MEDICAL DEVICE AND METHOD FOR FORMING SHUNT

A medical device and a method for forming a shunt configured to effectively cauterize a biological tissue having a variation in thickness. The medical device includes an expansion body, an elongated shaft portion to which the proximal end of the expansion body is fixed, a plurality of energy transfer elements disposed along the expansion body, and a pulling shaft are included, and the expansion body, which has a recess that defines a reception space, is configured such that an easy-to-deform portion that is disposed on the expansion body and is easily deformable is deformed to enlarge the reception space at the position corresponding to the easy-to-deform portion in the circumferential direction when a force in the axial direction of the expansion body is received.

TECHNOLOGICAL FIELD

The present disclosure generally relates to a medical device including an expansion body that expands in a living body and a method for forming a shunt.

BACKGROUND DISCUSSION

Chronic heart failure is a known heart disease. Chronic heart failure is broadly classified into a systolic heart failure and a diastolic heart failure on the basis of a cardiac function index. In a patient suffering from the diastolic heart failure, myocardial hypertrophy appears and stiffness (hardness) increