base end side of the support103ato the leading end side in a state where the electrode surface of the electrode portion105turns upward, and the fixing hook106L is located on the left side in the same manner.

As the material of the fixing hooks106R and106L, an appropriate elastic material may be used which can press the vein inner wall Vsby elastic restoring force.

More preferably, a shape-restorable elastic material is used which has flexibility so as to be a little foldable when inserted into the vein and can urge the inner wall of the vein. Examples of such a material include a superelastic alloy which has shape-reversibility so as to be easily elastically deformed by external force and to return to the state before deformation if external force is removed, for example, a nickel-titanium-based alloy. In this embodiment, as an example, a member is used which is formed by molding a superelastic wire having a diameter φ0.3 mm made of a nickel-titanium-based alloy in a U shape.

Though not particularly shown, the fixing hooks106R and106L are configured such that the outer circumferential surface of the superelastic wire is covered with polyurethane tube coating or fluorine resin-based coating. For this reason, the superelastic wire does not come into direct contact with blood in the vein or the vein inner wall Vs. Since polyurethane or fluorine resin has small frictional resistance against the vein inner wall Vsthe polyurethane tube coating or fluorine resin-based coating allow smooth sliding along the vein inner wall Vs.

Similarly to the sheathing member102c, the tube is preferably subjected to thrombus prevention coating.

Hereinafter, unless specially noted, description will be provided assuming that the shapes of the arcuate arm portions106aand106cand the hook leading end portion106bwhich are common to the fixing hooks106R and106L are in the natural state where no external force is applied.

The arcuate arm portion106ais configured such that a fixed shaft end106d(convex portion) protrudes from the leading end side compared to the negative electrode105ain the lateral surface of the support103a. The arcuate arm portion106ais constituted by a linear body which protrudes obliquely from the fixed shaft end106doutwardly in the radial direction is curved toward the opposite side to the electrode surface of the negative electrode105aso as to substantially have an arc shape when viewed from the axial direction.

The position in the circumferential direction of the fixed shaft end106dis set to a position distant from the end portion in the circumferential direction of the negative electrode105aoutwardly in the circumferential direction. For this reason, as shown inFIG. 3C, when the electrode surface of the negative electrode105aturns upward, the fixed shaft end106dprotrudes from the lower lateral surface compared to the electrode surface of the negative electrode105a.

As indicated by a two-dot-chain line ofFIG. 2, the radius of curvature of the arc shape of the arcuate arm portion106ais set to be greater than the radius of the vein inner wall Vsof the superior vena cava V1.

The length of the arcuate arm portion106ais equal to or greater than ¼ of the circumferential length of the vein inner wall Vsat a position in the superior vena cava V1where the electrostimulation block portion103is provided.

The arcuate arm portion106cis configured such that a fixed shaft end106eprotrudes from the base end side compared to the positive electrode105bin the lateral surface of the support103a. The arcuate arm portion106cis constituted by a linear body which protrudes obliquely from the fixed shaft end106eoutward in the radial direction in the same direction as the arcuate arm portion106aand is curved toward the opposite side to the electrode surface of the positive electrode105bso as to substantially have an arc shape when viewed from the axial direction.

The position in the circumferential direction of the fixed shaft end106eand the curved shaped of the arcuate arm portion106care set so as to overlap the arcuate arm portion106awhen viewed from the axial direction of the support103a.

For this reason, similarly to the fixed shaft end106d, when the electrode surface of the positive electrode105bturn upward, the position in the circumferential direction of the fixed shaft end106eis set such that the fixed shaft end106eprotrudes from the lower lateral surface compared to the electrode surface of the positive electrode105b.FIG. 2shows a state where the positional relationship is rotated left by 90°.

As shown inFIGS. 3A and 3B, the hook leading end portion106bis a linear body which extends in the axial direction of the support103awhile connecting the leading ends in the protrusion direction of the arcuate arm portions106aand106c. Both end portions of the hook leading end portion106band the leading ends in the protrusion direction of the arcuate arm portions106aand106cform corner portions having an R shape. Thus, the fixing hooks106R and106L can come into smooth contact with and slide along the vein inner wall Vs.

The fixing hooks106R and106L are respectively constituted by the arcuate arm portions106aand106cand the hook leading end portion106bso as to be arrayed on the cylindrical surface having a diameter greater than the vein inner wall Vsextending laterally from the lateral surface of the support103aand to have a U shape with the fixed shaft ends106dand106eas an opening end.

Thus, when the electrostimulation block portion103is inserted into the superior vena cava V1, as shown inFIG. 2, the fixing hooks106R and106L can be elastically deformed along the vein inner wall Vsand can urge the vein inner wall Vsoutward in the radial direction in accordance with the deformation amount.

In this embodiment, the sheathing member102cand the support103ahave the same outer diameter, such that the fixed shaft end106econstitutes a convex portion which protrudes to a position outside the outer circumference of the sheathing member102c.

As described above, the electrostimulation block portion103is provided on the leading end side of the electrostimulation lead102. The electrostimulation block portion103has the negative electrodes105aand105bwhich are an electrode pair electrically connected to the conducting wires102aand102bas an conducting wire pair, and the fixing hooks106R and106L which urge the electrode pair toward the vein inner wall Vs.

The length of each of the arcuate arm portions106aand106cis equal to or greater than ½ of the circumferential length in the cross-section perpendicular to the central axis OVof the vein inner wall Vssuch that in urging toward the vein inner wall Vs, the fixing hooks106R and106L are deformed in a shape following the arcuate curved shape of the vein inner wall Vs. For this reason, the fixing hooks106R and106L and the support103aconnected to the fixing hooks106R and106L are arranged along the vein inner wall Vs, the flow of blood in the superior vena cava V1is not easily inhibited. As a result, even when the electrostimulation block portion103is placed in the vein, it is possible to suppress the occurrence of thrombus.

As shown inFIG. 1B, the rotary member107has engagement grooves107d(engagement portions) which are detachably engaged with the electrostimulation block portion103, and rotates the electrostimulation block portion103inserted into the superior vena cava V1around the central axis Ovof the superior vena cava V1through the engagement groove107d. In this embodiment, the rotary member107serves as an introducer which is a tubular member for guiding insertion of the electrostimulation block portion103and the electrostimulation lead102into the superior vena cava V1.

The schematic configuration of the rotary member107is as shown inFIGS. 5A,5B, and5C. That is, the rotary member107includes a tubular portion107awhich substantially has a cylindrical tubular shape, a pair of engagement grooves107d(engagement portions) which are provided at the leading end of the tubular portion107a, and an insertion slot portion107bwhich is provided at the base end of the tubular portion107a, into which the electrostimulation block portion103and the electrostimulation lead102will be inserted, and is embedded with a blood leakage prevention valve (not shown).

The outer diameter of the tubular portion107ais smaller than the inner diameter of the superior vena cava V1. In particular, the leading end portion of the tubular portion107ais tapered such that the diameter is reduced toward the leading end side.

The inner diameter of a through hole107cwhich passes through the tubular portion107ais greater than the outer diameter of the sheathing member102cand is set such that the fixing hooks106R and106L of the electrostimulation block portion103can pass therethrough in a folded state. That is, the through hole107chas an inner diameter which is greater than at least a diameter obtained by adding two times the wire diameter of the fixing hooks106R and106L to the outer diameter of the support103a.

In this embodiment, the shape of each engagement groove107dis constituted by a V-shaped cutout which is opened in the circumferential direction in the leading end portion of the tubular portion107awith a decreasing width toward the base end side in the lateral surface of the leading end portion.

The size of the V shape of each engagement groove107dis set such that the opening is greater than the wire diameter of the fixed shaft end106eof each of the fixing hooks106R and106L, and the groove depth is greater than at least half of the wire diameter of the fixed shaft end106e. Thus, the engagement groove107dcan be engaged with the corresponding fixed shaft end106ein the circumferential direction of the tubular portion107a.

In this embodiment, the position in the circumferential direction of each engagement groove107dis set at a position where the circumference is divided unequally. For this reason, a virtual line which connects the center of each engagement groove107dconstitutes a chord which does not pass through a central axis O7in the circumference at the leading end of the tubular portion107a.

Thus, when each engagement groove107dis engaged with the corresponding fixed shaft end106e, as shown inFIG. 2, engagement can be made in a state where the central axis O3of the support103ais decentered toward the electrode portion105with respect to the central axis O7of the through hole107c. In this embodiment, the lateral surface of the support103aon the electrode portion105side is decentered to an extent so as to be inscribed in the through hole107cat the leading end.

When the lateral surface of the support103aon the electrode portion105can be inscribed in the through hole107cat the leading end in accordance with the position where the fixed shaft end106eis provided, the engagement groove107dmay be arranged to face the diameter direction of the through hole107c.

As described above, the rotary member107is formed in a tubular shape through which the electrostimulation lead102passes, and includes the engagement grooves107dwhich are groove portions provided to be engageable with the fixed shaft ends106eas the convex portions of the electrostimulation block portion103in the circumferential direction of rotation.

The rotary member107can be configured by providing a pair of engagement grooves107dat the leading end of an appropriate introducer which is used when a catheter-like member is inserted into the vein. For this reason, the shape of a portion of the rotary member107excluding the engagement grooves107dcan be similar to an appropriate introducer in the related art. That is, an introducer in the related art is of a peel-off type (tearing elimination type) or the like, and this shape type may be used.

For example, as an introducer which can be used as the rotary member107when the engagement grooves107dare provided, Radifocus (Registered Trademark) introducer IIH (Product Name: manufactured by Terumo Medical Products) is an exemplary example.

Next, an operation to apply electrical stimulus to the vagus nerve VN in the electrostimulation system101will be described focusing on a method which places the electrostimulation block portion103in the superior vena cava V1.

FIGS. 6A,6B, and6C are process explanatory views showing an electrostimulation block insertion process in the electrostimulation system according to the first embodiment of the present invention.FIG. 7is a process explanatory view showing an electrode alignment process in the electrostimulation system according to the first embodiment of the present invention.FIGS. 8A and 8Bare operation explanatory views in a cross-section taken along the line G-G ofFIG. 7.

In applying electrical stimulus to the vagus nerve VN by the electrostimulation system101, an electrostimulation block insertion process, an electrode alignment process, and an electrostimulation process are performed sequentially.

The electrostimulation block insertion process is a process in which the electrostimulation block portion103of the electrostimulation system101is inserted into the superior vena cava V1along with the electrostimulation lead102.

In this process, as shown inFIG. 6A, an operator makes an incision on a skin S in the cervical region to form an incision portion CL for inserting the rotary member107into the superior vena cava V1.

Next, as shown inFIG. 6B, the operator inserts the tubular portion107ainto the incision portion CL from the leading end side and moves the leading end of the rotary member107toward the heart H in the superior vena cava V1so as to be placed near the vein portion in the vicinity of the vagus nerve VN, which will be subjected to electrostimulation.

At this time, the blood leakage prevention valve is embedded in the insertion slot portion107bof the rotary member107, such that, during the insertion process, it is possible to reduce blood leakage outside the body and also to realize insertion into the vein in a short time.

Next, the operator inserts the electrostimulation block portion103and the electrostimulation lead102from the insertion slot portion107bin a state where the position of the rotary member107is fixed. At this time, the fixing hooks106R and106L have excellent flexibility, such that, when the electrostimulation block portion103is inserted into the rotary member107, bending deformation occurs in a range of a gap between the through hole107cand the support103aand the through hole107cand the sheathing member102c, and the electrostimulation block portion103is folded. The fixing hooks106R and106L are constituted by a linear member which is bent so as to have an R shape in the corner portion, and do not have a shape to be caught by the inner circumferential surface of the through hole107c. Thus, the fixing hooks106R and106L can smoothly slide in the axial direction in a folded state.

When the operator further inserts the electrostimulation lead102, as shown inFIG. 6C, the electrostimulation block portion103emerges from the leading end of the rotary member107and is moved into the superior vena cava V1.

When the electrostimulation block portion103emerges from the rotary member107, external force from the through hole107cwhich folds the fixing hooks106R and106L does not apply to the fixing hooks106R and106L, such that the fixing hooks106R and106L try to return to the shape in the natural state.

The shape in the natural state of the fixing hooks106R and106L is greater than the inner diameter of the vein inner wall Vsof the superior vena cava V1(see the two-dot-chain line ofFIG. 2). For this reason, the fixing hooks106R and106L come into contact with the vein inner wall Vsand urge the vein inner wall Vsoutward in the radial direction.

In the cross-section perpendicular of the central axis Ovof the vein inner wall Vs, the arcuate arm portions106aand106cof each of the fixing hooks106R and106L have a length equal to or greater than half of the circumferential length of the vein inner wall Vssuch that the electrode portion105in the support103ais reliably urged outward in the radial direction. For this reason, the electrode portion105is urged to the vein inner wall Vs, and each electrode surface comes into close contact with the vein inner wall Vs. Thus, even when the base end of the electrostimulation lead102is rotated, the electrostimulation block portion103is fixed in a state where the position of the electrode portion105in the circumferential direction is not changed.

With the above, the electrostimulation block insertion process ends.

Next, the electrode alignment process is performed. This process is a process in which the electrode portion105is aligned at a position where the vagus nerve VN in the vicinity of the superior vena cava V1can be efficiently stimulated.

First, as shown inFIG. 7, the operator fixes the position of the electrostimulation block portion103to feed the rotary member107toward the electrostimulation block portion103and rotates rotary member107while the leading end of the rotary member107comes into contact with the arcuate arm portions106c, such that the engagement grooves107dare engaged with the fixed shaft ends106eof the fixing hooks106R and106L. Thus, when the rotary member107is rotated, rotational force is transmitted to the electrostimulation block portion103through the fixed shaft ends106e, thereby rotating the position of the electrostimulation block portion103against frictional force between the fixing hooks106R and106L and the vein inner wall Vs. Even during the rotation, urging force is applied from the fixing hooks106R and106L to the vein inner wall Vs. For this reason, the electrostimulation block portion103is rotated while maintaining the state along the circumferential direction in the vein inner wall Vsalong with the electrode portion105.

As shown inFIG. 8A, if the position of the electrode portion105is excessively distant from the vagus nerve VN in the circumferential direction of the vein inner wall Vs, the vagus nerve VN is not electrically stimulated. For this reason, the operator rotates the rotary member107to carry out rotation adjustment of the electrostimulation block portion103such that, as shown inFIG. 8B, the electrode portion105is placed to face the vagus nerve VN in the radial direction with the vein inner wall Vssandwiched therebetween.

Determination on whether or not the electrode portion105is at the facing position may be made, for example, by connecting the connector104of the electrostimulation lead102to the electrostimulation device1200and monitoring the heart rate using an external electrocardiogram while applying electrostimulation pulses. If the electrode portion105goes to the position facing the vagus nerve VN, a decrease in the heart rate is observed. Thus, a position where the heart rate decreases the most may be found.

When the electrode portion105is adjusted with respect to a sympathetic nerve, a position where the heart rate increases may be found.

When the electrode portion105faces the vagus nerve VN, the rotation of the rotary member107stops and the alignment ends. Then, the rotary member107is withdrawn to the base end side to disengage the rotary member107from the electrostimulation block portion103.

When the electrostimulation block portion103is implanted in the body or placed in the body for a long time, similarly to the introducer in the related art, the rotary member107is, for example, torn or the like and removed outside the vein or the body.

With the above, the electrode alignment process ends.

Next, the electrostimulation process is performed. This process is a process in which electrostimulation pulses set in advance are applied from the electrostimulation device1200to the electrode portion105of the electrostimulation block portion103facing the vagus nerve VN through the vein inner wall Vsin the vicinity of the vagus nerve VN to carry out an electrostimulation treatment of the vagus nerve VN.

As described above, according to the electrostimulation system101of this embodiment, the electrostimulation block portion103can be inserted into the vein and the position thereof can be adjusted in the circumferential direction with respect to the vein inner wall Vsby the rotary member107and can urge the electrode portion105to be attached to the vein inner wall Vsby the fixing hooks106R and106L. For this reason, electrical stimulus can be indirectly applied to a nervous tissue in the vicinity of a vein without being in direct contact with the nervous tissue.

The fixing hooks106R and106L are provided, such that each electrode surface of the electrode portion105can be reliably urged to the vein inner wall Vsand electrostimulation energy can be applied to a stimulation target (nerve or the like) outside the vein, into which the electrostimulation block portion103is inserted. At this time, since the electrode exposure angle is set in a range of 30° to 120°, the urged electrode surface comes into close contact with the vein inner wall Vs, such that the electrode surface is not in contact with blood. For this reason, electrostimulation energy is efficiently transmitted to the stimulation target without leaking into blood.

The electrostimulation block portion103can be aligned by the rotary member107so as to accurately face the stimulation target, minimizing the inter-electrode distance with respect to the stimulation target. As a result, electrostimulation can be carried out at a low voltage, and unnecessary stimulation to a portion which will not be stimulated, such as a phrenic nerve or a heart, can be reduced.

The rotary member107of this embodiment is a tubular member into which the electrostimulation block portion103and the electrostimulation lead102are insertable, and serves as an introducer which passes the electrostimulation block portion103and the electrostimulation lead102through the vein. For this reason, even when an introducer or the like is not separately prepared, insertion into the vein or removal from the vein can be easily carried out.

Since the electrostimulation block portion103is insertable into the vein in a state of being folded in the rotary member107, it is possible to insert the electrostimulation block portion103greater than the cross-section of the vein with a load similar to the introducer of the related art. For this reason, for example, there is no case where the flow of blood is inhibited or the vein inner wall is damaged at the time of insertion into the vein.

As described above, according to this embodiment, in the electrostimulation for a linear tissue, such as a nervous tissue, nervous stimulation can be realized without causing surgical invasion to a nervous tissue as a target. The placement of the electrostimulation lead can be realized by a general transvenous approach which is in heavy usage at the time of catheter operation. In this case, electrostimulation is done indirectly, and the placement of the electrostimulation lead can be completed in a short time without regard to damage of a nervous tissue.

Next, first to third modifications of the electrostimulation system of this embodiment will be described.

In these modifications, only the shape of the engagement grooves107dof the rotary member107which is used in the electrostimulation system of the first embodiment is changed.

With regard to the engagement grooves107d, an example has been described where the sides which transmit rotational force for rotating the fixed shaft ends106eare constituted by obliquely intersecting sides in the axial direction. However, the engagement portion of the rotary member is not particularly limited insofar as a cutout is provided to be of a size to accommodate the fixed shaft ends106eand to have sides which intersect in the rotation direction to transmit rotational force. Hereinafter, these modifications will be described focusing on the differences from the first embodiment.

FIGS. 9A to 9Care partial enlarged views showing a main part of a modification (first to third modifications) of the rotary member in the electrostimulation system according to the first embodiment of the present invention in front view.

As shown inFIG. 9A, a rotary member107A of the first modification includes rectangular grooves107e(engagement portions), instead of the engagement grooves107dof the rotary member107of the first embodiment.

The rectangular grooves107eare cutouts which are formed in a rectangular shape in side view to have a groove width greater than the wire diameter of the fixed shaft ends106eand a groove depth greater than half of the wire diameter of the fixed shaft ends106e.

According to this modification, since the groove width is uniform in the axial direction, even in a state where the fixed shaft ends106edo not reach the groove bottom, rotational force can be transmitted to the electrostimulation block portion103. For this reason, even when the position of the rotary member107A is shifted in the axial direction during the rotation, the rotary member107A can be continuously rotated. The rotation can be made without urging the fixed shaft ends106ein the axial direction of the support103a, reducing a load on the operator and reducing the possibility that the electrostimulation block portion103is moved in the axial direction of the vein inner wall Vs.

As shown inFIG. 9B, a rotary member107E of the second modification includes semicircular grooves107f(engagement portions), instead of the engagement grooves107dof the rotary member107of the first embodiment.

The semicircular grooves107fare semicircular cutouts which have a diameter slightly greater than the wire diameter of the fixed shaft ends106eso as to be detachably engageable with the fixed shaft ends106e.

According to this modification, since the semicircular grooves are detachably engageable with the fixed shaft ends106e, transmission efficiency of rotational force to the fixed shaft ends106eincreases, and thus efficient working can be done.

In this modification, the cutouts may be modified to cutouts which are formed in a U shape in side view with a parallel groove slightly greater than the wire diameter of the fixed shaft ends106e.

As shown inFIG. 9C, a rotary member107C of the third modification includes T-shaped grooves107j(engagement portions), instead of the engagement grooves107dof the rotary member107of the first embodiment.

The T-shaped grooves107jare cutouts which are formed in a T shape in side view, and have an axial slit107gon a parallel groove formed on the leading end side to extend in the axial direction and a circumferential groove107hprovided to be bent from the base end side of the axial slit107gto both outer sides in the circumferential direction.

The opening width of the axial slit107gand the width in the axial direction of the circumferential groove107hare set to be greater than the wire diameter of the fixed shaft ends106e.

According to this modification, each fixed shaft end106eis inserted on the leading end side within the range of the axial slit107gto collide against the distal side, and the rotary member107C is rotated, such that the fixed shaft end106eis moved into the circumferential groove107hextending to the opposite side to the rotation direction. Thus, during the rotation, in a state where the positions in the axial direction of the fixed shaft end106eis regulated within the range of the groove width in the axial direction of the circumferential groove107h, the fixed shaft end106ecan be rotated in the circumferential direction.

For this reason, the position in the axial direction of the electrostimulation block portion103during rotation can be stabilized. The operator operates the rotary member107C in the axial direction to move the electrostimulation block portion103in the axial direction, such that the placement in the axial direction of the electrostimulation block portion103in the vein inner wall Vscan be easily done.

In this modification, the circumferential groove107hmay be modified to a semicircular shape, a U shape, a V shape, or the like. The shape in side view is not limited to the T shape, and an appropriate key shape may be used.

Next, a fourth modification of the electrostimulation system of this embodiment will be described.

FIG. 10Ais a schematic perspective view showing a main part of a modification (fourth modification) of the rotary member and the electrode urging member in the electrostimulation system according to the first embodiment of the present invention.FIG. 10Bis a side view when viewed from a direction indicated by an arrow J ofFIG. 10A.

In this modification, as shown inFIGS. 10A and 10B, a rotary member107D and an electrostimulation block portion103D (electrostimulation block) are provided, instead of the rotary member107and the electrostimulation block portion103of the first embodiment.

The rotary member107D is provided with the engagement grooves107dof the rotary member107at three places or more.FIG. 10Ashows an example where the engagement grooves are provided at four places at regular intervals in the circumferential direction.

The electrostimulation block portion103D includes fixing hooks116R and116L (electrode urging member) which have a shape to be plane-symmetric in the same manner as the fixing hooks106R and106L, instead of the fixing hooks106R and106L of the electrostimulation block portion103.

The fixing hook116R (116L) includes a fixed shaft end116e(convex portion) which protrudes obliquely from the same position as the fixed shaft end106eoutward in the radial direction, an axial arm portion116dwhich extends from the leading end of the fixed shaft end116etoward the base end along the axial direction of the support103a, and an arcuate arm portion116cwhich is connected to the axial arm portion116dthrough an R-shaped bent portion and extends so as to overlap the arcuate arm portion106awhen viewed from the axial direction of the support103a, instead of the fixed shaft end106eand the arcuate arm portion106cof the fixing hook106R (106L). The arcuate arm portion116cand the hook leading end portion106bare connected to each other through a bent portion having an R shape in side view.

The length of the fixed shaft end116eis set to a length such that a gap which is slightly wider than a thickness of the tubular portion107aof the rotary member107D on the leading end side is formed between the support103aand the axial arm portion116d.

According to this modification, the engagement grooves107dat two adjacent places from among the engagement grooves107dat the four places are engaged with a pair of fixed shaft ends116e, such that, similarly to in the first embodiment, the electrostimulation block portion103D can be rotated.

At this time, the axial arm portion116d, which forms a gap slightly wider than the thickness of the tubular portion107aon the leading end side between the support103aand the axial arm portion116d, is connected to the fixed shaft end116e. Thus, the leading end of the rotary member107D is guided while being sandwiched by a pair of axial arm portions116das approaching the fixed shaft ends116e.

For this reason, even when the inner diameter of the through hole107cis greater than the outer diameter of the support103a, and there is a large amount of looseness in the radial direction, the position of the leading end of the rotary member107D is centered by the axial arm portions116din the vicinity of the fixed shaft ends116e. For this reason, it becomes more easy to engage the engagement grooves107dwith the fixed shaft ends116e.

In disengaging the rotary member107D in the circumferential direction after the rotary member107D has been engaged with the electrostimulation block portion103D, the rotary member107D is urged to the opposite side of the circumferential direction by the axial arm portions116d, such that the rotary member107D is disengaged in the circumferential direction.

At the leading end of the rotary member107D, since the engagement grooves107dare provided at the four places, the engagement grooves107dat two places closest to the positions of the fixed shaft ends116emay be engaged with the fixed shaft ends116e. For this reason, the rotary member107D can be engaged with the fixed shaft ends116ewith a smaller rotation amount on the average compared to the first embodiment.

In this modification, these are combined with each other, such that the engagement of the rotary member107D and the electrostimulation block portion103D can be done smoothly and rapidly.

Next, an electrostimulation system according to a second embodiment of the present invention will be described.

FIG. 11Ais a schematic sectional view showing a state when an electrostimulation system according to a second embodiment of the present invention is loaded in a superior vena cava.FIG. 11Bis a schematic perspective view of a K portion ofFIG. 11Aon a magnified scale.FIG. 12is a sectional view taken along the line L-L ofFIG. 11B.FIG. 13Ais a schematic front view of the electrostimulation system according to the second embodiment of the present invention.FIG. 13Bis a sectional view taken along the axial direction of an electrostimulation block which is used in the electrostimulation system according to the second embodiment of the present invention.

As shown inFIGS. 11A and 11B, in an electrostimulation system111of this embodiment, a pacing lead118is further provided, and instead of the electrostimulation lead102and the electrostimulation block portion103of the first embodiment, an electrostimulation lead112(sheathed conducting wire member) and an electrostimulation block portion113(electrostimulation block) are provided. Hereinafter, a description will be provided focusing on the differences from the first embodiment.

The electrostimulation lead112and the pacing lead118of the electrostimulation system111are electrically connected to an electrostimulation device1210through connectors104and118aprovided at the base end side thereof.

Similarly to the first embodiment, the electrostimulation lead112and the electrostimulation block portion113provided at the leading end of the electrostimulation lead112are inserted into the superior vena cava V1to apply the same electrical stimulus to the vagus nerve VN.

The pacing lead118applies electrical stimulus to the heart H from the electrode arranged in the heart H or detects electrical excitation.

Although the pacing lead118may have the common configuration of a type which is used in a heart treatment of the related art, hereinafter, as shown inFIG. 13A, an example has been described where a connector118a, a lead portion118b, a positive electrode118c, a blade-shaped member118e, and a negative electrode118dare provided in that order from the base end side.

Similarly to the connector104, the connector118amay be an IS1 connector or a waterproof connector in accordance with whether the electrostimulation device1210is provided inside or outside the body.

The lead portion118bis connected to the positive and negative electrodes of the connector118a. The lead portion118binsulates a pair of conducting wires, which are constituted by twisted wires made of for example, nickel-cobalt alloy, from each other, and insulates and sheathes the outer circumferential surfaces of the conducting wires. As the lead portion118b, for example, a polyurethane tube having two lumens may be used. The outer circumferential surface of the polyurethane tube may be subjected to thrombus prevention coating.

In this embodiment, the outer diameter of the lead portion118bis about φ1 mm.

The positive electrode118cand the negative electrode118dare respectively connected to the conducting wires which pass through the lead portion118b.

The surface of the negative electrode118dis subjected to porous platinum coating, porous iridium coating, iridium oxide coating, or titanium nitride coating. Thus, the electrode surface area increases compared to a case where no coating is carried out.

The electrode surface area is adjusted in such a manner, such that, in order to apply electrical stimulus from the negative electrode118dor to detect electrical excitation, biological impedance between the negative electrode118dand the positive electrode118cis adjusted to an appropriate value.

The blade-shaped member118eis a member for locking to the shape of the heart H, and is a blade-shaped protrusion which protrudes from the lead portion118bnear the negative electrode118doutward in the radial direction between the positive electrode118cand the negative electrode118d. Thus, a structure is formed such that the negative electrode118deasily comes into contact with a heart tissue.

In this embodiment, the circumscribed circle diameter of the leading end in the protrusion direction of the blade-shaped member118eis set so as not to exceed φ2 mm.

The pacing lead118passes through the electrostimulation lead112, is inserted into the superior vena cava V1, and is arranged such that the negative electrode118dcomes into contact with the inner wall of a right ventricle H1through a right atrium H3.

The electrostimulation device1210is provided with a connection terminal1200awhich is connected to the connector104to apply the same electrostimulation pulses as in the electrostimulation device1200of the first embodiment to the connector104, and a connection terminal1210bwhich is connected to the connector118ato transfer electrical signals between the negative electrode118dand the positive electrode118cof the pacing lead118.

Though not particularly shown, the electrostimulation device1210has a circuit which sends electrical stimulus to the electrostimulation lead112, a circuit which sends electrical stimulus to the pacing lead118, and a circuit which detects electrical excitation of the heart H transmitted through the positive electrode118cand the negative electrode118d.

The electrostimulation device1210is provided with a heart rate measurement section which measures the heart rate by using the pacing lead118, an electrostimulation pulse voltage supply section which supplies an electrostimulation pulse voltage to the electrostimulation lead112and the pacing lead118, and a control section which controls the supply of the electrostimulation pulse voltage on the basis of the state of the heart H.

The heart rate measurement section can detect the potential of the positive electrode118cwith respect to the potential of the negative electrode118dto obtain a potential change according to the electrical activity of the heart H, that is, an electrocardiographic signal. The heart rate measurement section can measure the heart rate from a time interval, in which the potential of the electrocardiographic signal or a change rate becomes greater than a predetermined threshold value, on the basis of the waveform of the obtained electrocardiographic signal.

When the heart H is in the bradycardiac state and the heart rate decreases, the electrostimulation pulse voltage supply section supplies the electrostimulation pulse voltage having comparatively large energy between the negative electrode118dand the positive electrode118cof the pacing lead118. Thus, the heart H is stimulated and the heart rate increases.

Meanwhile, similarly to the electrostimulation lead102of the first embodiment, the electrostimulation lead112is provided with a negative electrode105aand a positive electrode105b(seeFIGS. 13A and 13B). With this, when the heart H is in the tachycardiac state or the fibrillation state and the heart rate increases, the electrostimulation pulse voltage having comparatively small energy can be supplied between the negative electrode105aand the positive electrode105b. Thus, the vagus nerve VN in the vicinity of the superior vena cava V1is stimulated and the heart rate decreases.

Although the conditions for electrostimulation of the electrostimulation lead112and the pacing lead118are different, as the conditions, the magnitude of the electrostimulation pulse voltage, frequency, pulse width, stimulation end time, stimulation start time, stimulation duration time, electrostimulation stoppage, and the like are exemplified.

As shown inFIGS. 13A and 13B, the electrostimulation lead112includes a tubular sheathing member112a, instead of the sheathing member102cof the electrostimulation lead102of the first embodiment.

The tubular sheathing member112ais provided with a hollow portion112bwhich passes therethrough in the central portion in the radial direction of the sheathing member102c.

The outer diameter of the tubular sheathing member112ais of a size so as to pass through the through hole107cof the rotary member107, and in this embodiment, is φ2 mm.

In this embodiment, as the hollow portion112b, a cylindrical hole is used which has an inner diameter such that the pacing lead118excluding the connector118acan pass therethrough. In this embodiment, the inner diameter of the hollow portion112bis φ1.5 mm.

The conducting wires102aand102bwhich are introduced from the sheathing tube102dconnected to the base end of the electrostimulation lead112pass through the tubular sheathing member112ain a range of the thickness of the tubular sheathing member112a, are insulated from each other, and pass through the electrostimulation lead112in the axial direction without being exposed to the outer circumferential surface of the tubular sheathing member112aand the inner circumferential surface of the hollow portion112b.

The electrostimulation block portion113is provided with a tubular support113a, instead of the support103aof the electrostimulation block portion103of the first embodiment.

The tubular support113ais provided on the leading end side of the tubular sheathing member112a, and supports the electrode portion105and the fixing hooks106R and106L in the lateral surface. The tubular support113ahas passed therethrough the conducting wires102aand102bextending from the tubular sheathing member112ain a state of being insulated from each other and guides the conducting wires102aand102bto the electrode portion105. The tubular support113aincludes a hollow portion113b, which communicates with the hollow portion112band has the same diameter as the hollow portion112b, in the central portion thereof.

In this embodiment, the tubular support113ahas a columnar outer shape having the same diameter as the tubular sheathing member112a, and is formed of the same insulating material as the tubular sheathing member112aso as to be combined with the tubular sheathing member112a.

The electrode portion105and the fixing hooks106R and106L are provided in the tubular support113aat the same positions as the support103a.

As shown inFIG. 13B, similarly to the tubular sheathing member112a, the conducting wires102aand102bpass through the tubular support113ain a range of the thickness of the tubular support113aand are respectively electrically connected to the negative electrode105aand the positive electrode105b.

As described above, in the electrostimulation lead112and the electrostimulation block portion113of the embodiment, the tubular sheathing member112aand the tubular support113aare provided, and the hollow portions112band113bcommunicate with each other in the central portions, such that the pacing lead118can pass therethrough. This is different from the first embodiment.

For this reason, according to the electrostimulation system111, similarly to the first embodiment, the electrostimulation block insertion process can be performed in which the electrostimulation block portion113and the electrostimulation lead112are inserted into the superior vena cava V1through the rotary member107.

In the electrostimulation block insertion process of this embodiment, the pacing lead118passes through the hollow portion112band113bin the electrostimulation lead112and the electrostimulation block portion113which are inserted into the superior vena cava V1, such that the leading end portion of the pacing lead118can be inserted into the right ventricle H1and the positive electrode118cand the negative electrode118dcan be close to or come into contact with the inner wall of the right ventricle H1.

Next, the electrode alignment process can be performed in which the engagement grooves107dof the rotary member107are engaged with the fixed shaft ends106eto rotate the rotary member107, and the position in the circumferential direction of the electrostimulation block portion103is aligned in the vein inner wall Vs.

In this embodiment, since the pacing lead118is provided, the heart rate is monitored by using the pacing lead118while the electrostimulation pulses are applied to the electrostimulation lead112, making it possible to determine whether or not the electrode portion105is at the position facing the vagus nerve VN.

In order to facilitate the adjustment, the electrostimulation device1210may produce sound in accordance with the heart rate, and a change in the heart rate may be expressed by, for example, the high and low levels or the tone of sound. In this case, the operator can hear sound to confirm a change in the heart rate, efficiently advancing working. The heart rate may be displayed on a liquid crystal monitor or the like in the form of numerical value, graph, or the like.

Thus, as shown inFIGS. 11B and 12, the vagus nerve VN and the electrode portion105can be arranged to face each other with the vein sandwiched therebetween.

The connectors104and118aare connected to the electrostimulation device1210, such that electrical stimulus can be applied to the vagus nerve VN through the electrostimulation lead112, and electrical stimulus can be applied to the heart H or electrical excitation can be detected through the pacing lead118.

As described above, according to this embodiment, electrostimulation can be carried out for a linear tissue, such as a nervous tissue, placement can be made without causing damage to a nervous tissue as a target, and pacing or sensing of the heart H can be carried out along with electrostimulation to the nervous tissue.

In this embodiment, the pacing lead118is embedded in the electrostimulation lead112as a single body and can be inserted into the vein. For this reason, it is possible to reduce the number of vein insertion slots and to reduce blood flow inhibition since multiple leads are arranged in parallel in the vein.

Although in this embodiment, an example has been described where the pacing lead118is placed in the right ventricle H1, the pacing lead118may be formed as a single body with another lead placed in the right atrium H3, or another lead placed in a tubular vein of the surface layer of the left ventricle H2and the electrostimulation lead112may be formed as a single body. In this case, electrostimulation of a nervous tissue may be carried out on the basis of the electrocardiographic monitor of tissues in which these leads are placed.

Next, an electrostimulation system according to a third embodiment of the present invention will be described.

FIG. 14Ais a schematic partial sectional view taken along the axial direction of an electrostimulation system according to a third embodiment of the present invention.FIG. 14Bis a schematic perspective view of the leading end of a rotary member according to the third embodiment of the present invention.

As shown inFIGS. 14A and 14B, an electrostimulation system121of this embodiment includes an electrostimulation lead122(sheathed conducting wire member) an electrostimulation block portion123(electrostimulation block), and a rotary member127, instead of the electrostimulation lead102, the electrostimulation block portion103, and the rotary member107in the electrostimulation system101of the first embodiment. Hereinafter, a description will be provided focusing on the difference from the first embodiment.

The electrostimulation lead122is provided with a hollow portion122b, through which the rotary member127described below passes, inside the electrostimulation lead102of the first embodiment.

The electrostimulation block portion123includes a support123a, which has an angular groove portion123bat a position, at which the hollow portion122bcommunicates therewith, on the base end side of the support103a, instead of the support103aof the electrostimulation block portion103of the first embodiment.

The angular groove portion123bhas an elongated angular cross-section along one diameter of the hollow portion122band extends to the leading end side.

Similarly to the support103aof the first embodiment, the support123aincludes an electrode portion105and fixing hooks106R and106L (FIG. 14Ais a sectional view, thus the fixing hook106R is not shown). In this embodiment, however, the fixed shaft ends106ehave only a function as the fixed ends of the fixing hooks106R and106L, not having a function as a convex portion which is engaged with the rotary member.

The rotary member127is a flexible member which can pass through the hollow portion122b, and is constituted by a stylet which has a shaft portion127bhaving rigidity so as to transmit torque to the leading end side, a plate-shaped portion127a(engagement portion) provided to be inserted into the angular groove portion123bat the leading end of the shaft portion127band to be engageable in the circumferential direction, and a handle portion127crotating the shaft portion127bat the base end of the shaft portion127b.

The length of the shaft portion127bis set to a length such that the plate-shaped portion127ais insertable into the angular groove portion123bin a state where the handle portion127cis placed outside the body.

As the material of the shaft portion127b, for example, a superelastic wire made of nickel-titanium may be used. For example, in the case of the electrostimulation lead122in which the outer diameter of a hollow sheathing member122ais about φ2 mm, a superelastic wire having an outer diameter in a range of φ0.3 mm to φ1 mm is preferably used. Thus, satisfactory torque transmissibility can be obtained.

In this embodiment, since the shaft portion127bpasses through the hollow portion122b, the shaft portion127bdoes not come into contact with blood, the vein inner wall Vs, or the like. For this reason, the shaft portion127bmay be made of a material having no biocompatibility. Sheathing processing for biocompatibility or the like may be omitted.

Although in this embodiment, the handle portion127cis provided for ease of the rotation operation, when the rotation operation may be easily made even with no handle portion127cbecause of the shaft diameter of the shaft portion127bor the like, the handle portion127cmay not be provided.

In this embodiment, the angular groove portion123bas a groove portion is formed in the electrostimulation block portion123at a position inside the outer circumference of the electrostimulation lead122. The rotary member127is formed in a shaft shape so as to pass through the electrostimulation lead122, and has, at the leading end thereof, the plate-shaped portion127aas a convex portion which is provided to be engageable with the angular groove portion123bof the electrostimulation block portion123in the circumferential direction of rotation.

According to the electrostimulation system121of this embodiment, after the electrostimulation lead122is assembled in a state where the rotary member127passes through the hollow portion122band the plate-shaped portion127ais engaged with the angular groove portion123b, the electrostimulation block insertion step into the superior vena cava V1may be performed by using an introducer (not shown) of the related art with no engagement portions, such as the engagement grooves107dat the leading end, instead of the rotary member107of the first embodiment, in the same manner as in the first embodiment.

At this time, the operator operates the rotary member127straight, the electrostimulation block portion123and the electrostimulation lead122can be moved in the superior vena cava V1along the axial direction of the superior vena cava V1. For this reason, buckling rigidity of the electrostimulation lead122which is necessary for moving the electrostimulation block portion103in the vein in the axial direction in a state where the fixing hooks106R and106L are open may satisfy combined rigidity of the sheathing member122aand the rotary member127. In this way, a portion of rigidity of the electrostimulation lead122is imposed on the rotary member127, making it possible to achieve the reduction in the diameter of the hollow sheathing member122acompared to a case where no rotary member127is provided.

Next, the electrode alignment process is performed in which the electrostimulation block portion123in the vicinity of the vagus nerve VN is placed to face the vagus nerve VN in the superior vena cava V1.

In the electrode alignment process of this embodiment, the operator rotates the handle portion127c, such that torque is transmitted to the support123athrough the angular groove portion123bengaged with the plate-shaped portion127aof the rotary member127. Thus, the electrostimulation block portion123is rotated in the circumferential direction.

After the electrode alignment process ends, the rotary member127, and the introducer if necessary, is removed from the body, and the electrostimulation is carried out in the same manner as in the first embodiment.

As described above, according to the embodiment, as in the first embodiment, the electrostimulation block portion123can be aligned in the vein.

The veins have various sectional shapes, and there is also a vein which has a modified sectional shape far from a circular shape. The insertion length into the vein may be extended depending on the position of a nervous tissue.

Meanwhile, an introducer has an inner diameter significantly greater than the outer diameter of the electrostimulation lead122. For this reason, as in the first embodiment, if an introducer is used as the rotary member, frictional force in the vein may increase at the time of rotation, making it difficult to carry out rotation adjustment.

In this embodiment, in such a case, the rotary member127does not come into contact with the vein inner wall Vs, such that with friction against the hollow portion122b, rotation adjustment can be stably carried out without being influenced by the shape of the vein or the like. The electrostimulation lead122which rotates in the vein has a diameter smaller than the introducer, thus the frictional resistance decreases.

For this reason, it is possible to reduce a load imposed on a patient at the time of insertion or the placement time of the electrostimulation block portion123, and to improve the QOL (Quality of Life) of the patient.

Next, an electrostimulation system according to a fourth embodiment of the present invention will be described.

FIG. 15is a schematic partial sectional view taken along the axial direction of an electrostimulation system according to a fourth embodiment of the present invention.FIG. 16is a schematic perspective view showing a state where the electrostimulation system according to the fourth embodiment of the present invention is placed in a superior vena cava.

As shown inFIGS. 15 and 16, the electrostimulation system131of this embodiment includes an electrostimulation lead132(sheathed conducting wire member) and an electrostimulation block portion133(electrostimulation block), instead of the electrostimulation lead102and the electrostimulation block portion103in the electrostimulation system101of the first embodiment. Hereinafter, a description will be provided focusing on the differences from the first embodiment.

The electrostimulation lead132includes a sheathing member132c, instead of the sheathing member102cof the electrostimulation lead102of the first embodiment, and further includes, in the base end portion, a fluid supply tube132dwhich has a syringe connection connector132econnected to a syringe (not shown).

The syringe (not shown) is connected to the syringe connection connector132eand injects a fluid, such as a normal saline solution. The syringe connection connector132eis provided with a check valve, such that even when the syringe is pulled out after the normal saline solution is injected, the injected normal saline solution does not flow backward.

The sheathing member132cis configured such that a flow channel132fwhich communicates to the path in the fluid supply tube132dis provided to extend in the axial direction in a linear member formed of the same material as the sheathing member102cto have the same diameter as the sheathing member102c. Though not shown inFIG. 15, similarly to the sheathing member102c, the sheathing member132chas passed therethrough the conducting wires102aand102belectrically connected to the connector104.

The electrostimulation block portion133includes a support133a, a cylindrical protrusion133b(convex portion), and a cylindrical balloon136(electrode urging member), instead of the support103aand the fixing hooks106R and106L of the electrostimulation block portion103of the first embodiment.

The support133ais a shaft-like member which is provided on the leading end side of the sheathing member132c, and has an electrode portion105constituted by a negative electrode105aand a positive electrode105bin the lateral surface in the same manner as the support103a.

Cylindrical protrusions133bwhich protrude outwardly in the radial direction are respectively provided at the same positions as the fixed shaft ends106eof the first embodiment in the lateral surface on the based end side compared to the positive electrode105b.

In this embodiment, the support133ahas a columnar outer shape having the same diameter as the sheathing member132c, and is molded as a single body with the sheathing member132cby using the same insulating material as the sheathing member132c. The cylindrical protrusions133bare also formed as a single body.

Inside the support133a, the flow channel132fin the sheathing member132cextends and is opened toward the lateral surface opposite to the side, on which the negative electrode105aand the positive electrode105bare provided, at an intermediate position between the negative electrode105aand the positive electrode105bin the axial direction.

Though not particularly shown, similarly to the support103a, the conducting wires102aand102bwhich pass through the electrostimulation lead132are respectively electrically connected to the negative electrode105aand the positive electrode105b.

The cylindrical balloon136is a member which urges the electrode portion105of the electrostimulation block portion133inserted into the superior vena cava V1toward the vein inner wall Vs, and a fluid filling portion136cwhich communicates with the opening of the flow channel132fin the support133ais a saclike member which is formed of, for example, a thin film of silicone rubber.

The fluid filling portion136chas a shape to be cylindrically swollen when the fluid supplied through the flow channel132fis filled therein. In a state where the fluid is not filled, the fluid filling portion136chas a thin cylindrical shape and can be appropriately folded and deformed.

With regard to the shape of the cylindrical balloon136when swollen, the diameter (outer diameter) of an outer circumferential surface136ais set such that the electrode portion105comes into close contact with the vein inner wall Vsin the superior vena cava V1in which the electrostimulation block portion133is placed.

The diameter (inner diameter) of an inner circumferential surface136bis not particularly limited and is preferably as large as possible so as not to inhibit the blood flow. That is, the thickness of the fluid filling portion136cwhen swollen is preferably small. When another lead is inserted in parallel to the electrostimulation lead132, the inner diameter is set such that another lead passes therethrough.

The shape of the cylindrical balloon136when swollen depends on the diameter of the vein as an insertion target. For example, a thin cylindrical shape is preferably used which as an inner diameter of φ19 mm when the outer diameter is φ10 mm and an inner diameter of φ19 mm when the outer diameter is φ20 mm.

In this embodiment, the arrangement position of the cylindrical balloon136in the axial direction is set inside the negative electrode105aand the positive electrode105b.

According to such arrangement, even when the single cylindrical balloon136is provided, the negative electrode105aand the positive electrode105bcan substantially press the vein inner wall Vsequally. For this reason, it is possible to prevent the negative electrode105aand the positive electrode105bfrom floating from the vein inner wall Vs.

However, the cylindrical balloon136may be provided in a range so as to cover the negative electrode105aand the positive electrode105bin the axial direction, or the end portion on the base end side may be arranged closer to the base end compared to the positive electrode105b.

A plurality of cylindrical balloons136may be arranged, for example, at the positions facing the negative electrode105aand the positive electrode105b, and the flow channel132fmay branch off and communicate with the fluid filling portion136c.

As described above, in the electrostimulation system131, the electrode urging member is constituted by a cylindrical balloon whose outer diameter is enlargeable and reducible through fluid pressure.

A convex portion which is engaged with the rotary member107is constituted by a member different from the electrode urging member.

According to the electrostimulation system131, in a state where the fluid is not filled in the cylindrical balloon136, in the same manner as in the first embodiment, the electrostimulation block insertion process can be performed. That is, the electrostimulation block portion133and the electrostimulation lead132are inserted into the superior vena cava V1through the rotary member107. At this time, the cylindrical balloon136is folded inside the rotary member107, thereby easy insertion is achieved.

Next, the electrostimulation block portion133extends from the leading end of the rotary member107, and the normal saline solution is injected from the syringe connected to the syringe connection connector132e. The normal saline solution is supplied to the fluid filling portion136cof the cylindrical balloon136through the flow channel132f, and the cylindrical balloon136is swollen in a cylindrical shape. At this time, the injection amount of the normal saline solution should be limited such that too much urging force toward the vein inner wall Vsis not applied, so that the electrostimulation block portion133can go straight and rotate in the superior vena cava V1.

The cylindrical balloon136is swollen in such a state, such that the cylindrical balloon136is arranged in a cylindrical shape along the vein inner wall Vs, and the flow of blood is not inhibited because the central portion thereof is opened.

Since the injection amount of the normal saline solution into the cylindrical balloon136is small, the cylindrical balloon136has softness and flexibility, and even when there is unevenness or meandering in the vein, can be smoothly inserted into the vein.

Next, the electrode alignment process is performed. In this process, as in the first embodiment, the position of the electrostimulation lead132is fixed, the rotary member107is moved in the axial direction, and the engagement grooves107dare engaged with the cylindrical protrusions133bof the support133a. Thereafter, as in the first embodiment, the rotary member107is rotated while monitoring the electrocardiogram or the heart rate, such that the position of the electrostimulation block portion133in the circumferential direction is aligned in the vein inner wall Vs.

Thus, as shown inFIG. 16, the vagus nerve VN and the electrode portion105can be arranged to face each other with the vein sandwiched therebetween.

After the position of the electrostimulation block portion133in the circumferential direction is aligned, the normal saline solution is further injected from the syringe, such that the swollen amount of the cylindrical balloon136is maximized. Thus, the outer circumferential surface136aof the cylindrical balloon136urges the vein inner wall Vsand the lateral surface of the support133aon the rear side of the electrode portion105, the electrode portion105and the vein inner wall Vscome into close contact with each other, and the position of the electrostimulation block portion133with respect to the vein inner wall Vsis fixed. The rotary member107is withdrawn to the base end side and disengaged with the cylindrical protrusions133b.

Since the syringe connection connector132ehas the check valve, even when the injection of the normal saline solution stops and the syringe is removed, the shape of the cylindrical balloon136is maintained.

Next, as in the first embodiment, if necessary, the rotary member107is removed, and the electrostimulation process is further performed.

According to this embodiment, the cylindrical balloon136having excellent flexibility is used so as to be easily aligned with respect to veins of various sizes or modified cross-sections. Since the cylindrical balloon136is excellent in softness, there is no case where vascular endothelium is damaged at the time of insertion or placement.

A metallic mesh structure which is used in a stent may be provided on the outer circumference of the cylindrical balloon136. In this case, the position after the alignment in the vein can be more firmly stabilized.

Although in the above description, an example has been described where the electrostimulation block is provided at the leading end of the sheathed conducting wire member, the position of the electrostimulation block is not limited to the leading end and may be provided in the intermediate portion of the sheathed conducting wire member on the leading end side of the sheathed conducting wire member.

Although in the description of the first to third embodiments, an example has been described where the electrode urging member is constituted by an elastic member having an arc portion, the shape before deformation is not limited to the arc shape insofar as the electrode urging member is arranged in the circumferential direction of the vein, and urging can be done outwardly in the radial direction. For example, a curved shape which forms a portion of an ellipse, a parabola, a hyperbola, or the like may be used.

The shape of the electrode urging member in side view is not limited to the U shape, and may be, for example, a corrugated shape, an arc shape, a comb-teeth shape, or the like.

The electrode urging member is not limited to the linear elastic member, and may be an elastic member which comes into surface contact with the vein inner wall.

Although in the description of the fourth embodiment, an example has been described where the electrode urging member is a cylindrical balloon, the electrode urging member may have a shape, such as a C sectional shape.

Although in the description of the first embodiment or the like, an example has been described where the rotary member serves as an introducer having a check valve, the rotary member is not limited to an introducer insofar as the rotary member is arranged on the outer circumference of the sheathed conducting wire member and has a cylindrical shape with a base end portion extending outside the body, and an engagement mechanism rotating the electrostimulation block is provided in the vicinity of the leading end. For example, a guide sheath having no check valve may be used.

Although in the description of the third embodiment, an example has been described where the rotary member127is a solid shaft-like member, the rotary member which can pass through the sheathed conducting wire member may be a tubular member. For example, a tubular member with engagement grooves at the leading end may be used so as to be engaged with convex portions protruding toward the inner circumferential surface of the sheathed conducting wire member.

In this case, if a structure is made such that the hollow portion of the sheathed conducting wire member pass through the electrostimulation block, as in the second embodiment, the pacing lead and the like can pass through the hollow portion.

As a fifth embodiment of the present invention, an electrostimulation electrode assembly will be described which can be used in combination with the electrostimulation system according to each of the first to fourth embodiments of the invention.

FIG. 17Ais a schematic perspective view of an electrostimulation electrode assembly according to a fifth embodiment of the present invention.FIG. 17Bis a schematic perspective view showing a state where the electrostimulation electrode assembly according to the fifth embodiment of the present invention is loaded in a vein.FIG. 18Ais a sectional view taken along the line A-A ofFIG. 17A.FIG. 18Bis a sectional view taken along the line B-B ofFIG. 18A.FIG. 18Cis a diagram when viewed from a direction indicated by an arrow b ofFIG. 18A.FIG. 19Ais a schematic exploded perspective view showing a main part of the electrostimulation electrode assembly according to the fifth embodiment of the present invention.FIG. 19Bis a sectional view taken along the line C-C ofFIG. 19A.FIG. 20Ais a schematic sectional view showing a state where the electrostimulation electrode assembly according to the fifth embodiment of the present invention is loaded in a superior vena cava.FIG. 20Bis a sectional view taken along the line D-D ofFIG. 20A.

The drawings are schematic views, thus the shape or dimension is magnified (the same is applied to the following description).

As shown inFIGS. 17A,18A, and18B, an electrode stimulation lead201(electrostimulation electrode assembly) of this embodiment includes an electrode portion205, a support203which supports the electrode portion205in a state where a portion of the electrode portion205is exposed as an exposed electrode surface205a, conducting wires202aand202b(conducting wire member, seeFIG. 18A) which are electrically connected to the electrode portion205, a sheathing member202through which the conducting wires202aand202bpass, a connector209(terminal portion) which is electrically connected to the conducting wires202aand202bpassing through the sheathing member202, and an electrode urging member206which is fixed to the lateral surface of the support203.

The electrode stimulation lead201indirectly applies electrical stimulus to a biological tissue, such as a nervous tissue, through the inner wall of the vein. The electrostimulation lead201is used to be connected to a stimulus generation device (electrostimulation device1200or the like) (not shown) through the connector209provided on the base end side. The stimulus generation device may be implanted inside the body or may be provided outside the body, and a heart pacemaker, an implanted defibrillation device, a nervous stimulation device, a pain relief device, an epilepsy treatment device, a muscle stimulation device, and the like may be an exemplary example.

The electrode stimulation lead201of the embodiment can be particularly preferably used in a treatment to apply electrical stimulus to a nervous tissue in the vicinity of the heart, for example, a vagus nerve or the like.

For this reason, as shown inFIG. 17B, the electrode stimulation lead201is used in a state where the support203, the electrode urging member206, the leading end portion of the sheathing member202connected to the support203are inserted into or implanted in the vein, for example, the superior vena cava V1.

The electrode portion205is a metal portion which applies electrical stimulus through the inner wall of the vein, and as shown inFIGS. 18A and 18B, is constituted by an electrode pair of a negative electrode205A (electrode) electrically connected to the conducting wire202ainside the support203and a positive electrode205B (electrode) electrically connected to the conducting wire202binside the support203.

The material of the negative electrodes205A and the positive electrode205B is not particularly limited insofar as a metal has biocompatibility so as to be used in a state of being implanted in the biological body. Preferred examples of the material include noble metal materials having biocompatibility, such as a platinum-iridium alloy.

The shape of the negative electrode205A is not particularly limited insofar as the exposed electrode surface205awhich is exposed from the support203can smoothly come into close contact with the vein inner wall Vsand the shape can transmit sufficient electrostimulation energy to a nervous tissue or the like as a stimulation target in the vicinity of the vein inner wall Vsthrough the exposed electrode surface205a.

In this embodiment, the negative electrode205A is constituted by a block member which has a shape obtained by bisecting a columnar member along the center line, and is provided in the support203so as to be exposed from the semi-cylindrical surface of the exposed electrode surface205a. A fixed portion205bon the rear side of the exposed electrode surface205ais fixed in close contact with the support203. The diameter of the exposed electrode surface205ais the same as the outer diameter of the support203having a columnar shape.

The shape of the positive electrode20513is also not particularly limited insofar as the exposed electrode surface205awhich is exposed from the support203can smoothly come into close contact with the vein inner wall Vsand the shape can transmit sufficient electrostimulation energy to a nervous tissue or the like as a stimulation target in the vicinity of the vein inner wall Vsthrough the exposed electrode surface205a.

In this embodiment, the positive electrode205B is constituted by a block member having the same shape as the negative electrode205A.

The positive electrode205B is provided on the support203at a position distant from the negative electrode205A toward the base end such that the exposed electrode surface205aturns in the same direction as the negative electrode205A. Similarly to the negative electrode205A, a fixed portion205bon the rear side of the exposed electrode surface205ais fixed in close contact with the support203.

For this reason, as shown inFIG. 18C, the exposed electrode surfaces205ain plan view (when viewed from a direction indicated by an arrow b ofFIG. 18A) are arrayed in a direction along the central axis O3of the support203, and the center lines of the exposed electrode surfaces205aare arrayed on a center line O5parallel to the central axis O3.

The dimension of the negative electrode205A and the positive electrode205B can be appropriately set insofar as appropriate electrical stimulus can be applied from the vein inner wall Vsto a nervous tissue in the vicinity of the vein inner wall Vs. As an example of specific dimension, when the outer diameter of the support203is φ2.0 mm, the length in the axial direction of each exposed electrode surface205ais 2 mm, the diameter of the exposed electrode surface205ais φ2.0 mm, and the gap (separation interval) in the axial direction between the negative electrode205A and the positive electrode205B is 5 mm.

The support203is a member which is pressed in close contact with the vein inner wall Vsalong with the exposed electrode surfaces205aexposed from the surface when inserted inside the vein and placed, and is formed of a material having electrical insulation. The support203is preferably formed of a material having high biocompatibility so as to be implanted in the biological body for a long time. Silicone resin, polyurethane, and fluorine resin are exemplary examples thereof. Examples of fluorine resin include a tetrafluoroethylene-ethylene copolymer (ETFE), polytetrafluoroethylene (PTFE), and the like.

The surface of the support203is preferably subjected to thrombus preventing coating.

In this embodiment, the support203has a columnar outer shape having the same diameter as the outer diameter of each exposed electrode surface205aof the electrode portion205. An aperture shape in which the negative electrode205A and the positive electrode205B are provided is formed in the lateral surface of the intermediate portion in the axial direction. Two through holes through which the conducting wires202aand202bconnected to the negative electrode205A and the positive electrode205B pass to the base end side under insulated condition are provided inside the support203along the axial direction.

For this reason, as shown inFIG. 18B, the sectional shape of the support203of this embodiment is a semicircular shape to be plane-symmetric to the negative electrode205A or the like. As a result, the support203is provided in a shape to entirely cover the negative electrode205A and the positive electrode205B when viewed from the rear sides of the exposed electrode surfaces205a.

As shown inFIGS. 19A and 19B, a leading end-side fixed portion204A and a base end-side fixed portion204B are fixed to the outer circumferential portions of the leading end portion and the base end portion of the support203to fix the electrode urging member206.

The leading end-side fixed portion204A and the base end-side fixed portion204B are thin cylindrical members which have, in the intermediate portion, a support connection portion204aas a through hole for fixing to the outer circumferential surface of the support203, and in the lateral surface on the leading end side thereof, a hook fixing portion204bis provided which is an aperture portion for inserting the electrode urging member206thereinto and fixing the electrode urging member206.FIG. 19Ais a schematic view, thus the dimension is magnified. Actually, a step between the leading end-side fixed portion204A and the base end-side fixed portion204B and the outer circumferential surface of the support203is configured to be sufficiently small so as to smoothly come into close contact with the vein inner wall Vs. For example, when the outer diameter of the support203is φ2.0 mm, the outer diameter of each of the leading end-side fixed portion204A and the base end-side fixed portion204B is preferably about φ2.0 mm.

As the material of the leading end-side fixed portion204A and the base end-side fixed portion204B, an appropriate resin material or a metal material having biocompatibility may be used.

As a method of fixing the leading end-side fixed portion204A and the base end-side fixed portion204B to the support203, an appropriate fixing method, such as bonding, welding, pressing, or swaging, may be used depending on the materials.

The conducting wire202ais a liner or coil-like conductor which electrically connects the terminal for a negative electrode of the connector209and the negative electrode205A. The shape or material of the conducting wire202ais not particularly limited insofar as the conducting wire202ais resistant to bending in the vein into which the electrode stimulation lead201is inserted. In this embodiment, for example, a twisted wire made of a nickel-cobalt alloy is used.

The conducting wire202bis a liner or coil-like conductor which electrically connects the terminal for a positive electrode of the connector209and the positive electrode205B. With regard to the conducting wire202b, the same shape and material as the conducting wire202amay be used. In this embodiment, for example, a twisted wire made of a nickel-cobalt alloy is used.

The conducting wires202aand202bare guided toward the base end of the support203by the support203in a state of being insulated from each other, extend outside the support203, and pass through the sheathing member202, one end portion of which is connected to the base end portion of the support203.

The sheathing member202is a member which has a linear shape to pass through the vein, and one end portion of which (the leading end portion of the sheathing member202) is connected to the support203, ensuring that the conducting wires202aand202bextending from the support203pass therethrough in an insulation state and guided to the other end portion thereof.

The outer shape in the sectional shape of the sheathing member202is not particularly limited insofar as the sheathing member202can pass through the vein, and a shape, such as a circular shape, an elliptical shape, an oval shape, or an approximate shape may be used. A lumen through which a catheter-like linear member passes may be provided.

In this embodiment, the sectional shape of the sheathing member202is a circular shape, and the outer diameter thereof is set to a diameter sufficiently smaller than the inner diameter of the vein so as not to inhibit the blood flow at the time of insertion into the vein. In this embodiment, the outer diameter is φ2.0 mm which is the same as the diameter of the support203.

The sheathing member202is made of a material having electrical insulation, flexibility, and biocompatibility in the vein. For example, the same material as the support203may be used. The outer surface of the sheathing member202may be subjected to thrombus prevention coating.

Although the sheathing member202and the support203may be connected to the leading end side and the base end side as separate members, in this embodiment, the sheathing member202is molded as a single body with the support203.

As shown inFIG. 17A, the connector209is provided in the other portion of the sheathing member202. Though not particularly shown, the end portions of the conducting wires202aand202bhaving passed through the sheathing member202are respectively electrically connected to the terminal for a negative electrode and the terminal for a positive electrode of the connector209.

As the connector type of the connector209, an appropriate connector type may be used in accordance with the shape of the connection terminal of the stimulus generation device (not shown).

For example, when the stimulus generation device is provided inside body, an IS1 connector may be used. The IS1 connector includes a negative electrode, a positive electrode, and a rubber ring for maintaining the connection of the terminal for a negative electrode and the terminal for a positive electrode watertight.

When the stimulus generation device is provided outside the body, a waterproof connector may be used which includes a terminal for a negative electrode and a terminal for a positive electrode.

As shown inFIGS. 17A and 17B, the electrode urging member206urges the electrode portion205exposed from the support203toward the vein inner wall Vs. In this embodiment, the electrode urging member206is constituted by a fixing hook206R and a fixing hook206L.

In this embodiment, the fixing hooks206R and206L are formed by bending a linear elastic member in a U shape (angulated U shape) as a whole, and have arcuate arm portions206aand206c(curved portions or linear curved bodies) and a hook leading end portion206b(leading end connection portion).

The fixing hooks206R and206L are formed and arranged so as to be plane-symmetric with respect to a plane including the center line O5, which is common to the exposed electrode surfaces205aof the negative electrode205A and the positive electrode205B arrayed in the axial direction of the support203, and the central axis O3of the support203. The fixing hook206R is located on the right when viewed from the base end side of the support203to the leading end side in a state where the exposed electrode surface205aof the electrode portion205turns upward, and the fixing hook206L is located on the left side in the same manner.

As shown inFIG. 19B, the fixing hooks206R and206L of this embodiment are constituted by linear members which have a sheathed layer208formed on the outer circumferential surface of a linear elastic body207made of an appropriate elastic material to press the vein inner wall Vsby elastic restoring force. In this embodiment, the cross-section of the linear elastic body207has a circular shape, and the sheathed layer208is formed concentrically.

The linear elastic body207is preferably formed of an elastic material such that the elastic material has flexibility to be a little folded at the time of insertion into the vein, and the shape which can urge the inner wall of the vein in the vein can be restored. Examples of the material includes superelastic alloy, such as nickel-titanium alloy, having shape reversibility to be easily elastically deformed by external force and to easily return to the state before deformation if external force is eliminated. In this embodiment, for example, a member which is substantially by molding a superelastic wire having a diameter φ0.3 mm made of a nickel-titanium-based alloy in a U shape.

As the sheathed layer208, polyurethane tube coating or fluorine resin tube coating may be used. For this reason, the linear elastic body207does not come into direct contact with blood in the vein or the vein inner wall Vs. Polyurethane or fluorine resin has small frictional resistance against the vein inner wall Vs, allowing smooth sliding along the vein inner wall Vs.

Similarly to the sheathing member202, the tube constituting the sheathed layer208is preferably subjected to thrombus prevention coating.

The sheathed layer208is not limited to tube coating, and may be formed by carrying out lubricating coating for the surface of the linear elastic body207.

Hereinafter, unless particularly noted, the shape common to the fixing hooks206R and206L will be described on the basis of the shape in the natural state where no external force is applied.

The arcuate arm portion206aprotrudes from the leading end side compared to the negative electrode205A in the lateral surface of the support203, and is a curved portion which forms an arc to obliquely protrude outward in the radial direction and to be bent toward the opposite side to the direction in which each exposed electrode surface205aof the electrode portion205is formed.

As shown inFIG. 17A, when each exposed electrode surface205aof the electrode portion205turns upward, the arcuate arm portion206aprotrudes from the lower lateral surface compared to the electrode surface of the negative electrode205A.

On the base end side in the protrusion direction of the arcuate arm portion206a, as shown inFIG. 19A, a fixed end portion206dis provided which is bent toward the base end along the axial direction of the support203so as to be inserted into and fixed to the hook fixing portion204bof the leading end-side fixed portion204A fixed to the support203.

The average radius of curvature of the arcuate arm portion206ais set to be greater than the radius of the inner wall portion of the vein as an insertion target, for example, the vein inner wall Vsof the superior vena cava V1.

The length of the arcuate arm portion206ais equal to or greater than ¼ of the circumferential length of the vein inner wall Vsat the position where the support203is provided. That is, the arcuate arm portion206aof the fixing hook206R and the arcuate arm portion206aof the fixing hook206L have a length equal to or greater than ¼ of the circumferential length of the vein inner wall Vs. Thus, the total length of the arcuate arm portions206aof the fixing hooks206R and206L is equal to or greater than half of the circumferential length of the vein inner wall Vs. For this reason, if curvature is made along the vein inner wall Vs, a major arc shape is formed in the vein inner wall Vs.

The curved shape of the arcuate arm portion206ais not limited to an arc shape, and an arc shape which forms a portion of an ellipse, a parabola, a hyperbola, or the like may be used insofar as the shape can be curved along the vein inner wall Vs.

The arcuate arm portion206cprotrudes from the base end side compared to the positive electrode20513in the lateral surface of the support203, and is a curved portion which forms an arc to obliquely protrude in the same direction as the arcuate arm portion206aoutward in the radial direction and to be bent toward the opposite side to the direction in which each exposed electrode surface205aof the electrode portion205is formed.

The protrusion position and the curved shape of the arcuate arm portion206cin the circumferential direction of the lateral surface of the support203are set so as to overlap the arcuate arm portion206awhen viewed from the axial direction of the support203.

As shown inFIG. 19A, on the base end side in the protrusion direction of the arcuate arm portion206c, a fixed end portion206eis provided which is bent toward the base end along the axial direction of the support203so as to be inserted into and fixed to the hook fixing portion204bof the base end-side fixed portion204B fixed to the support203.

The hook leading end portion206bis a linear portion which connects the leading ends of the arcuate arm portions206aand206cin the protrusion direction and extends along the axial direction of the support203. Both end portions of the hook leading end portion206band the leading ends of the arcuate arm portions206aand206cin the protrusion direction form corner portions having an R shape. Thus, the fixing hooks206R and206L can come into smooth contact with and slide along the vein inner wall Vs.

The fixing hooks206R and206L are arrayed on the curved surface having a diameter greater than the vein inner wall Vslaterally extending from the lateral surface of the support203in an assembled state where the fixed end portions206dand206eare fixed to the leading end-side fixed portion204A and the base end-side fixed portion204B. That is, a pair of arcuate arm portions206aand a pair of arcuate arm portions206cextend toward both lateral sides of the support203in an arc shape such that the direction in which the exposed electrode surface205ais formed is made convex when viewed from the axial direction of the support203. Each opening has a U shape to be connected to the lateral surface of the support203in plan view.

Thus, if the support203is inserted into the superior vena cava V1, as shown inFIGS. 17B and 20A, the fixing hooks206R and206L are deformed in a direction in which the radius of curvature of the curved portion decreases to be elastically deformed along the vein inner wall Vs, and can urge the vein inner wall Vsoutward in the radial direction in accordance with the deformation amount.

Next, the action of the electrode stimulation lead201will be described in connection with, for example, an operation to apply electrical stimulus from the superior vena cava V1to the vagus nerve VN.

As shown inFIGS. 20A and 20B, the vagus nerve VN is in the vicinity of the superior vena cava V1. For this reason, if each exposed electrode surface205aof the electrode portion205is at the position facing the vagus nerve VN with the vein inner wall Vssandwiched therebetween, it is possible to indirectly apply electrical stimulus to the vagus nerve VN through the vein of the superior vena cava V1.

First, as shown inFIG. 17B, the operator makes an incision on the skin in the cervical region to form an incision portion CL in the superior vena cava V1.

Next, the operator inserts a tubular member (not shown), which is used to insert a catheter-like member, such as an introducer or a guide sheath, into the vein, into the incision portion CL, and the leading end of the tubular member is located in the vicinity of the vein inner wall Vsparallel to the vagus nerve VN.

Next, the electrode stimulation lead201is inserted into the tubular member from the leading end side.

At this time, since the fixing hooks206R and206L are excellent in flexibility, if the support203is inserted into the tubular member, bending deformation occurs in a range of a gap between the support203and the tubular member, and the support is folded. The fixing hooks206R and206L are constituted by a linear member which is bent so as to have an R shape in the corner portions, do not have a shape to be caught by the inner circumferential surface of the tubular member. Thus, the fixing hooks206R and206L can smoothly slide in the axial direction in a folded state.

The operator further inserts the electrode stimulation lead201to protrude the electrode stimulation lead201from the leading end opening of the tubular member inward of the superior vena cava V1. When the support203at the leading end emerges from the tubular member, external force from the tubular member is not applied to the folded fixing hooks206R and206L, such that the fixing hooks206R and206L try to return to the shape in the natural state.

The shape in the natural state of each of the fixing hooks206R and206L is greater than the inner diameter of the vein inner wall Vsof the superior vena cava V1. For this reason, as shown inFIGS. 17B and 20A, the fixing hooks206R and206L come into contact with the vein inner wall Vsand urge the vein inner wall Vsoutward in the radial direction.

In the cross-section perpendicular to the central axis Ovof the vein inner wall Vs, the arcuate arm portions206aand206cof the fixing hooks206R and206L have a length equal to or greater than half of the circumferential length of the vein inner wall Vsin total, thereby reliably urging the electrode portion205in the support203outward in the radial direction. For this reason, the electrode portion205is urged toward the vein inner wall Vsalong with the support203, and each exposed electrode surface205acomes into close contact with the vein inner wall Vs.

At this time, since the radius of curvature of the exposed electrode surface205ais smaller than the radius of curvature of the vein inner wall Vs, the exposed electrode surface205abites into and comes into close contact with the vein inner wall Vs.

In this way, the fixing hooks206R, the support203including the electrode portion205, and the fixing hook206L are placed along the vein inner wall Vs. For this reason, the flow of blood in the superior vena cava V1is not easily inhibited. As a result, even when the electrode stimulation lead201is placed in the vein, it is possible to suppress the occurrence of thrombus in the vicinity of the electrode portion205.

The position of the electrode portion205in the vein is maintained uniformly by urging force of the fixing hooks206R and206L.

Since the support203is provided to cover the entire electrode portion205from the rear side of the exposed electrode surface205a, the exposed electrode surface205afaces the vein inner wall Vsand is exposed outward in the radial direction.

In this way, the electrode portion205is fixed in close contact with the vein inner wall Vsin the vicinity of the vagus nerve VN. The tubular member which is used at the time of insertion is, for example, torn or the like and removed outside the vein or the body.

Next, the connector209is connected to the stimulus generation device to apply electrostimulation pulses set in advance from the stimulus generation device. Thus, electrostimulation energy emitted from the electrode portion205is emitted toward the vein inner wall Vsand transmitted to the vagus nerve VN in the vicinity of the vein through the vein. As a result, the vagus nerve VN is indirectly electrically stimulated.

At this time, blood between the exposed electrode surface205aand the vein inner wall Vsis easily excluded by urging force from the electrode urging member206. For this reason, electrostimulation energy from the exposed electrode surface205acan be transmitted to the vein inner wall Vsand applied to the vagus nerve VN outside the vein.

Since the exposed electrode surface205afaces the vein inner wall Vsand is exposed only outward in the radial direction, it is possible to reduce leakage of electrostimulation energy into blood. For this reason, stable electrostimulation can be carried out even at a low voltage.

In this embodiment, physical stress is not applied to a nervous tissue at all, and there is no case where the tissue is damaged due to ischemia.

Although a nervous tissue is very soft and easily damaged compared to other biological tissues, according to the electrode stimulation lead201of this embodiment, it is possible to reliably prevent such damage.

Since the electrode portion205is not in direct contact with the nervous tissue, there is no case where, when the electrode portion205is pressed, a foreign-body reaction occurs in the vicinity of the nervous tissue or fibrous capsule formation occurs. For this reason, biological impedance after the electrode portion205is placed is stabilized.

Thus, since the electrostimulation can be carried out without applying excessive electrostimulation energy, the possibility that the nervous tissue is damaged due to electrostimulation energy is significantly reduced.

Since the electrode portion205is stably supported in the vein by the electrode urging member206, there is no case where the stimulation position of the electrode portion205is shifted.

As described above, according to the electrode stimulation lead201of this embodiment, the electrode can be placed in the superior vena cava by a transvenous approach. Thus, it is possible to carry out electrode placement in a very short time, to carry out electrode placement under local anesthesia, and to reduce a load imposed on a patient, compared to a case, for example, the electrode is placed in a nervous tissue by a trocar from a pleural cavity or a thoracotomy.

Next, first and second modifications of the electrostimulation electrode assembly of this embodiment will be described.

In these modification, only the shape of the electrode portion205which is used in the electrode stimulation lead201of the fifth embodiment and correspondingly the shape of the support203are changed. Hereinafter, a description will be provided focusing on the differences from the fifth embodiment.

FIGS. 21A and 21Bare schematic sectional views showing first and second modifications of the electrostimulation electrode assembly according to the fifth embodiment of the invention.

An electrode250of the first modification may be used in place of each of the negative electrode205A and the positive electrode205B of the electrode portion205of the fifth embodiment. As shown inFIG. 21A, the electrode250has a shape in which one surface of a rectangular parallelepiped projects in a cylindrical dome shape, and a fixed portion250bwhich is the other rectangular parallelepiped portion is provided in the support203such that the projected cylindrical surface constitutes an exposed electrode surface250a.

The diameter of the exposed electrode surface250ais set to be the same as the outer diameter of the support203.

For this reason, the exposed electrode surface250aconstitutes a circumferential surface in which a minor arc having a circumferential angle smaller than 180° extends in one direction.

Similarly to the exposed electrode surface205aof the fifth embodiment, the exposed electrode surface250aof this modification is configured such that entire electrode250is covered with the support203when viewed from the rear side of the exposed electrode surface250a.

The exposure length of the exposed electrode surface250ain the circumferential direction is shorter than the exposed electrode surface205a. For this reason, even with weak urging force compared to the fifth embodiment, the exposed electrode surface250acan be reliably brought into contact with the vein inner wall Vs.

The outer circumferential surface of the support203surrounding the outer circumference of the exposed electrode surface250acan be reliably brought into contact with the vein inner wall Vs, making it possible to further reduce leakage of a current into blood at the time of electrostimulation.

In forming the exposed electrode surface250a, the shape of the fixed portion250bis not limited to a U shape which constitutes a portion of the rectangular parallelepiped. For example, the fixed portion250bmay have a V sectional shape. A reverse T shape or an arrow shape protruding downward in the drawing may be provided or an external screw shape or a multi-ring shape may be provided in the outer circumferential portion such that the withdrawal resistance outward in the radial direction with respect to the support203increases.

As shown inFIG. 21B, an electrode251of the second modification includes a cylindrical dome-shaped exposed electrode surface251ahaving curvature smaller than the outer diameter of the support203, in place of the exposed electrode surface250aof the electrode250of the first modification. Hereinafter, a description will be provided focusing on the differences from the first modification.

Though not particularly shown, in the end portion of the exposed electrode surface251ain the depth direction of the drawing, an inclined portion or an R shape is preferably provided to be smoothly connected to the outer circumferential surface of the support203.

The inclined portion or the R shape may be provided by inclining or curving the end portion of the exposed electrode surface251aor may be provided by raising a portion of the outer circumferential surface of the support203toward the exposed electrode surface251a.

According to this modification, the exposed electrode surface205ais formed as a convex surface having curvature smaller than the support203, making it possible to further improve contact with the vein inner wall Vs.

Even when the electrode width in the circumferential direction is the same as the exposed electrode surface250aof the first modification, it is possible to increase the electrode area.

Next, a third modification of the electrostimulation electrode assembly of this embodiment will be described.

FIG. 22Ais a schematic sectional view showing a third modification of the electrostimulation electrode assembly according to the fifth embodiment of the invention.FIGS. 22B,22C, and22D are diagrams when viewed from a direction indicated by an arrow E ofFIG. 22A.

In this modification, as shown inFIGS. 22A and 22B, an electrical insulating protrusion portion203ais provided in the outer circumferential portion of the exposed electrode surface250aof the first modification so as to protrude in an elliptical dome shape or a spherical shape from the surface of the support203outward in the radial direction. Hereinafter, a description will be provided focusing on the difference from the first modification.

The protrusion portion203ais preferably formed as a single body with the support203.

For example,FIG. 22Bshows a case where the protrusion portions203aare provided at four places in total by two places in the axial direction along the outline in the circumferential direction of the exposed electrode surface250a. However, the number of protrusion portions203aor the arrangement positions are not particularly limited. For example, the protrusion portion may be provided in the vicinity of the end surface in the axial direction of the exposed electrode surface250a.

According to this modification, the protrusion portion203acomes into contact with the vein inner wall Vs, making it possible to further stabilize the position of the electrode250with respect to the vein inner wall Vs.

The protrusion portion203aprotrudes outwardly in the radial direction compared to the exposed electrode surface250ain the vicinity of the outer edge portion of the exposed electrode surface250a, thus the protrusion portion203abecomes a wall portion having electrical insulation with respect to the outer edge portion of the exposed electrode surface250a. For this reason, the protrusion portion203ahas a function of reducing leaking of a current at the time of electrostimulation.

In this modification, in order to further increase the current leakage prevention effect, like a linear protrusion203band a revolving protrusion203cshown inFIGS. 22B and 22C, a linear protrusion may be provided to extend along the outer edge portion of the exposed electrode surface250a.

The linear protrusion203bis a linear protrusion portion which extends in parallel to the outer edge portions on both sides of the exposed electrode surface250ain the circumferential direction. In this case, it becomes easier to prevent misalignment of the exposed electrode surface250ain the circumferential direction, making it possible to further reduce current leakage in the circumferential direction.

The revolving protrusion203cis a linear protrusion portion which is provided to surround the exposed electrode surface250aalong the whole circumference of the outer edge portion of the exposed electrode surface250a. In this case, it becomes easier to prevent misalignment of the exposed electrode surface250ain the circumferential direction and the axial direction, making it possible to reduce current leakage toward the whole circumference of the exposed electrode surface250a.

Next, a fourth modification of the electrostimulation electrode assembly of this embodiment will be described.

FIG. 23is a schematic sectional view showing a fourth modification of the electrostimulation electrode assembly according to the fifth embodiment of the invention.

An electrode252of this modification may be used in place of each of the negative electrode205A and the positive electrode205B of the electrode portion205of the fifth embodiment. As shown inFIG. 23, the electrode252is a substantially cylindrical member which has a through hole252cin the center portion thereof. In the outer circumferential surface of the electrode252, an exposed electrode surface252ahaving the same semi-cylindrical shape as the exposed electrode surface205aand an outer circumference fixed portion252b, which is constituted by a semi-cylindrical surface having a diameter smaller than the exposed electrode surface252aare provided. Hereinafter, a description will be provided focusing on the differences from the fifth embodiment.

The outer circumference fixed portion252bis covered with the support203. For this reason, the electrode252is apparently the same as negative electrode205A and the positive electrode205B of the fifth embodiment.

In this modification, since the electrode252is molded as a single body with the support203, the material of the support203is filled in the through hole252c, such that the electrode252is firmly fixed to the support203.

However, the electrode252may be fixed to the support203by the outer circumference fixed portion252band the through hole252cmay be made hollow. When a coil-like conducting wire is used as the conducting wire202aor the like, the through hole252cmay be used as a conducting wire connection portion with which the coil-like conducting wire is internally engaged for connection.

Next, a fifth modification of the electrostimulation electrode assembly of this embodiment will be described.

FIG. 24Ais a schematic plan view showing a fifth modification of the electrostimulation electrode assembly according to the fifth embodiment of the present invention.FIG. 24Bis a diagram when viewed from a direction indicated by an arrow F ofFIG. 24A.

As shown inFIGS. 24A and 24B, an electrode stimulation lead211(electrostimulation electrode assembly) of this modification includes an electrode urging member260, in place of the electrode urging member206of the electrode stimulation lead201of the fifth embodiment. Hereinafter, a description will be provided focusing on the differences from the fifth embodiment.

The electrode urging member260is constituted by fixing hooks260R and260L which are linear members bent along the axis lines similarly to the fixing hooks206R and206L of the fifth embodiment, and the wire diameter of the fixing hooks260R and260L in the axial direction is changed.

That is, the fixing hook260R (260L) includes an arcuate arm portion260awith a gradually decreasing wire diameter from the base end portion fixed to the leading end-side fixed portion204A in the protrusion direction toward the leading end in the protrusion direction, in place of the arcuate arm portion206a. The fixing hook260R (260L) also includes an arcuate arm portion260cwhich a gradually decreasing wire diameter from the base end portion fixed to the base end-side fixed portion204B in the protrusion direction toward the leading end in the protrusion direction, in place of the arcuate arm portion206c.

The leading end portions of the arcuate arm portions260aand260cin the protrusion direction are connected to each other by a linear hook leading end portion260bwhich extends along the axial direction of the support203, in place of the hook leading end portion206b.

The fixing hooks260R and260L may be manufactured by a molded product of a superelastic wire or a molded product made of the same resin material as the support203.

According to this modification, urging force toward the vein inner wall Vscan be adjusted by appropriately changing the wire diameter of the fixing hooks260R and260L. For example, a bias of pressing force in the circumferential direction of the vein inner wall Vscan be reduced or a uniform pressure distribution can be achieved. A shape in which the blood flow is not easily inhibited may be obtained by reducing the diameter of a portion which does not contribute to an urging force.

Next, a sixth modification of the electrostimulation electrode assembly of this embodiment will be described.

FIG. 25is a schematic plan view showing a sixth modification of the electrostimulation electrode assembly according to the fifth embodiment of the present invention.

As shown inFIG. 25, an electrode stimulation lead212(electrostimulation electrode assembly) of this modification includes an asymmetrical electrode urging member261(electrode urging member), in place of the electrode urging member206of the electrode stimulation lead201of the fifth embodiment. Hereinafter, a description will be provided focusing on the differences from the fifth embodiment.

The asymmetrical electrode urging member261includes a U-shaped fixing hook261R, in place of the fixing hook206R of the fifth embodiment.

The U-shaped fixing hook261R has a curved portion261awhich projects in a U shape from the leading end-side fixed portion204A toward the base end-side fixed portion204B in plan view and is curved in the same arc shape as the fixing hook206R, in place of the arcuate arm portion206a, the hook leading end portion206b, and the arcuate arm portion206cof the fixing hook206R.

With this configuration, the shape of the asymmetrical electrode urging member261when viewed from the axial direction of the support203is a bilaterally symmetrical arc shape, and the shape in plan view is bilaterally asymmetrical with the support203sandwiched therebetween.

According to this modification, since the asymmetric electrode urging member261is provided, for example, in observing the electrode stimulation lead212inserted into the vein by using, for example, a two-dimensional image of an X-ray camera or the like, with the asymmetry of the asymmetrical electrode urging member261, it becomes easy to recognize the arrangement, movement direction, and the like of the support203or the electrode portion205.

Next, a seventh modification of the electrostimulation electrode assembly of this embodiment will be described.

FIG. 26Ais a schematic perspective view showing a seventh modification of the electrostimulation electrode assembly according to the fifth embodiment of the present invention.FIG. 26Bis a plan view when viewed from a direction indicated by an arrow G ofFIG. 26A.

As shown inFIGS. 26A and 26B, an electrode stimulation lead213(electrostimulation electrode assembly) of this modification includes an electrode urging member262, in place of the electrode urging member206of the electrode stimulation lead201of the fifth embodiment. Hereinafter, a description will be provided focusing on the differences from the fifth embodiment.

The electrode urging member262includes fixing hooks262R and262L having a shape to be plane-symmetric, in place of the fixing hooks206R and206L of the fifth embodiment.

The fixing hook262R (262L) includes curved arm portions262A and262C, in place of the arcuate arm portions206aand206cof the fixing hook206R (206L).

The curved arm portion262A is a linear portion which has a bent portion262bbent in a angulated U shape or a U shape toward the base end of the support203in the intermediate portion of the arcuate arm portion206ain the protrusion direction. Thus, the arcuate arm portion206ais divided into an arcuate portion262a(curved portion) which is connected to the leading end-side fixed portion204A and one end portion of the bent portion262band an arcuate portion262c(curved portion) which is connected to the other end portion of the bent portion262b.

The curved arm portion262C is a linear portion which has a bent portion262fbent in a U shape toward the leading end of the support203in the intermediate portion of the arcuate arm portion206cin the protrusion direction. Thus, the arcuate arm portion206cis divided into an arcuate portion262g(curved portion) which is connected to the base end-side fixed portion204B and one end portion of the bent portion262fand an arcuate portion262e(curved portion) which is connected to the other end portion of the bent portion262b.

In this modification, the bent portions262band262fare provided at positions facing each other along the axial direction of the support203. The bent portions262band262fare curved so as to overlap the arc shapes of the arcuate arm portions206aand206cwhen viewed from the axial direction of the support203. For this reason, when curved in the vein, the bent portions262band262fentirely come into contact with the vein inner wall Vs.

According to this modification, the arcuate portions262aand262cof the curved arm portion262A are arrayed on the axis of the same arc shape in the natural state but are connected to each other through the bent portion262b, such that, if external force is applied to the hook leading end portion206band deflective deformation occurs, deformation is easily made by torsional deformation of the bent portion262b. For this reason, when the same external force is applied to the hook leading end portion206b, the deformation amount increases compared to the beam-like arcuate arm portion206aextending in an arc shape.

The curved arm portion262A has small elastic restoring force compared to the arcuate arm portion206a, such that urging force toward the vein inner wall Vsis reduced.

The same is applied to the curved arm portion262C.

As described above, according to this modification, urging force of the electrode urging member toward the vein inner wall Vscan be changed without changing the wire diameter of a linear elastic member and without changing the circumferential length of a protruding arcuate portion.

Since the bent portions262band262fof the fixing hooks262R and262L entirely come into contact with the vein inner wall Vs, urging force of the fixing hooks262R and262L is two-dimensionally dispersed on the vein inner wall Vs. The contact between the fixing hooks262R and262L and the vein inner wall Vsis improved, and urging force toward the vein inner wall Vsis dispersed. For this reason, excessive urging force toward the vein inner wall Vsis not easily generated.

In this modification, since the bent portions262band262fare provided in the intermediate portions of the curved arm portions262A and262B, when the fixing hooks262R and262L are folded in the tubular member at the time of insertion into the vein, the curved arm portions262A and262B are easily bending-deformed in the bent portions262band262f. For this reason, accommodation in the tubular member is facilitated.

Next, an eighth modification of the electrostimulation electrode assembly of this embodiment will be described.

FIG. 27Ais a schematic perspective view showing an eighth modification of the electrostimulation electrode assembly according to the fifth embodiment of the present invention.FIG. 27Bis a side view when viewed from a direction indicated by an arrow H ofFIG. 27A.FIG. 27Cis a side view when viewed from a direction indicated by an arrow J ofFIG. 27A.

As shown inFIGS. 27A,27B, and27C, an electrode stimulation lead214(electrostimulation electrode assembly) of this modification includes an electrode urging member263, in place of the electrode urging member206of the electrode stimulation lead201of the fifth embodiment. Hereinafter, a description will be provided focusing on the differences from the fifth embodiment.

The electrode urging member263includes fixing books263R and263L having a shape to be plane-symmetric, in place of the fixing hooks206R and206L of the fifth embodiment.

The fixing hook263R (263L) includes a leading end connection portion263a, in place of the hook leading end portion206bof the fixing hook206R (206L).

As shown inFIG. 27B, the leading end connection portion263ahas a shape which is bent so as to protrude outward in the radial direction from a cylindrical curved surface in which the arcuate arm portions206aand206cas curved portions are arrayed.

In this modification, for example, as shown inFIG. 27B, the leading end connection portion263ais curved in a chevron shape in a direction of approaching the support203between the connection portions to the arcuate arm portions206aand206c, and a bent portion263bis formed at the vertex of the chevron shape. When viewed from the axial direction of the support203, the bent portion263bprotrudes outward in the radial direction from the curved surface in which the arcuate arm portions206aand206care arrayed.

The fixing hook263R (263L) is constituted by a linear portion which is substantially bent in an M shape.

According to this modification, when the fixing hook263R (263L) comes into contact with the vein inner wall Vs, as shown inFIG. 27B, in the leading end portions of the arcuate arm portions206aand206cin the protrusion direction, that is, in the connection portions to the bent portion263b, external force is applied from the vein inner wall Vsin a direction indicated by an arrow Q1to cause deformation, and reactive force R1is applied to the vein inner wall Vs.

Meanwhile, before coming into contact with the intermediate portions of the arcuate arm portions206aand the206c, the vein inner wall Vscomes into contact with the bent portion263bof the leading end connection portion263a, such that external force is applied from the vein inner wall Vsin a direction indicated by an arrow Q2to cause deformation, and reactive force R2is applied to the vein inner wall Vs.

For this reason, although in the hook leading end portion206bof the fifth embodiment, reactive force by deflection of the arcuate arm portions206aand206cis merely transmitted, with regard to the leading end connection portion263aof this modification, reactive force R2by deformation of the leading end connection portion263ais added to urging force which is applied to the vein inner wall Vs.

For this reason, it is possible to improve urging force compared to the fifth embodiment.

The fixing hook263R (263L) comes into contact with the vein inner wall Vsin an M shape, making it possible to improve contact with the vein inner wall Vs.

In this modification, since the bent portion263bis provided in the intermediate portion of the leading end connection portion263a, when the fixing hooks263R and263L are folded in the tubular member at the time of insertion into the vein, the leading end connection portion263ais easily bending-deformed in the bent portion263b. For this reason, accommodation in the tubular member is facilitated.

Next, a ninth modification of the electrostimulation electrode assembly of this embodiment will be described.

FIG. 28is a schematic perspective view showing a ninth modification of the electrostimulation electrode assembly according to the fifth embodiment of the present invention.

As shown inFIG. 28, an electrode stimulation lead215(electrostimulation electrode assembly) of this modification includes an electrode urging member264, in place of the electrode urging member206of the electrode stimulation lead201of the fifth embodiment. Hereinafter, a description will be provided focusing on the differences from the fifth embodiment.

The electrode urging member264includes fixing hooks264R and264L having a shape to be plane-symmetric, in place of the fixing hooks206R and206L of the first embodiment.

The fixing hook264R (264L) includes a plate-shaped curved hook264awhich is substantially curved in a cylindrical shape. The sectional shape of the plate-shaped curved hook264acoincides with the shape which is drawn by the axis of each of the arcuate arm portion206a, the hook leading end portion206b, and the arcuate arm portion206cof the fixing hook206R (206L). That is, each plate-shaped curved hook264ais a curved plate which extends from the lateral surface of the support203toward the lateral direction with the negative electrode205A and the positive electrode205B sandwiched therebetween, and the shape when viewed from the axial direction of the support203is an arch shape which is curved from the exposed electrode surface205aof each of the negative electrode205A and the positive electrode20513toward the rear side of the exposed electrode surface205a.

The plate-shaped curved hook264amay be manufactured by, for example, a molded product of a superelastic alloy or a molded product made of the same resin material as the support203. When a resin material is used, the plate-shaped curved hook264amay be molded as a single body with the support203.

In this modification, each plate-shaped curved hook264ais rolled and arranged along the lateral surface of the support203so as to be inserted into the vein through the tubular member. After insertion, when protruding from the tubular member, each plate-shaped curved hook264ais restored to the shape before rolling and presses the vein inner wall Vsoutward in the radial direction, such that the vein inner wall Vsis urged and the position of the electrode portion205is fixed.

According to this modification, the fixing hooks264R and264L come into plane contact with the vein inner wall Vs, such that the position of the electrode portion205is fixed. Thus, the contact to the vein inner wall Vsis improved, and urging force toward the vein inner wall Vsis dispersed. For this reason, excessive urging force toward the vein inner wall Vsis not easily generated.

Next, a tenth modification of the electrostimulation electrode assembly of this embodiment will be described.

FIG. 29is a schematic perspective view showing a tenth modification of the electrostimulation electrode assembly according to the fifth embodiment of the present invention.FIGS. 30A and 30Bare schematic sectional views illustrating the effect of the tenth modification of the electrostimulation electrode assembly according to the fifth embodiment of the present invention.

As shown inFIG. 29, an electrode stimulation lead216(electrostimulation electrode assembly) of this modification includes a leading end-side electrode urging member265A and a base end-side electrode urging member265B as an electrode urging member, in place of the electrode urging member206of the electrode stimulation lead201of the fifth embodiment. Hereinafter, a description will be provided focusing on the differences from the fifth embodiment.

The leading end-side electrode urging member265A is configured such that the fixing hooks206R and206L are respectively fixed to the support203as the leading end side of the electrode portion205by the leading end-side fixed portion204A and the base end-side fixed portion204B.

The base end-side electrode urging member265B is configured such that the fixing hooks206R and206L are respectively fixed to the support203as the leading end side of the electrode portion205by the leading end-side fixed portion204A and the base end-side fixed portion204B.

The leading end-side electrode urging member265A and the base end-side electrode urging member265B are provided at overlapping positions when viewed from the axial direction of the support203and arrayed in one curved surface.

According to this modification, the leading end side and the base end side of the electrode portion205of the support203are urged by the leading end-side electrode urging member265A and the base end-side electrode urging member265B which are different electrode urging members. For this reason, since the support203is fixed at two places on both end sides, each exposed electrode surface205aof the electrode portion205is not easily separated from the vein inner wall Vs.

For example, as shown inFIG. 30A, if the sheathing member202is separated to the center of the vein V, the base end side of the support203is caught by the sheathing member202and separated from the vein inner wall Vs. At this time, since the base end-side electrode urging member265B is provided which urges the vein inner wall Vsonly on the base end side of the support203, it is possible to prevent the base end side of the support203from being separated. At this time, since an influence of separation of the sheathing member202is not easily transmitted to the leading end-side electrode urging member265A, even if the fixing of the base end-side electrode urging member265B is loosened, the leading end-side electrode urging member265A can support the support203such that misalignment or the like does not occur.

Meanwhile, as shown inFIG. 30B, in the fifth embodiment, if the sheathing member202is separated, external force is transmitted to the leading end side of the support203through the arcuate arm portion206c, the hook leading end portion206b, and the arcuate arm portion206aof the electrode urging member206, and affects the fixed state on the base end side of the support203. For this reason, there is an influence of external force, such as separation of the sheathing member202, compared to this modification.

As described above, a plurality of electrode urging members may be provided along the axial direction of the support203. Although in this modification, an example has been described where two electrode urging members are provided, two or more electrode urging members may be provided. For example, the same electrode urging member may also be provided between the negative electrode205A and the positive electrode205B, such that three electrode urging members may be provided in total.

Next, an eleventh modification of the electrostimulation electrode assembly of this embodiment will be described.

FIG. 31is a schematic perspective view showing an eleventh modification of the electrostimulation electrode assembly according to the fifth embodiment of the present invention.

As shown inFIG. 31, an electrode stimulation lead217(electrostimulation electrode assembly) of this modification includes a leading end-side electrode urging member266A and a base end-side electrode urging member266B as an electrode urging member, in place of the electrode urging member206of the electrode stimulation lead201of the fifth embodiment. Hereinafter, a description will be provided focusing on the differences from the fifth embodiment.

The leading end-side electrode urging member266A includes arm-like fixing hooks266R and266L with a spherical contact portion266bat the leading end of the arcuate arm portion206awhile the hook leading end portion206band the arcuate arm portion206cof the fixing hooks206R and206L are eliminated.

The base end-side electrode urging member266B is configured such that arm-like fixing hooks266R and266L are fixed to the base end-side fixed portion204B in the same manner as the leading end-side fixed portion204A.

The leading end-side electrode urging member266A and the base end-side electrode urging member266B are provided at overlapping positions when viewed from the axial direction of the support203and arrayed in one curved surface.

According to this modification, a plurality of electrode urging members can be constituted by an arm-like extended member with simple configuration. For this reason, manufacturing is facilitated. The member is easily deformed at the time of insertion into the tubular member, and accommodation in the tubular member is facilitated.

Since the attachment width is reduced, when the length of the support203is identical, for example, the number of electrode urging members in the axial direction easily increases compared to the tenth modification.

Since the spherical contact portion266bis provided, the leading ends of the arm-like fixing hooks266R and266L come into smooth contact with the vein inner wall Vs, thereby reducing the load imposed on the vein inner wall Vs.

Next, an electrostimulation electrode assembly according to a sixth embodiment of the present invention will be described. Similarly to the electrostimulation electrode assembly of the fifth embodiment, the electrostimulation electrode assembly of this embodiment can be used in combination with the electrostimulation system according to each of the first to fourth embodiments of the invention.

FIG. 32Ais a schematic perspective view of a main part of an electrostimulation electrode assembly according to a sixth embodiment of the invention.FIG. 32Bis a partial enlarged view ofFIG. 32A.FIG. 33Ais a sectional view taken along the line K-K ofFIG. 32B.FIG. 33Bis a sectional view taken along the line L-L ofFIG. 32B.FIG. 33Cis a sectional view taken along the line M-M ofFIG. 32B.FIG. 33Dis a sectional view taken along the line N-N ofFIG. 32B.FIG. 33Eis a sectional view taken along the line P-P ofFIG. 32B.FIG. 34is a schematic perspective view of an elastic body which is used in the electrostimulation electrode assembly according to the sixth embodiment of the present invention.FIG. 35is a schematic sectional view showing the connection structure of a conducting wire member in the electrostimulation electrode assembly according to the sixth embodiment of the present invention.FIG. 36is a schematic sectional view showing a state where the electrostimulation electrode assembly according to the sixth embodiment of the present invention is loaded in a superior vena cava.

As shown inFIGS. 32A and 32B, an electrode stimulation lead221(electrostimulation electrode assembly) of this embodiment includes a sheathing member222, in place of the support203and the sheathing member202of the electrode stimulation lead201of the fifth embodiment, and as in the fifth embodiment, the leading end-side fixed portion204A and the base end-side fixed portion204B are fixed in the leading end portion of the sheathing member222. In place of the fixing hooks206R and206L, an electrode support portion267is provided which includes an electrode portion254having a negative electrode254A (electrode) and a positive electrode254B (electrode) and an electrode portion255having a negative electrode255A (electrode) and a positive electrode255B (electrode). Hereinafter, a description will be provided focusing on the differences from the fifth embodiment.

The sheathing member222is a linear portion which is formed of the same material as the sheathing member202of the fifth embodiment, and has passed therethrough a plurality of conducting wires224a,224b,225a, and225b(conducting wire member, seeFIG. 35) in the axial direction to provide electrical conduction between the electrode portions254and255and the connector209(not shown).

However, the connector209of the embodiment is provided with a plurality of electrode terminals corresponding to the number of electrode portions254and255.

The electrode support portion267includes electrode-equipped fixing hooks267R and267L which are linear portions bent in the same shape as the fixing hooks206R and206L.

Each of the electrode-equipped fixing hooks267R and267L include an arcuate support267a, a hook leading end portion267b, and an arcuate support267cto correspond to the arcuate arm portion206a, the hook leading end portion206b, and the arcuate arm portion206c. The arcuate support267ais provided with the negative electrodes254A and255A, and the arcuate support267cis provided with the positive electrodes254B and255B.

The internal structure of the electrode-equipped fixing hook267R (267L) is as shown inFIGS. 33A,33B,33C,33D, and33E. That is, a sheathing tube280, a coil conducting wire273, and a sheathing tube281are laminated on the outer circumferential portions of linear elastic bodies270and271as a core member in a concentric layer shape.

The electrode-equipped fixing hooks267R and267L are fixed to the leading end-side fixed portion204A and the base end-side fixed portion204B with the positional relationship so as to be plane-symmetric to one cross-section including the central axis of the leading end portion of the sheathing member222. For this reason, similarly to the fixing hooks206R and206L, the electrode-equipped fixing hooks267R and267L are bent in an arc shape when viewed from the axial direction of the sheathing member222and arrayed in one curved surface as a whole.

As shown inFIG. 34, the linear elastic body270includes a fixed end portion270cand an arcuate arm portion270awhich are bent in the same manner as the fixed end portion206dand the arcuate arm portion206ain the fixing hook206R (206L). A linear portion270bhaving a length half of the hook leading end portion206bis fixed to the leading end portion of the arcuate arm portion270ain the protrusion direction in the same manner as the hook leading end portion206b.

The linear elastic body271includes a fixed end portion271cand an arcuate arm portion271awhich are bent in the same manner as the fixed end portion206eand the arcuate arm portion206cin the fixing hook206R (206L). A linear portion271bhaving a length half of the hook leading end portion206bis connected to the leading end portion of the arcuate arm portion271ain the protrusion direction in the same manner as the hook leading end portion206b.

The leading end portions of the linear portions270band271bin the extension direction face each other in the axial direction and are connected coaxially by a shaft-like insulating connection member272having electrical insulation.

Thus, the linear elastic bodies270and271constitute a core member which is bent in the same manner as the fixing hook206R (206L) as a whole.

The linear elastic bodies270and271are made of an elastic material having the same conductivity as the linear elastic body206of the fifth embodiment.

As shown inFIGS. 32B and 33A, the sheathing tube280sheathes the outer circumferential portion of the linear elastic body270(271) and is made of the same electrical insulating material as the sheathed layer208of the fifth embodiment.

On the leading end side of the arcuate arm portion270a(271a) in the protrusion direction, the negative electrode254A (positive electrode254B) is provided.

The negative electrode254A (positive electrode254B) is substantially made of the same cylindrical member as the electrode252according to the fourth modification of the fifth embodiment. That is, as shown inFIG. 33B, a through hole254cis provided in the central portion, and in the outer circumferential surface of the negative electrode254A (positive electrode254B), a semi-cylindrical exposed electrode surface254ahaving the same diameter as the outer diameter of the sheathing tube280and an outer circumference fixed portion254bconstituted by a semi-cylindrical surface having a diameter smaller than the exposed electrode surface254aare provided.

The exposed electrode surface254ais exposed toward the lateral surface in the convex direction of curvature of the electrode-equipped fixing hook267R (267L).

The linear elastic body270(271) passes through the through hole254c. The through hole254cis connected to the outer circumferential surface of the linear elastic body270(271) by, for example, welding, swaging, or the like. Thus, the exposed electrode surface254ais also electrically connected to the linear elastic body270(271).

With this configuration, the negative electrode254A (positive electrode254B) is supported by the sheathing tube280having electrical insulation in a state where a portion thereof is exposed from the surface as the exposed electrode surface254a. For this reason, the sheathing tube280constitutes a support of the negative electrode254A (positive electrode254B).

On the base end side of the arcuate arm portion270a(271a) in the protrusion direction, the negative electrode255A (positive electrode255B) is provided at a position distant from the negative electrode254A (positive electrode25413).

The negative electrode255A (positive electrode255B) is substantially made of the same cylindrical member as the electrode252according to the fourth modification of the fifth embodiment. That is, as shown inFIG. 33D, a through hole255chaving a diameter greater than the sheathing tube280is provided in the central portion, and on the outer circumferential surface of the negative electrode255A (positive electrode255B), a semi-cylindrical exposed electrode surface255aand an outer circumference fixed portion255bmade of a semi-cylindrical surface having a diameter smaller than the exposed electrode surface255aare provided.

The exposed electrode surface255ais exposed toward the lateral surface in the convex direction of curvature of the electrode-equipped fixing hook267R (267L).

The coil conducting wire273, through which the sheathing tube280passes, passes through the through hole255c. The through hole255cis connected to the outer circumferential surface of the coil conducting wire273by, for example, welding, swaging, or the like. Thus, the exposed electrode surface255ais also electrically connected to the coil conducting wire273.

The coil conducting wire273extends to the base end side of the linear elastic body270in the protrusion direction and the fixed end portion270c(271c) in a state of being in close contact with the outer circumferential surface of the sheathing tube280.

As the material of the coil conducting wire273, an appropriate elastic material having conductivity may be used insofar as the material is resistant to bending of the arcuate arm portion270a(271a) in the vein.

As shown inFIGS. 32A,33C, and33D, the sheathing tube281sheathes the sheathing tube280or the outer circumferential portion of the coil conducting wire273which passes through the sheathing tube280in the arcuate arm portion270a(271a) in a range between the negative electrode254A (positive electrode254B) and the negative electrode255A (positive electrode255B) and from the end portion of the negative electrode255A (positive electrode255B) on the fixed end portion270c(271c) side to the fixed end portion270c(271c).

The sheathing tube281is made of the same electrical insulation material as the linear elastic body207of the fifth embodiment.

As shown inFIG. 33D, the sheathing tube281is provided so as to cover the outer circumference fixed portion255bof the negative electrode255A (positive electrode255B) at the position corresponding to the negative electrode255A (positive electrode255B).

With this configuration, the negative electrode255A (positive electrode255B) is supported by the sheathing tube281having electrical insulation in a state where a portion thereof is exposed from the surface as the exposed electrode surface255a. For this reason, the sheathing tube281constitutes a support of the negative electrode255A (positive electrode255B).

As shown inFIG. 35, the end portion of the fixed end portion270c(271c) is fixed to the hook fixing portion204bin a state where the outer circumferential surface of the fixed end portion270c(271c) and the outer circumferential surface of the coil conducting wire273are exposed in the radial direction.

The fixed end portion270c(271c) and the coil conducting wire273are electrically connected to a plurality of conducting wires which pass through the sheathing member222.

For example, the fixed end portion270c(271c) which is in the conduction state to the negative electrode254A (255A) is connected to the conducting wire224a(224b) which is in the conduction state to the terminal for a negative electrode of the connector209. The coil conducting wire273which is in the conduction state to the positive electrode254B (255B) is connected to the conducting wire225a(225b) which is in the conduction state to the terminal for a positive electrode of the connector209.

For this reason, the linear elastic body270(271) and each coil conducting wire273are electrically connected to the electrodes in the support and constitute a conducting wire member which extends outside the support.

The electrode stimulation lead221configured as above can be inserted into the vein, such as the superior vena cava V1, by using an appropriate tubular member in the same manner as in the fifth embodiment. As shown inFIG. 36, the leading end portion of the electrode stimulation lead221inserted into the superior vena cava V1presses the vein inner wall Vsto urge the vein inner wall Vsoutward in the radial direction because the electrode-equipped fixing hook267R (267L) is opened toward the vein inner wall Vs.

Urging force at this time is defined by elastic restoring force from elastic deformation of the linear elastic body270(271) and elastic deformation of each coil conducting wire273.

For this reason, the linear elastic body270(271) and each coil conducting wire273are connected to the support to constitute an electrode urging member which urges the electrode exposed from the support toward the inner wall of the vein.

At the time of urging, the exposed electrode surfaces254aand255aof the electrodes are exposed toward the lateral surface in the convex direction of curvature of the electrode-equipped fixing hook267R (267L). For this reason, the exposed electrode surfaces254aand255aface the vein inner wall Vsand are pressed into close contact with the vein inner wall Vs. The rear sides of the exposed electrode surfaces254aand255aare covered by the sheathing tubes280and281as a support over the entire region of the electrode.

For this reason, as in the fifth embodiment, the electrode can be inserted into the vein, and the electrode can be urged toward the inner wall of the vein and attached in the vein. Thus, it is possible to carry out electrostimulation indirectly through the vein without being in direct contact with the nervous tissue.

In this embodiment, the electrode-equipped fixing hook267R (267L) comes into close contact with the vein inner wall Vsalong the circumferential direction of the vein inner wall Vs, and has a plurality of electrodes which can apply electrical stimulus independently each other. For this reason, it is possible to change an electrostimulation position in the circumferential direction of the vein without rotating the position of the electrode-equipped fixing hook267R (267L) in the circumferential direction by selecting an electrode for applying electrical stimulus.

For this reason, even when the electrode support portion267is shifted from a predetermined position, an electrode near the predetermined position can be selected and electrostimulation can be carried out. Even when it is necessary to correct misalignment, the amount of shift of the electrode support portion267in the circumferential direction decreases, such that the placement of the electrode support portion267can be rapidly done.

For example, as shown inFIG. 36, when the electrode support portion267is provided inside the superior vena cava V1, the electrode portion255of the electrode-equipped fixing hook267R is arranged at a position substantially facing the vagus nerve VN, and the electrode portion255of the electrode-equipped fixing hook267L is arranged at a position substantially facing a phrenic nerve PN in the vicinity of the vagus nerve VN.

In such a case, the vagus nerve VN can be stimulated by the electrode portion255of the electrode-equipped fixing hook267R without stimulating the phrenic nerve PN. The phrenic nerve PN can be stimulated by the electrode portion255of the electrode-equipped fixing hook267L without stimulating the vagus nerve VN.

A single electrode stimulation lead221may be arranged to apply different electrical stimuli to the vagus nerve VN and the phrenic nerve PN simultaneously. For this reason, it is possible to reduce time and labor at the time of insertion and also to reduce the number of leads in the vein. Therefore, the blood flow is not easily inhibited, and it is possible to suppress the occurrence of thrombus.

Although in the above description, an example has been described where the electrostimulation electrode assembly stimulates the vagus nerve VN or the phrenic nerve PN, the electrostimulation electrode assembly may apply electrical stimulus to any nervous tissue insofar as the nervous issue is in the vicinity of the vein, and is not limited to the purpose for electrostimulation treatment of the vagus nerve VN or the phrenic nerve PN.

Although in the above described, an example has been described where an electrode urging member is fixed by using the leading end-side fixed portion204A and the base end-side fixed portion204B, this is just an example of the method of fixing the electrode urging member, and the fixing method is not limited.

For example, the end portion of the electrode urging member may be brought into close contact with the lateral surface of the support, and the end portion may be swaged or bonded on the outer circumference of the support. The end portion of the electrode urging member may be molded as a single body with the support and fixed to the support. A tubular attachment portion may be provided in the end portion of the electrode urging member, and the support may be externally engaged with and fixed to the attachment portion.

Although in the above description, an example has been described where the cross-section of the support has a circular shape, the support is not limited to a circular sectional shape insofar as the shape can come into close contact with the vein inner wall Vsalong with the electrode. For example, a shape having an elliptical cross-section, an oval cross-section, a rectangular cross-section, an arcuate cross-section, or the like may be used. The support is not limited to a columnar shape and may have a plate shape, a block shape, or the like.

Although in the above description, an example has been described where the electrode portion is constituted by an electrode the pair of negative electrode and the positive electrode, a counter electrode for electrostimulation may be provided separately from the electrostimulation electrode assembly, and then electrostimulation may be carried out. In this case, the electrostimulation electrode assembly may have only one electrode.

Although in the above description, an example has been described where the electrode urging member is connected to the support at the position with the exposed electrode surface sandwiched therebetween in the extension direction of the support, the position of the electrode urging member in the extension direction of the support is not particularly limited insofar as the exposed electrode surface can be urged toward the inner wall of the vein.

For example, the electrode urging member may be connected to the support at the same position as the exposed electrode surface in the extension direction of the support. Specifically, the arm-like fixing hook of the eleventh modification may be configured to extend from the support laterally to the exposed electrode surface.

The electrode urging member may be provided at the position sandwiched between two exposed electrode surfaces in the extension direction of the support.

Although in the above-description, an example has been described where the support connection portion204aof the leading end-side fixed portion204A is constituted by the through hole, a non-through hole may be used.

For example, a leading end-side fixed portion240A shown inFIG. 37may be used. That is, only a pair of hook fixing portions204bare provided on the leading end side of the leading end-side fixed portion240A, and an aperture portion240ais provided in the central portion on the base end side of the leading end-side fixed portion240A so as to be formed to the intermediated portion of the leading end-side fixed portion240A in the axial direction. In this case, a protrusion portion2100which will be engaged with the aperture portion240ais provided in the leading end portion of the support203, and the protrusion portion2100is engaged with the aperture portion240a, such that the support203and the leading end-side fixed portion240A are mechanically fastened to each other.

With this configuration, the outer diameter of the leading end-side fixed portion240A can be closer to the outer diameter of the support203or can be set to be equal to or smaller than the outer diameter of the support203. For example, the dimensional relationship can be established that the outer diameter of the support203is φ1.9 mm and the outer diameter of the leading end-side fixed portion240A is φ2.0 mm. In this way, the outer diameter of the support203and the outer diameter of the leading end-side fixed portion240A are substantially the same, making it possible to reduce the gap between the negative electrode205A and the positive electrode205B and the vein inner wall due to the difference in the outer diameter between the negative electrode205A and the positive electrode205B fitted to the outer diameter of the support203and the leading end-side fixed portion240A, thus reliably transmitting electrical stimulus.

Although in the above description, an example has been described where the outer shape of each of the leading end-side fixed portion204A and the base end-side fixed portion204B is a circular shape, the outer shape of each of the leading end-side fixed portion204A and the base end-side fixed portion204B is not limited to a circular shape.

For example, like a leading end-side fixed portion241A and a base end-side fixed portion241B shown inFIG. 38, an elliptical cylindrical shape may be used in which the direction in which the exposed electrode surface205agoes forward becomes a minor axis. In the major-axis direction of the leading end-side fixed portion241A and the base end-side fixed portion241B, the same hook fixing portions204bas described above may be provided.

In this case, when the minor axis of each of the leading end-side fixed portion241A and the base end-side fixed portion241B is close to the outer diameter of the support203, it is possible to reduce a step with respect to the support203. Therefore, it is possible to reduce the gap between the negative electrode205A and the positive electrode205B and the vein inner wall due to the step between the negative electrode205A and the positive electrode205B fitted to the outer diameter of the support203and the leading end-side fixed portion241A and the base end-side fixed portion241B. As a result, it is possible to reliably transmit electrical stimulus.

As a seventh embodiment of the invention, a biological implantable electrode which can be used in combination with the electrostimulation system according to each of the first to fourth embodiments of the present invention will be described with reference toFIGS. 39 to 45.FIG. 39is a perspective view showing a biological implantable electrode301of this embodiment. The biological implantable electrode301is placed in the vein to apply electrical stimulus to a target tissue in the vicinity of the vein. The biological implantable electrode301includes an elongated conducting wire sheathing body310, an electrode portion320which is provided on the leading end side of the conducting wire sheathing body310, an electrode support330which is provided in the vicinity of the electrode portion320, and a withdrawal portion (deformation mechanism)340which is used to remove the biological implantable electrode301.

The conducting wire sheathing body310includes conducting wires (not shown), and an insulating layer311which sheathes the circumference of the conducting wires. The two conducting wires are provided for the plus and minus sides, and stranded wires made of, for example, a nickel-cobalt alloy may be used. As the material of the insulating layer311, a polymer material having biocompatibility, such as polyurethane, silicone, or ETFE, may be used. In this embodiment, the insulating layer311is a tube made of polyurethane, and two conducting wires made of nickel-cobalt alloy pass through the lumen so as not to be short-circuited.

Like the biological implantable electrode301which is placed in the vein, if necessary, the outer surface of the insulating layer311may be subjected to coating for thrombus prevention. As the material of coating, an MPC polymer or the like may be used.

The conducting wire of the conducting wire sheathing body310is connected to an electrical stimulus generation device1200(not shown) or the like on the base end side on which no electrode portion320is provided. For ease of connection, if necessary, a connector or the like may be provided on the base end side of the conducting wire sheathing body310.

The electrode portion320applies electrical stimulus to a biological tissue, and is constituted by a plus electrode321on the leading end side and a minus electrode322on the base end side from the plus electrode321. The plus electrode321and the minus electrode322are formed on the outer surface of the conducting wire sheathing body310and are respectively connected to the plus conducting wire and the minus conducting wire of the conducting wire sheathing body310. Examples of the material of the electrode portion320include platinum, stainless steel, gold, silver, titanium, conductive oxides of the metals, and the like. From the viewpoint of a place where the electrode portion320comes into contact with the biological body, a noble metal having biocompatibility, such as platinum-iridium, is preferably used.

The plus electrode321and the minus electrode322are formed in a range of an arc shape corresponding to a predetermined center angle in the outer circumferential surface of the conducting wire sheathing body310substantially having a columnar shape. The magnitude of the center angle for defining the forming range of each of the electrodes321and322may be appropriately set in consideration of the following matter.

If the center angle is excessively small, the area of each of the electrodes321and322is excessively small, and a high voltage for electrostimulation should be applied. If the center angle is excessively large, the area of each of the electrodes321and322is excessively large, and electricity is likely to leak to other peripheral tissues.

For example, when electrical stimulus is applied to a vagus nerve in the vicinity of a superior vena cava, if the center angle is set to be excessively large, electricity may leak and a phrenic nerve which is running near the vagus nerve may be stimulated. If the center angle is excessively large, the electrode and blood are likely to come into contact with each other, and electrical energy flows through blood rather than a vascular tissue facing the vagus nerve, making it difficult to stimulate the vagus nerve.

The dimension of each of the electrodes321and322in the longitudinal direction of the conducting wire sheathing body310and the distance between the plus electrode321and the minus electrode322may be appropriately set. In this embodiment, the dimension of each of the electrodes321and322in the longitudinal direction of the conducting wire sheathing body310is about 2 millimeters (mm), and the distance between the plus electrode321and the minus electrode322is about 5 mm.

The electrode support330is constituted by two superelastic wires331. Each superelastic wire331is formed so as to maintain a frame shape (first shape) with an increasing width in the width direction of the conducting wire sheathing body310in the natural site where no external force is applied, and both end portions of each superelastic wire331are fixed to the conducting wire sheathing body310.

As shown inFIG. 40on a magnified scale, a virtual surface VS which is formed by the electrode support330in the first shape has an arc shape which is made convex toward the electrode portion320when viewed in the axial direction of the conducting wire sheathing body310. The radius of curvature of the arc is set to be a value equal to or greater than the average diameter in which the biological implantable electrode301is placed.

The electrode support330is configured such that the shape thereof can be changed when external force is applied and reversibly returns to the first shape if an external force is eliminated. As the material of the superelastic wire331, nickel-titanium alloy or the like may be used.

If necessary, the outer circumference of the superelastic wire331may be subjected to coating using a polyurethane tube, a tube made of fluorine resin, or the like. When this happens, the slidability of the superelastic wire331can be improved, and accommodation in the withdrawal portion340can be carried out with a small force.

The withdrawal portion340includes a tubular member341through which the conducting wire sheathing body310passes, and an attachment342which fixes the tubular member341to the conducting wire sheathing body310.

The tubular member341has rigidity such that the support330can be deformed, and has an inner diameter greater than the outer diameter of the conducting wire sheathing body310. On the base end side of the tubular member341, screw threads (not shown) are provided to fix the tubular member341to the attachment342.

The attachment342is fixed to the conducting wire sheathing body310, and thread grooves (not shown) which is engageable with the screw threads of the tubular member341are formed in the inner surface on the leading end side of the attachment342.

With the above-described configuration, when the tubular member341is fixed to the attachment342, the tubular member341is held so as not to relatively move in the axial direction thereof with respect to the conducting wire sheathing body310. When the tubular member341is disengaged from the attachment342, the tubular member341can relatively move with respect to the conducting wire sheathing body310.

An operation at the time of the use of the biological implantable electrode301configured as above will be described in connection with an example where the electrode portion320is placed in the superior vena cava.

The operator makes an incision on the cervical region of a patient to expose a jugular vein JV. Next, as shown inFIG. 41, the operator makes an incision on the jugular vein JV and inserts the leading end of an introducer3100into the jugular vein JV. As the introducer3100, a known introducer having a check valve is appropriately selected and used in consideration of an inner diameter or the like such that the biological implantable electrode301smoothly passes therethrough.

Next, the operator manually folds and deforms the electrode support330and inserts the biological implantable electrode301into the introducer3100(second shape deformation process). In the introducer3100, the electrode support330is deformed to a second shape appropriate for introduction into the vein to follow the conducting wire sheathing body310. After the electrode support330entirely enters the introducer3100, the operator moves the conducting wire sheathing body310into the jugular vein JV through the introducer3100. The electrode support330which passes through the introducer3100and protrudes into the jugular vein JV returns to the first shape appropriate for supporting the electrode portion in the biological body (first shape deformation process). The first shape is an arc shape which is made convex toward the electrode portion320. Since the radius of curvature of the arc is equal to or greater than the average diameter of the jugular vein JV, the electrode support330cannot completely return to the first shape, and presses the electrode portion320and the inner wall of the jugular vein JV to urge the electrode portion320to be in close contact with the inner wall.

When the operator further pushes the biological implantable electrode301with constant force, while the electrode support330is sliding on the inner wall of the vein, the biological implantable electrode301goes forward. The operator moves the electrode portion320to a predetermined position of the superior vena cava V1near the vagus nerve while confirming the position of the electrode portion320inside the body of the patient by an X-ray fluoroscopic image or the like.

As shown inFIG. 42, in a state where the base end side of the tubular member341and the attachment342are located outside the jugular vein JV, the operator sutures the jugular vein JV and the cervical region, and ends the placement procedure of the biological implantable electrode301. The introducer3100is withdrawn or torn and removed.

After the biological implantable electrode301is placed, the operator connects the electrical stimulus generation device to the conducting wire sheathing body310and stimulates the vagus nerve beyond the vascular wall of the superior vena cava V1to carry out a desired treatment. While the biological implantable electrode301is being placed, the position of the electrode portion320is suitably maintained by frictional force between the electrode support330in the first shape and the vascular wall.

At the time of the end of the treatment period or the like, in withdrawing the biological implantable electrode301, as shown inFIG. 43, the tubular member341is disengaged from the attachment342. As shown inFIG. 44, the conducting wire sheathing body310is drawn out outside the body while the tubular member341is being fixed. When the electrode support330is drawn and accommodated in the tubular member341, the electrode support330is deformed to the second shape in the tubular member341(second shape re-deformation process). In a state where the electrode support330is accommodated in the tubular member341, the operator extracts the suture thread which has fixed the341, and as shown inFIG. 45, withdraws the biological implantable electrode301from the jugular vein JV. After the biological implantable electrode301is withdrawn, the operator sutures and completely closes the jugular vein JV and the cervical region.

According to the biological implantable electrode301of this embodiment, the electrode support portion330can be reversibly deformed between the first shape appropriate for supporting the electrode portion in the biological body and the second shape appropriate for introduction and withdrawal with respect to the biological body. For this reason, at the time of introduction or withdrawal with respect to the vein or the like, the electrode support portion330is deformed to the second shape and can be moved in and out through a comparatively small incision portion. At the time of the placement, the electrode support portion330is deformed to the first shape, such that the electrode portion320can be supported at a predetermined position of the vein or the like. As a result, the electrode portion can be placed in the biological body with a small amount of invasion without using a thoracoscope, a trocar, or the like, and electrical stimulus can be applied to a target portion beyond adjacent tissues. After the treatment, the electrode support portion is again deformed to the second shape, such that the electrode support portion can be easily withdrawn from the biological body without making a large incision on the incision portion which is formed for introduction.

The virtual surface VS which is formed by the electrode support330has an arc shape which is made convex toward the electrode portion320and has the radius of curvature greater than the average diameter of the vein in which the biological implantable electrode301is placed. Therefore, the electrode portion320can be constantly urged so as to be in close contact with the vascular wall, and an electrostimulation treatment can be satisfactorily carried out.

The withdrawal portion340is provided, such that the electrode support330is changed to the second shape without using an introducer, easily withdrawing the biological implantable electrode301. Since the withdrawal portion340includes the attachment342, the tubular member341can be stably maintained until withdrawal without being relatively moved with respect to the conducting wire sheathing body310.

The withdrawal portion340includes the tubular member341, such that the electrode support330can be stabilized to the second shape only by accommodating the electrode support330in the tubular member341. Thus, when the biological implantable electrode301is withdrawn, the electrode support330returns to the first shape, making it possible to satisfactorily suppress a situation in which stuck blood or the like flies in all directions and making it possible to realize safe use.

Next, a biological implantable electrode according to an eighth embodiment of the present invention will be described with reference toFIGS. 46 to 49. Similarly to the biological implantable electrode of the seventh embodiment, the biological implantable electrode of this embodiment may be used in combination with the electrostimulation system according to each of the first to fourth embodiments of the present invention. A difference between a biological implantable electrode351of this embodiment and the biological implantable electrode301of the seventh embodiment is the structure of the deformation mechanism. In the following description, the same parts as those described above are represented by the same reference numerals, and overlapping description thereof will be omitted.

FIG. 46is a diagram showing the vicinity of the electrode portion320of the biological implantable electrode351. The biological implantable electrode351includes a deformation sheath (deformation mechanism)352, in place of the withdrawal portion340. The deformation sheath352is formed of the same material as the tubular member341but is longer than the tubular member341, and a leading end portion352A thereof is located in the vicinity of the electrode portion320.

A base end portion331A of a superelastic wire331constituting the electrode support330is connected to the leading end352A of the deformation sheath352. Thus, if the deformation sheath352is relatively moved with respect to the conducting wire sheathing body310, similarly, the base end portion331A of the superelastic wire331is relatively moved with respect to the conducting wire sheathing body310.

FIG. 47is a sectional view of the deformation sheath352. O rings353are attached to both ends of the deformation sheath352. The inner diameter of each of the O rings353is the same (or substantially the same) as the outer diameter of the conducting wire sheathing body310. When the conducting wire sheathing body310passes through the deformation sheath352, both ends of the deformation sheath352are maintained watertight, and blood or the like does not enter the lumen. If force is applied in the axial direction of the deformation sheath352, contact is maintained between the deformation sheath352and the conducting wire sheathing body310to an extent such that the deformation sheath352can slide on the conducting wire sheathing body310.

In placing the biological implantable electrode351of the embodiment, the operator moves back the deformation sheath352with respect to the conducting wire sheathing body310. When this happens, as shown inFIG. 48, the base end portion331A of the superelastic wire331is moved back with respect to the conducting wire sheathing body310, and the electrode support330is drawn out in the longitudinal direction of the conducting wire sheathing body310. Finally, as shown inFIG. 49, the electrode support330is deformed to the second shape substantially parallel to the conducting wire sheathing body310. The operator inserts the electrode support330in the second shape into the introducer3100. The timing at which the electrode support330is inserted into the introducer3100should not be when the electrode support330is completely deformed to the second shape, and may be appropriately adjusted.

Although the flow in which the electrode support330protrudes from the3100and is completely placed is the same as in the first embodiment, in the biological implantable electrode351, the positional relationship between the deformation sheath352and the conducting wire sheathing body310is maintained, maintaining the electrode support330in the second shape even in the vein. For this reason, in a state where the electrode support is in the second shape, the electrode portion320can be moved to the placement portion.

In withdrawing the biological implantable electrode351, similarly to the insertion, the deformation sheath352is moved back to deform the electrode support330to the second shape. The electrode support330which is deformed to the second shape can be easily withdrawn even through a small incision portion.

In the biological implantable electrode351of this embodiment, similarly to the biological implantable electrode301of the seventh embodiment, placement and withdrawal can be easily carried out with respect to the biological body with a small amount of invasion.

Since the deformation sheath352is provided, and the base end portion331A of the superelastic wire331is connected to the deformation sheath, when the deformation sheath352is relatively moved with respect to the conducting wire sheathing body310, it is possible to easily switch the electrode support between the first shape and the second shape. Thus, the electrode support can be smoothly inserted into an introducer or the like and can be maintained in the second shape in the vein or the like. As a result, it is possible to reduce damage to the inner wall or the like of the vein, realizing a biological implantable electrode with a smaller amount of invasion.

Since the O rings353are attached to both ends of the deformation sheath352, both end portions of the deformation sheath352through which the conducting wire sheathing body310passes are maintained watertight. Therefore, it is possible to prevent blood or the like from leaking outside the body through the lumen of the deformation sheath352or flying in all directions, and making it possible to realize safe use.

From the viewpoint of stable motion of the conducting wire sheathing body, the O rings353are preferably at both ends of the deformation sheath352. However, if watertightness is maintained at least at one place of the lumen of the deformation sheath352, leakage of blood or the like is prevented. Thus, an O ring is preferably provided at least at one place, and the arrangement portion may not be the end portion.

Next, a biological implantable electrode according to a ninth embodiment of the present invention will be described with reference toFIGS. 50 to 54. Similarly to the biological implantable electrode of the seventh embodiment and the biological implantable electrode of the eighth embodiment, the biological implantable electrode of this embodiment may be used in combination with the electrostimulation system according to each of the first to fourth embodiments of the present invention. A difference between a biological implantable electrode361of this embodiment and the biological implantable electrode of each of the foregoing embodiments is in that the biological implantable electrode itself does not include a deformation mechanism.

FIG. 50is a diagram showing the vicinity of the electrode portion320of the biological implantable electrode361on a magnified scale. Similarly to the biological implantable electrode301of the seventh embodiment, the biological implantable electrode361includes the conducting wire sheathing body310, the electrode portion320, and the electrode support330, and is different from the biological implantable electrode301in that the withdrawal portion340is not provided.

In placing the biological implantable electrode361, as in the seventh embodiment, the electrode support330is deformed and inserted into the introducer3100.

In withdrawing the biological implantable electrode361, two towing tools (deformation mechanism)362shown inFIG. 50are inserted into the vein. Each of the towing tools362includes a linear portion363which is constituted by a wire or the like having predetermined rigidity and a locking portion364which is provided at the leading end of the linear portion363. The operator moves forward the towing tools362and locks the locking portion364of each towing tool362to the base end side of each superelastic wire331of the electrode support330while confirming using an X-ray fluoroscopic image.

After it is confirmed that the locking portions364are locked to the superelastic wires331, the operator tows so as to move back the linear portions363. When this happens, as shown inFIG. 51, the electrode support330is towed by the towing tools362, is gradually deformed, and as shown inFIG. 52, is deformed to the second shape. Thereafter, the biological implantable electrode361is withdrawn in the same procedure as in the eighth embodiment.

In the biological implantable electrode361of the embodiment, similarly to the biological implantable electrode of each of the seventh and eighth embodiments, placement and withdrawal can be easily carried out with respect to the biological body with a small amount of invasion.

Since the towing tools362serving as a deformation mechanism is provided separately from the biological implantable electrode361, the biological implantable electrode itself can be reduced in diameter, and can be placed in the body through a smaller incision portion.

Although in this embodiment, an example has been described where, at the time of withdrawal, the two towing tools362are used, as in a modification shown inFIG. 53, a single towing tool362may be used to deform the electrode support.

In a biological implantable electrode361ashown inFIG. 53, an auxiliary wire365is attached at a position most distant from the conducting wire sheathing body310on the base end side of each superelastic wire331of the electrode support330. The base end side of each auxiliary wire365is connected to a movable member366which is slidably attached to the conducting wire sheathing body310.

In withdrawing the biological implantable electrode361a, the operator locks the locking portion364of the towing tool362to the movable member366or the auxiliary wire365in the vicinity of the movable member366and carries out towing. The movable member366towed by the towing tool362slides to the base end side along the conducting wire sheathing body310. As a result, as shown inFIG. 54, the electrode support330is deformed, and finally, as shown inFIG. 55, the electrode support330is deformed to the second shape.

In the biological implantable electrode361aof this modification, withdrawal can be carried out using a single towing tool, such that an operation at the time of withdrawal is more facilitated. The movable member366to which the locking portion364of the towing tool362is locked has the maximum dimension in the width direction greater than the superelastic wire331or the auxiliary wire365, and is easily confirmed under an X-ray fluoroscope or the like.

In this modification, the movable member366may be provided distant from the conducting wire sheathing body310. While the movable member366is not provided, both ends of a single auxiliary wire365may be connected to the superelastic wires331. Even in this case, similarly, the towing tool362or the like is locked to the auxiliary wire365, such that the electrode support330can be deformed.

Next, a biological implantable electrode according to a tenth embodiment of the present invention will be described with reference toFIGS. 56 to 58. Similarly to the biological implantable electrode of the seventh embodiment, the biological implantable electrode of the eighth embodiment, and the biological implantable electrode of the ninth embodiment, the biological implantable electrode of this embodiment may be used in combination with the electrostimulation system according to each of the first to fourth embodiments of the present invention. A difference between a biological implantable electrode371of this embodiment and the biological implantable electrode of each of the foregoing embodiments is a structure to deform the electrode support330.

FIG. 56is a diagram showing the vicinity of the electrode portion320of the biological implantable electrode371in partial sectional view. Although the basic structure of the conducting wire sheathing body372is the same as the above-described conducting wire sheathing body310, in this embodiment, for ease of understanding of the internal structure, the dimension in the radial direction is magnified.

The base end side of each superelastic wire331of the electrode support330is inserted into a space between the insulating layer311and the conducting wire312inside the conducting wire sheathing body372, and protrudes from the base end side of the conducting wire sheathing body372through the conducting wire sheathing body372.

In deforming the electrode support330to the second shape, the base end side of each superelastic wire331is towed. When this happens, as shown inFIG. 57, the superelastic wire331is drawn and deformed in the conducting wire sheathing body372. Finally, as shown inFIG. 58, the electrode support330is deformed to the second shape according to the conducting wire sheathing body372.

In the biological implantable electrode371of this embodiment, similarly to the biological implantable electrode of each of the foregoing embodiments, placement and withdrawal can be easily carried out with respect to the biological body with a small amount of invasion.

The electrode support330can be deformed by operating the base end sides of the superelastic wires331protruding from the base end side of the conducting wire sheathing body372. Thus, complex preparation working is not required before the electrode support330is deformed, and the shape of the electrode support can be easily switched.

The embodiments of the invention have been described, the technical scope of the invention is not limited to the embodiments, the combination of the constituent elements of each embodiment may be changed or the respective constituent elements may be changed or eliminated without departing from the spirit and scope of the invention.

For example, although in the foregoing embodiments, an example has been described where an electrode support is formed by two superelastic wires, one superelastic wire may be used to form the above-described virtual surface VS, thereby constituting an electrode support.

Next, an electrostimulation system according to an eleventh embodiment of the present invention will be described with reference toFIGS. 59 to 69. The electrostimulation system is placed in a vein of a patient for a certain period and used to apply an electrical stimulus to a nervous tissue around the vein through a tube wall of the vein.

As shown inFIGS. 59 and 60, an electrostimulation system401of the embodiment includes an electrode unit402configured to place a leading end portion into the vein, and an electrostimulation device (a stimulus generating unit)420and a syringe piston pump (a liquid medicine supply unit)425detachably attached to the electrode unit402and installed at the outside of the body.

The electrode unit402includes a leading end attachment431and a base end attachment432disposed to be spaced apart from each other, four wire portions (support portions)433having end portions connected to the leading end attachment431and the base end attachment432, a pair of stimulation electrodes434installed at one of the four wire portions433, an interconnection portion435having a leading end portion electrically connected to the stimulation electrodes434, and a liquid feed tube436disposed to extend along the interconnection portion435.

In this embodiment, the attachments431and432are formed of a material having biocompatibility such as stainless steel, titanium, or the like, in a substantially columnar shape. The leading end attachment431is disposed at a position closer the leading end side than the base end attachment432.

As shown inFIG. 61, the wire portion433has a wire441installed at a center thereof, an inner capsule442configured to cover an outer circumferential surface of the wire441, and an outer capsule443configured to cover the outer circumferential surface of the inner capsule442.

The wire441may be formed by appropriately using a material, for example, a shape memory alloy, a superelastic wire, or the like, which returns to its original shape without plastic deformation when the external force is released after an external force is applied to the wire441in a natural state in which no external force except for gravity is applied. An outer diameter of the wire441is set to, for example, φ0.2 to 0.5 mm.

The capsules442and443are formed of a resin such as polyurethane or the like and have a thickness of 50 to 500 μm. According to the above-mentioned configuration, the outer circumferential surface of the outer capsule443becomes smooth, and generation of thrombus on the outer circumferential surface is prevented.

When a linear axis C1(seeFIG. 59) passing through the leading end attachment431and the base end attachment432is defined, a pair of through holes443aare formed parallel to an axis C1direction in the outer capsule443at an opposite side of the axis C1of an intermediate portion in the axis C1direction of the outer capsule443. When seen from a side view ofFIG. 62, the through holes443aare formed in a substantially oval shape, which is long in the axis C1direction. A size of the through hole443ahas, for example, a major axis of 1.8 mm and a minor axis of 0.5 mm. A distance in the axis C1direction of a center portion of the pair of through holes443ais set to about 3 to 5 mm.

As shown inFIG. 61, the above-mentioned stimulation electrode434having a cylindrical shape is installed between the inner capsule442and the outer capsule443. The stimulation electrode434has, for example, an outer diameter of about 1 mm and a length of about 2 mm, and is formed of a platinum-iridium alloy or the like. The pair of stimulation electrodes434are installed at the wire portion433. The inner capsule442is inserted into the stimulation electrode434, and the stimulation electrode434, which functions to cover the through hole443a, is exposed to the outside.

An electrical interconnection435aconstituting the interconnection portion435is electrically connected to an inner circumferential surface of the stimulation electrode434. An interconnection in which a stranded wire formed of a nickel-cobalt alloy (35NLT material) having flex resistance is coated with an electrical insulating material (for example, ETFE (polytetrafluoroethylene) of a thickness of 20 μm, or the like) can be appropriately used as the electrical interconnection435a.

The electrical interconnection435ais disposed in the outer capsule443to extend along the outer capsule443, and passes through the base end attachment432to further extend to the base end side.

As shown inFIGS. 59 and 60, the wire portion433is formed of an elastic material and has an arcuate shape, a central angle of which is about 180° as a whole. A radius of the wire portion433is set to about 10 to 20 mm according to an inner diameter of the placed vein.

In this embodiment, the four wire portions433are disposed about the axis C1at the same angle. That is, the wire portions433are disposed such that the intermediate portions in the axis C1direction are curved to be spaced apart from the axis C1and the intermediate portions are spaced part from each other about the axis C1. The four wire portions433are disposed on a spherical surface.

The four wire portions433and the attachments431and432constitute an electrode portion438.

An outer diameter D1of the electrode portion438in a natural state is about 20 to 40 mm. The outer diameter D1is set to be larger than the inner diameter of the vein in which the electrode portion438is placed.

The wire portion33is joined with the attachment31and32through welding, bonding, caulking, or the like.

As shown inFIGS. 59 and 63, a leading end portion of the liquid feed tube36passes through the base end attachment432. The liquid feed tube436has an opening436ain front of the base end attachment432. The opening436ais disposed on the axis C1. A cross section of an inner surface of a pipeline436bof the liquid feed tube436perpendicular to the axis C1has a circular shape. The liquid feed tube436may be formed of a resin, for example, ETFE, or the like.

A leading end portion of a tubular lead main body445is attached to the base end attachment432. A portion of the lead main body445corresponding to a length placed in the vein (a length of about 40 to 200 mm from the base end attachment432) is formed of a flexible material, for example, silicon having a hardness of about A50°, and a base end side from the end portion is formed of a hard material, for example, polyurethane having a hardness of about D60°. Upon placement of the electrode, while a lead manipulation by an operator from the outside of the body is needed, a portion manipulated by the operator may be formed of a hard material such that a stimulation electrode is easily guided to a desired position. In addition, as a flexible material is used for the portion corresponding to the inside of the vein, movement of a position of the stimulation electrode due to a body motion can be prevented. A lead has, for example, an outer diameter of about 2 to 3 mm and a length of about 500 mm.

The above-mentioned interconnection portion435and the liquid feed tube436are inserted into the lead main body445. The base end side of the liquid feed tube436is configured to protrude from a side surface of the lead main body445, and a connector446including a Luer lock is attached to the base end portion of the liquid feed tube436. A portion of the lead main body445, from which the liquid feed tube436protrudes, is a portion positioned at the outside of the body of the patient when the electrode portion438is placed in the vein.

For example, a known IS1 type connector448installed at the base end portion of the lead main body445, and the base end portion of the interconnection portion435is electrically connected to the connector448.

The connector448includes a connector pin448afor a negative electrode and a connector pin448bfor a positive electrode, and a pair of rubber rings448c. The rubber rings448cinsulate the connector pin448afor the negative electrode and the connector pin448bfor the positive electrode from each other, and remain watertight upon connection to the electrostimulation device420. Both of the connector pin448afor the negative electrode and the connector pin448bfor the positive electrode are formed of stainless steel. In addition, the rubber rings448care formed of silicon rubber having biocompatibility. A waterproof connector can be used as the connector448when the electrostimulation device420is installed at the outside of the body, in addition to the IS1 type.

A sheath for withdrawal having a length of 3 to 5 cm is installed at the outside of the lead main body445. The sheath for withdrawal is slidable with respect to the lead main body in the axial direction. In the sheath for withdrawal, an end surface in a leading end portion direction has an acute tapered shape, an end surface in a base end portion direction has a flange shape, and an O-ring is installed in the flange to prevent exposure of blood. Hard polyethylene or polyurethane is appropriate for a material of the sheath.

The electrostimulation device420has an electrical stimulus supply unit (not shown), and can generate an electrical stimulus according to a constant current type or a constant voltage type. In this embodiment, as an electrical stimulus, as shown inFIG. 64, biphasic waveform groups of the constant voltage type having a changing phase are generated at predetermined time intervals. As an example of a specific biphasic waveform, for example, a voltage can be exemplarily varied between plus several volts to minus several volts at a frequency of 20 Hz and a pulse width of 50 to 400 μsec. The electrostimulation device420generates the biphasic waveform for 3 to 10 seconds per minute. In addition, in the case of arrhythmia treatment, the biphasic waveform may be continuously generated.

As shown inFIG. 59, the electrostimulation device420is detachably configured at the base end portion of the interconnection portion435by a connector421included in the electrostimulation device420and the above-mentioned the connector448. Then, when both of the connectors421and448are connected, the electrostimulation device420can apply the above-mentioned biphasic waveform between the pair of stimulation electrodes434installed at the wire portions433. Here, one stimulation electrode434of the pair of stimulation electrodes434acts as a plus-side electrode, and the other stimulation electrode434acts as a minus-side electrode.

The syringe piston pump425has a known configuration, and a piston427is slidable with respect to a syringe426. An inlet port426aformed at a leading end portion of the syringe426is detachable and attachable with respect to the connector446of the liquid feed tube436. An anticoagulant agent such as heparin, argatroban, or the like, or a diluted solution thereof is accommodated in the syringe426, and as the piston427is pushed into the syringe426in a state in which the inlet port426ais mounted on the connector446, the anticoagulant agent can be supplied into the pipeline436bof the liquid feed tube436through the inlet port426a.

Next, a procedure of placing the electrode portion438of the electrode unit402into the superior vena cava will be described using the electrostimulation system401configured as above. In this case, an outer diameter D1in a natural state of the electrode portion438is set to be larger than the inner diameter of the superior vena cava. In the electrostimulation system401to be described below, in an initial state, the electrostimulation device420and the syringe piston pump425are not mounted.

In addition, the electrostimulation system401is appropriate to perform a temporary nerve stimulus for a short amount of time, unlike a long-term nerve stimulation system in which the entire system is implanted in the body.

First, as shown inFIG. 65, the operator performs a small incision of the skin in the vicinity of the right of the neck of a patient P, and forms an opening P1. The electrode portion438of the electrode unit402is firstly introduced into the external jugular vein P2or the internal jugular vein P4via a known introducer or a dilator (not shown) from the opening P1. In this case, as a position of the wire441or the interconnection portion435of the wire portion433is checked under an X-ray, the electrode portion438of the electrode unit402is introduced while checking a position of the electrode unit402. In addition, the insertion position is not limited thereto but insertion from the left of the neck, the right subclavian vein or the left subclavian vein may also be performed.

When the electrode portion438is introduced into the external jugular vein P2, as shown inFIG. 66, the respective wire portions433are elastically deformed to the axis C1side and reduced in diameter throughout the electrode portion438as they are pushed into the inner wall of the external jugular vein P2, and extend in the axis C1direction. Accordingly, an outer diameter D2of the electrode portion438is smaller than the outer diameter D1in the natural state.

The operator introduces the electrode unit402while checking the position under the X-ray, and as shown inFIG. 67, the electrode portion438is roughly disposed at the superior vena cava V1. Even in this case, since the outer diameter D1of the electrode portion438is set as described above, the wire portions433are pushed to the axis C1side by the superior vena cava V1, and as shown inFIG. 61, the stimulation electrodes434exposed from the through hole443aare disposed to oppose the inner wall of the superior vena cava V1.

As shown inFIG. 67, a vagus nerve (a nervous tissue) VN and a cardiac branch of the vagus nerve P7near the superior vena cava V1keep pace in parallel with each other.

Next, in the outside of the body of the patient P, the connector448of the interconnection portion435and the connector421of the electrostimulation device420are connected to each other, and a biphasic waveform group is generated from the electrostimulation device420to be applied between the pair of stimulation electrodes434.

The operator manipulates the lead main body445and adjusts a position in a longitudinal direction of the superior vena cava V1in the electrode portion438, and measures a heart rate by an electrocardiograph or the like attached to the patient P while rotating the lead main body445about the axis C1. When the pair of stimulation electrodes434are disposed to approach and oppose the vagus nerve VN or the cardiac branch of the vagus nerve P7and an electrical stimulus transmitted to the vagus nerve VN or the cardiac branch of the vagus nerve P7from the pair of stimulation electrodes434is increased, the heart rate of the patient P is extremely decreased. The operator adjusts a direction about the axis C1of the electrode portion438to extremely decrease the heart rate, i.e., such that the pair of stimulation electrodes434are directed to the side of the vagus nerve VN or the cardiac branch of the vagus nerve P7.

In a state in which the position about the axis C1of the electrode portion438is determined, the electrode unit402is placed in the superior vena cava V1.

Then after the introducer or the dilator is removed, the sheath for withdrawal enters the position P1at which the small incision is performed, and the incised portion is sutured in a state in which a portion of the sheath for withdrawal enters the vein. Since an O-ring is installed in the sheath for withdrawal, the blood is not exposed to the outside of the body.

Outside of the body of the patient P, when the inlet port426aof the syringe piston pump425is connected to the connector446of the liquid feed tube436to slowly push the piston427, the anticoagulant agent or a diluted solution thereof passes through the pipeline436bof the liquid feed tube436to be discharged into the blood from the opening436a. A discharge speed of the anticoagulant agent or the diluted solution thereof is, for example, about 0.05 to 40 ml per hour. The anticoagulant agent is continuously discharged while the electrode portion438is placed.

In an area of the superior vena cava V1in which the electrode portion438is disposed, the blood flows as shown by an arrow A1ofFIG. 67. Since a blood flow stagnates in the vicinity of the leading end attachment and the vicinity of the base end attachment, the thrombus is likely to be generated in these areas. As a liquid including an anticoagulant agent is continuously discharged from the opening436a, stagnation of the blood flow in the vicinity of the leading end attachment and the vicinity of the attachment is prevented, the anticoagulant agent is present in the vicinity of the wire and the attachment at a high concentration, and solidification of the blood and generation of the thrombus at the wire portion433or the attachments431and432is suppressed.

In addition, a time for starting supply of the anticoagulant agent is not limited thereto but may be appropriately set such that supply of the anticoagulant agent is started when the electrode portion438is disposed in the superior vena cava V1.

When an electrical stimulus is continuously applied to the vagus nerve VN for a certain period by the electrostimulation device420, the electrostimulation device420and the syringe piston pump425are removed from the electrode unit402.

When the electrode unit402is pulled back into the sheath for withdrawal, since the outer diameter of the electrode portion438is varied according to the inner diameter of the sheath for withdrawal, the electrode unit402can be removed even from a small wound to be easily extracted to the outside of the body of the patient P. There is no need for a re-operation with a large surgical invasion for removal of the electrode unit402.

After that, an appropriate treatment such as suturing of the opening P1is performed, and a series of procedures are completed.

As described above, according to the electrode unit402and the electrostimulation system401of the embodiment, the electrode portion438is disposed in the superior vena cava V1having an inner diameter smaller than the outer diameter D1of the electrode portion438in the natural state. Here, in a state in which the stimulation electrode434side of each of the wire portions433abuts the inner wall of the superior vena cava V1, the wire portion433is elastically varied to the axis C1side and extends in the axis C1direction. Accordingly, the stimulation electrode434can come in secure contact with the inner wall of the superior vena cava V1.

The biphasic waveform group generated by the electrostimulation device420is applied between the pair of stimulation electrodes434via the interconnection portion435, and the electrode unit402is rotated about the axis C1to measure the heart rate of the patient P. As a result, a direction of the electrode portion438can be adjusted such that the stimulation electrode434can be directed to the vagus nerve VN side to effectively apply the electrical stimulus to the vagus nerve VN. The stimulation electrode434can be suppressed from coming in contact with the blood, and the voltage applied between the pair of stimulation electrodes434can be suppressed from being leaked to the blood side.

As the anticoagulant agent supplied from the syringe piston pump425is discharged into the blood from the opening436athrough the liquid feed tube436, solidification of the blood and generation of the thrombus at the wire portion433or the attachments431and432can be suppressed. Since the thrombus is likely to be generated at an area at which interference with the blood flow is likely to occur, a discharge port of the anticoagulant agent can be actively and effectively formed at a place at which the attachments431and432and the wire portion433are collected.

As described above, as the electrical stimulus is applied to the vagus nerve VN via the tube wall of the superior vena cava V1from the pair of stimulation electrodes434disposed in the superior vena cava V1, the electrical stimulus can be indirectly applied with no direct contact with the vagus nerve VN. Accordingly, minimally invasive treatment can be performed.

The wire portions433are disposed about the axis C1at the same angular intervals. For this reason, four wire portions433are disposed in a four-fold rotationally symmetrical shape with respect to the axis C1. For this reason, even when the electrode portion438is rotated about the axis C1, variation in the shape is reduced, and manipulation performance of the electrode portion438is improved.

While the vein in the living body has various shapes according to the areas, since the wire portions433of the embodiment are disposed about the axis C1at the same angular intervals, the wire portions433are deformed according to various vein shapes, and the stimulation electrode434securely abuts the inner wall of the vein, suppressing a leakage of electricity to the blood.

In addition, although the effect is decreased, even when the wire portions433are disposed about the axis C1at irregular angles, it is needless to say that manipulation performance of the electrode portion438can be somewhat improved and the wire portions433can correspond to the shape of the vein.

Further, in the embodiment, while the four wire portions433are provided, it is needless to say that the electrode portion438can be fixed to an appropriate position in the vein as long as the number of wire portions433is two or more. As the number of wire portions433is increased, more stable manipulation performance can be realized, and fixing according to various vein shapes can be easily realized.

In recent times, in a field of treatment of heart failure, it has been known that, as an electrostimulation system of directly applying electronic intervention with respect to an autonomic nerve is used, abnormal circulation adjustment can be corrected and life prognosis of the patient can be improved.

In addition, in an acute myocardial infarction patient's condition, as vagus nerve stimulation treatment for several days after outbreak of an illness is performed using the electrostimulation system, arrhythmias generated according to reperfusion treatment and arrhythmia and heart remodeling generated after myocardial infarction can be reduced. It is already known that the vagus nerve stimulus suppresses generation of the arrhythmia according to the arrhythmia or reperfusion treatment after the myocardial infarction. The vagus nerve stimulus having an appropriate strength reduces a cardiac load via an increase in heart rate and an increase in peripheral vascular resistance to protect the myocardium by a centrifugal nerve stimulus effect and a centripetal nerve stimulus effect thereof, and reduces a myocardial infarction region (the myocardium amount necrosed by the myocardial infarction). In addition, acetylcholine discharged from a nerve ending to the heart by the centrifugal vagus nerve stimulus has an anti-inflammatory action and an anti-apoptotic effect, and directly protects the myocardial cell, and the vagus nerve stimulus suppresses the heart remodeling after the myocardial infarction and prevents progress of the heart failure via these plurality of mechanisms.

The vagus nerve stimulation can be performed at various areas along its length, and in general, vagus nerve stimulation at the cervix is performed. However, since the vagus nerve governs not only the heart but also various internal organs, the vagus nerve stimulus in an area near the center exerts an influence on many internal organs. In order to prevent generation of side effects due to stimulation of the vagus nerve governing internal organs other than a target internal organ, vagus nerve stimulation at an area nearer the target internal organ is preferable. When the vagus nerve stimulation is performed at the area nearer the heart, since it is not necessary to worry about side effects to the other internal organs, stimulation can be performed at a strength enabling accomplishment of substantial effects with respect to the heart. As the chest vagus nerve near the superior vena cava is stimulated, a recurrent laryngeal nerve stimulus generated by the cervix vagus nerve stimulus can be avoided, and side effects such as hoarseness can be prevented. Further, as only the cardiac branch of the vagus nerve near the superior vena cava is stimulated, stimulation of the vagus nerve governing the alimentary canal can be avoided, and side effects such as diarrhea, rumbling stomach, or the like can be prevented. Furthermore, a large amount of skeletal muscles are present around the vagus nerve in the cervix, and these muscles are stimulated by a leakage current upon nerve stimulation to cause symptoms such as twitching or pains. The vagus nerve near the superior vena cava is not surrounded by the skeletal muscle, and symptoms such as twitching or pains do not easily occur.

According to the electrostimulation system401of the embodiment, when the electrical stimulation is performed on the nervous tissue, desired nerve stimulation can be realized without large surgical invasion to the nervous tissue, which is a target. Installation of the electrode unit402can be realized by a general transvenous approach widely used in a catheter operation, and in order to apply an indirect electrical stimulus without direct contact with a nerve, the installation can be completed for a short time to remove the electrode unit402after completion of treatment, without worrying about damage to the nervous tissue upon installation of the electrode unit402. Accordingly, the electrode unit402is appropriate for the case of a temporary nerve stimulation treatment or upon emergency requiring a treatment start for a short time, realizing minimally invasive treatment with respect to the patient.

In addition, in this embodiment, like an electrode unit402A as shown inFIG. 68, a side opening436cin communication with the pipeline436bof the liquid feed tube436may be formed in an intermediate portion in the longitudinal direction of the liquid feed tube436, and the side opening436cmay be exposed to the outside from the lead main body445. A position at which the side opening436cis formed may be disposed in the vein when the electrode unit402A is introduced into the body.

According to the above-mentioned configuration, when the anticoagulant agent is supplied from the syringe piston pump425, the anticoagulant agent is discharged even from the side opening436c. Accordingly, generation of the thrombus in the wire portion433or the attachments431and432can be more securely suppressed.

In addition, it is needless to say that the number of side openings436cformed in the liquid feed tube436is not limited thereto but may be plural.

Further, in this embodiment, like an electrode unit4100A as shown inFIG. 69, an opening436gmay be formed at the base end side (a side directed inward in the basket) of the leading end attachment431.

The liquid feed tube436extends from the base end attachment432, and is connected to the leading end attachment431by a liquid feed tube4101along the axis C of the wire portion433to the leading end attachment431. A flow path inserted into the opening436gformed in the base end side (a side directed inward in the basket) is formed in the leading end attachment431.

In recent times, a medical antithrombotic coating agent having heparin as a base or a hydrophilic medical antithrombotic coating agent is used, and even in the embodiment, generation of the thrombus can be reduced by treating a lead surface, the wire portion433, or surfaces of the attachments431and432with the coating agent. However, since the vicinity of the leading end attachment431, which is most likely to interfere with the blood flow, has a structure in which the plurality of wire portions433are concentrated, it is difficult to completely prevent generation of the thrombus using only the medical antithrombotic coating agent. For this reason, the opening436gconfigured to discharge the anticoagulant agent is formed at a surface side opposite to the blood flow of the leading end attachment431(a side directed inward in the basket), and the discharged anticoagulant agent stagnates in the vicinity of the leading end attachment431in a relatively high concentration state, more effectively preventing generation of the thrombus. In addition, since the anticoagulant agent flows along an external shape of the leading end attachment431by relatively increasing the discharged amount, adherence of the thrombus can also be further suppressed by the action of the flow.

Like the embodiment, when the vagus nerve near the superior vena cava or the cardiac branch of the vagus nerve is stimulated, the electrostimulation system should be placed in the superior vena cava. Here, since the superior vena cava is the vein directly connected to the heart, a large flow rate of blood intermittently flows. For this reason, different from the internal jugular vein through which a relatively small flow rate of blood continuously flows, a larger thrombus is easily formed in the superior vena cava. In this point, according to the electrostimulation system of the present invention, when placed in the superior vena cava, as the anticoagulant agent or the diluted solution thereof is discharged, formation of the thrombus can be appropriately prevented. For this reason, unlike the conventional electrostimulation system that should be placed in the internal jugular vein in which a large thrombus cannot be easily formed, the electrostimulation system according to the embodiment can be safely placed in the superior vena cava, and can more effectively apply the electrical stimulus to the vagus nerve or the cardiac branch of the vagus nerve.

Next, while a twelfth embodiment of the present invention will be described with reference toFIGS. 70 to 74, like elements in the embodiment are designated by like reference numerals, description thereof will be omitted, and only differences will be described.

As shown inFIGS. 70 and 71, an electrode unit404used in an electrostimulation system403of the embodiment has a position of the opening436aof the liquid feed tube436varied in the electrode unit402of the eleventh embodiment, and includes a guide sheath450.

In this embodiment, a leading end side of a liquid feed tube456is attached to a surface of the axis C1side of one wire portion433. An opening456aof a leading end side of the liquid feed tube456is disposed to oppose side surfaces of the leading end attachment431.

A curved portion451curved in a natural state is installed at the leading end portion of the guide sheath450. The curved portion451has a central angle set to about 45 to 90° to be easily directed to the internal jugular vein side (to be described later). An inner diameter of a channel452of the guide sheath450is set such that the electrode portion438having a reduced diameter can be inserted thereinto.

The guide sheath450can be formed of ETFE or the like as described above, and a thickness thereof is set such that the operator can easily tear the guide sheath450in a circumferential direction thereof. A groove extending in a longitudinal direction may be formed at an outer surface of the guide sheath450such that the guide sheath450is easily torn.

Next, a procedure of placing the electrode portion438in the internal jugular vein using the electrostimulation system403having the above-mentioned configuration will be described. In this case, the outer diameter D1in the natural state of the electrode portion438is set to be larger than the inner diameter of the internal jugular vein. As shown inFIG. 72, the vagus nerves VN keep pace in parallel in the internal jugular vein P4.

The electrode unit404on which the guide sheath450is mounted is transvenously introduced through the right external jugular vein P2from the opening P1. Alternatively, the opening P1of the skin may be formed in the vicinity of the right clavicle, and may be transvenously introduced through the right subclavian vein P7. Since the curved portion451is installed at the leading end side of the guide sheath450, the electrode portion438introduced into the right subclavian vein P7can be directed to the internal jugular vein P4side. The electrode unit404is pushed to place the electrode portion438in the internal jugular vein P4, and then the guide sheath450is torn and removed.

After that, similar to the eleventh embodiment, a direction about the axis C1of the electrode portion438is adjusted. Even in the embodiment, as the pair of stimulation electrodes434face each other at the vagus nerve VN side to abut the vein inner wall, the heart rate of the patient P is remarkably reduced.

Continuously, when the syringe piston pump425is connected to the liquid feed tube456to push the piston427, the anticoagulant agent is discharged into the blood from the opening456aof the liquid feed tube456. As shown by an arrow A2ofFIG. 72, the blood flows in the area at which the electrode portion438is disposed in the internal jugular vein P4. For this reason, the anticoagulant agent discharged from the opening456amoves to the base end attachment432with the blood along the wire portion433, and solidification of the blood and generation of the thrombus at the wire portion433or the attachments431and432are suppressed.

As described above, according to the electrode unit404and the electrostimulation system403of the embodiment, even when the electrode portion438is placed in the internal jugular vein P4, the electrical stimulus can be indirectly applied with no direct contact with the vagus nerve VN.

As the guide sheath450is included in the electrode unit404, the electrode portion438introduced into the right subclavian vein P7can be easily directed to the internal jugular vein P4side, and the procedure can be easily performed.

In addition, it is needless to say that generation of the thrombus can be more effectively suppressed by further forming an opening near the base end attachment432to discharge the anticoagulant agent.

Further, in this embodiment, like the electrode unit404A as shown inFIGS. 73 and 74, an opening portion431aopened at the leading end side is formed in the leading end attachment431, and the opening456aof the liquid feed tube456may be configured to be in communication with the opening portion431a.

As the electrode unit404A is configured as described above, when the electrode unit404A is placed in the internal jugular vein P4, the anticoagulant agent can be discharged from the opening portion431a. Accordingly, the thrombus generated at a connecting portion between the leading end attachment431and the wire portion433can also be effectively reduced.

In addition, the opening configured to discharge the anticoagulant agent is not limited thereto but may have, for example, the opening portion configured to open the base end attachment432side.

While also described in the eleventh embodiment, a place at which the thrombus is easily generated is positioned inside the attachment near the heart (downstream of the blood flow). Here, since structure members are concentrated, the blood flow is delayed to easily generate the thrombus. While formation of the thrombus is related to the blood flow, a contact with a device, and an element of the blood, generation of the thrombus can be prevented by preventing stagnation of the blood through formation of an active flow in an area at which the thrombus is easily generated (improvement of the blood flow) or administering an anticoagulant to the area at which the thrombus is easily generated at a high concentration (improvement of the blood elements).

Accordingly, similar to the configuration shown inFIG. 59, as the liquid including the anticoagulant agent is continuously discharged from the opening436aformed at the base end attachment432side, a flow prevented by stagnation of the blood flow is formed in the vicinity of the base end attachment, and the anticoagulant agent acts at a high concentration.

As described above, according to the blood flow of the vein in which the electrode portion is installed, as the opening configured to actively discharge the anticoagulant agent is formed at the area at which the thrombus is easily generated, generation of the thrombus can be effectively suppressed.

Next, while a thirteenth embodiment of the present invention will be described with reference toFIGS. 75 to 78, like elements in the embodiment are designated by like reference numerals, description thereof will be omitted, and only differences will be described.

As shown inFIG. 75, an electrode unit406used in an electrostimulation system405of the embodiment includes, in addition to the components of the electrode unit402of the eleventh embodiment, a pair of measurement electrodes461installed at the wire portion433different from the wire portion433at which the pair of stimulation electrodes434are installed, and a second interconnection portion462having a leading end portion electrically connected to the pair of measurement electrodes461.

As shown inFIGS. 76 and 77, in the outer capsule443, a pair of through holes443bare formed in parallel in the axis C1direction at the axis C1side of the intermediate portion in the axis C1direction at an interval of 5 to 10 mm. The through holes443bhave a substantially rectangular shape, which is long in the axis C1direction, when seen from a side view. The through hole443bhas, for example, a long side of 1.8 mm and a short side of 0.8 mm, which is larger than the through hole443a.

As shown inFIG. 76, the measurement electrode461has a cylindrical shape and is disposed to be shifted in the axis C1direction from the stimulation electrode434. The measurement electrode461covers the through hole443band is exposed to the outside. An electrical interconnection462aconstituting the second interconnection portion462is electrically connected to the inner circumferential surface of the measurement electrode461. Since the measurement electrode461and the second interconnection portion462have the same configurations as the stimulation electrode434and the interconnection portion435, description thereof will be omitted.

As shown inFIG. 75, a lead main body464is branched into a first branch portion465and a second branch portion466in the base end side. The above-mentioned connector448is installed at the base end portion of the first branch portion465, and the base end portion of the interconnection portion435is electrically connected to the connector448. A connector468having the same shape as the connector448is installed at the base end portion of the second branch portion466, and the base end portion of the second interconnection portion462is electrically connected to the connector468. That is, in the embodiment, the electrode unit406is branched into three, i.e., the liquid feed tube436, the first branch portion465and the second branch portion466in the base end side. The first branch portion465becomes an electrical stimulation lead, and the second branch portion466becomes a sensing lead.

While not shown, the electrostimulation device of the embodiment is detachable from both of the connectors448and468. The electrostimulation device of the embodiment includes, in addition to the respective components of the electrostimulation device420, a heart rate measurement unit configured to measure a heart rate using the pair of measurement electrodes461, and a control unit configured to control output of the electrical stimulus supply unit based on the measured heart rate.

As the heart rate measurement unit detects a potential difference between the pair of measurement electrodes461upon contact with the blood, variation in potential varied by electrical activity of the heart, i.e., an electrocardiographic signal, can be obtained. In addition, the heart rate measurement unit can measure a heart rate from a time interval of a time at which, for example, a magnitude or a variation rate of a potential of the electrocardiographic signal becomes larger than a predetermined threshold, based on a waveform of the obtained electrocardiographic signal.

The control unit decreases energy of the electrical stimulus output from the electrical stimulus supply unit or stops supply thereof when the heart is in a bradycardiac state the heart rate is less than a certain rate. Accordingly, a cardiac heat rate drop is suppressed, and the heart rate is increased. In addition, when the heart is in a tachycardiac state in which the heart rate is raised, energy of an electrical stimulus output from the electrical stimulus supply unit is increased. Accordingly, the vagus nerve passing through the vicinity of the vein is stimulated to decrease the heart rate.

When the electrode portion438of the electrode unit406of the embodiment having the above-mentioned configuration is placed in the vein such as the superior vena cava V1or the internal jugular vein P4, the pair of stimulation electrodes434contact the inner wall of the vein and at the same time the pair of measurement electrodes461abut the blood. Accordingly, the pair of measurement electrodes461obtain cardiac activity, in other words, an electrocardiographic signal. The electrostimulation device420connected to the pair of measurement electrodes461measures the heart rate of the patient P from the electrocardiographic signal, and adjusts the energy of the electrical stimulus applied to the vagus nerve VN such that the patient P has a predetermined heart rate.

As described above, according to the electrode unit406and the electrostimulation system405of the embodiment, the same effect as the electrode unit402and the electrostimulation system401of the eleventh embodiment can be accomplished.

Further, as the pair of measurement electrodes461and the second interconnection portion462are provided, the heart rate of the patient P can be measured from a potential difference between the pair of measurement electrodes461, and the energy of the electrical stimulus applied to the vagus nerve VN can be adjusted such that the patient P has a predetermined heart rate.

The electrostimulation device can observe that the patient P has extreme bradycardia, emit an alarm upon abnormality, and automatically vary electrical stimulus conditions to always maintain a state in which the heart rate is decreased by a certain ratio. In addition, according to activities of the patient P, even when the heart rate is varied, a predetermined amount of heartbeat drop effect, i.e., a reduction effect of a cardiac load, can always be maintained.

In comparison with the conventional electrocardiographic signal measured by installing an electrocardiogram pad on a body surface of the patient P, a heart electric waveform obtained via the blood of the present invention cannot be easily affected by noises due to the activities and can stably measure the heart rate.

In addition, electrical stimulus conditions varied by the electrostimulation device may include a magnitude, a frequency, a pulse width of an electrical stimulus pulse voltage or current, a stimulus termination time, a stimulus start time, a stimulus continuation time, an electrical stimulus stop, or the like.

Further, in the embodiment, while the stimulation electrode434and the measurement electrode461are formed at the different wire portions433, the stimulation electrode434and the measurement electrode461may be formed at one wire portion433. Here, the measurement electrodes461are formed at the leading end attachment431side and the base end attachment432side to sandwich the pair of stimulation electrodes434, and an increase in an electrode interval between the measurement electrodes461enables acquisition of a good electrocardiogram waveform.

FIG. 78shows an example of the pair of measurement electrodes461ahaving different configurations. The measurement electrode461ahas two electrodes having an arcuate shape and formed of platinum iridium, which are installed at the outer circumferential side surfaces of the leading end attachment431. Even in the embodiment, the measurement electrode461acan contact the blood, and can measure the heart rate of the patient P from the potential difference between the measurement electrodes461a. Further, as a direction in which the respective electrodes of the measurement electrodes461aare bound coincides with a direction (a left/right horizontal direction of the superior vena cava) coinciding with the direction from the right ventricle to the left ventricle direction of the heart, a behavior of the heart can be easily detected as a large heart electric waveform.

Next, while a fourteenth embodiment of the present invention will be described with reference toFIGS. 79 and 80, like elements in the embodiment are designated by like reference numerals, description thereof will be omitted, and only differences will be described.

As shown inFIGS. 79 and 80, in an electrode unit408used in an electrostimulation system407of the embodiment, a leading end through-hole431bpassing on the axis C1is formed at the leading end attachment431of the electrode unit402of the eleventh embodiment.

A cross section of the inner surface of the leading end through-hole431bperpendicular to the axis C1has an oval shape.

In the electrostimulation system407of the embodiment, a stilet (a shaft-shaped member) S is inserted into the pipeline436bof the liquid feed tube436and the leading end through-hole431band used. When the stilet S is inserted into the leading end through-hole431b, the stilet S is used to sufficiently protrude in front of the leading end attachment431. A cross section of an outer surface of a section S1inserted into the leading end through-hole431bin the stilet S has an oval shape slightly smaller than the cross section of the above-mentioned leading end through-hole431b. The stilet S has strength such that certain flexibility can be provided and a torque about a central axis thereof can be transmitted. A member having substantially a hemispherical shape and no probability of damage to the vein inner wall may be used as a leading end portion of the stilet S.

A procedure using the electrostimulation system407having the above-mentioned configuration is performed as follows.

That is, outside of the body of the patient P, the stilet S is inserted into the pipeline436bof the liquid feed tube436and the leading end through-hole431bof the leading end attachment431. Then, the electrode portion438is placed in a target vein. Since the stilet S has flexibility, in the vein, the stilet S can be easily bent with the electrode unit408. In addition, when the electrode portion438is placed, as the electrode portion438extends in the axis C1direction, the leading end attachment431moves forward with respect to the stilet S. However, since the stilet S sufficiently protrudes in front of the leading end attachment431, the leading end attachment431is not dropped from the stilet S.

After the electrode portion438is schematically disposed, the operator grips both of the lead main body445and the stilet S to pivot them about a central axis C2of the stilet S. Then, as the section S1of the stilet S is engaged with the inner surface of the leading end through-hole431b, the electrode portion438is pivoted about the axis C1with the stilet S.

In addition, after the direction of the electrode portion438is adjusted, the stilet S is extracted from the liquid feed tube436, and a flow path configured to supply the anticoagulant agent is secured.

As described above, according to the electrode unit408and the electrostimulation system407of the embodiment, the same effect as the embodiment can be accomplished.

Further, a rotational force acted by the operator can be effectively transmitted to the electrode portion438via the stilet S, and a direction about the axis C1of the electrode portion438can be adjusted for a short time.

Furthermore, in this embodiment, a cross section of the inner surface of the leading end through-hole431bperpendicular to the axis C1has an oval shape. However, the cross section is not limited to the oval shape but may be a convex polygonal shape such as a rectangular shape as long as the polygonal shape is not a circular shape. In this case, a cross section of the outer surface of the section S1of the stilet S has a shape slightly smaller than the cross section of the inner surface of the leading end through-hole31bto be engaged with the inner surface of the leading end through-hole431b.

As described above, while the eleventh embodiment to the fourteenth embodiment of the present invention have been described in detail with reference to the drawings, a specific configuration is not limited to the embodiments but includes modifications of components within the scope without departing from the gist of the present invention. Further, it is needless to say that the respective components shown in the embodiments can be appropriately assembled and used.

For example, like an electrode unit411shown inFIG. 81, an extent to which some wire portions433of four wire portions433are bent to be spaced apart from the axis C1may be smaller than that of the other wire portions433.

In addition, as shown inFIG. 82, the number of wire portions433included in an electrode unit412is not limited but may be plural. As the number of wire portions433is increased, the electrode unit412can be stably placed in the vein. When placed in the vein having a large inner diameter, the number of wire portions433may be increased, and when placed in the vein having a small inner diameter, the number of wire portions433may be reduced.

The wire portions433may not be disposed about the axis C1at the same angular intervals, and the wire portions433may be disposed to support the tube wall of the vein about the axis C1.

Like an electrode unit413shown inFIGS. 83 and 84, the four wire portions473may have an S shape and an arcuate shape when seen from a front view. In this case, when seen to oppose the pair of stimulation electrodes434in a direction perpendicular to the axis C1, the pair of stimulation electrodes434are disposed such that a reference line C3passing through the pair of stimulation electrodes434crosses the axis C1.

When the electrode unit413having the above-mentioned configuration is placed in the vein, while the reference line C3is disposed to be inclined with respect to the axis C1, i.e., the longitudinal direction of the vein, it is effective when the vagus nerve VN is inclined and parallelly keeps pace with respect to the vein.

In addition, even both when the vagus nerves VN keeps pace in parallel with respect to the vein and when it inclinedly keeps pace with respect to the vein, the pair of stimulation electrodes434can be disposed to flank the vagus nerve VN, and the vagus nerve VN can be securely stimulated by the pair of stimulation electrodes434.

Further, when seen in a direction perpendicular to the axis C1, it is needless to say that a concept in which the reference line C3passing through the pair of stimulation electrodes434crosses the axis C1is not limited to the embodiment, but may be realized in various shapes by a crossing angle of the reference line C3or a shape of the wire portion.

Furthermore, it is needless to say that the above-mentioned measurement electrode461may be formed at the axis C1side of the wire portion473at which the stimulation electrode434is not formed.

In addition, in an electrode unit414shown inFIG. 85, the pair of stimulation electrodes434are formed at two of the four wire portions475one by one. The reference line C3passing through the pair of stimulation electrodes434is disposed to cross the axis C1as described above, and similarly, is effective when the vagus nerve VN inclinedly keeps pace with respect to the vein.

Further, in the eleventh embodiment to the fourteenth embodiment, the pair of stimulation electrodes434or the pair of measurement electrodes461may be plurally installed at two or more wire portions433. Here, as the IS1 type of connectors corresponding to the number of pairs of the stimulation electrodes434and the measurement electrodes461are installed at the base end portion of the lead main body and the connector connected to the electrostimulation device is selected, the stimulation electrode434at an appropriate position or the measurement electrode461at which the heart electric waveform can be largely detected is appropriately selected, and more effective nerve stimulation can be started for a shorter time.

In addition, coating for preventing solidification of the blood is of course effectively performed on outer surfaces of the attachments431and432, the wire portion, the lead main body, or the like.

The electrostimulation system introduces the electrode unit from the opening P1in the vicinity of the neck. However, the electrode unit may be introduced into the body from the opening or the like formed under the vicinity of the clavicle.

While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made within the scope without departing from the gist or scope of the present invention.

Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.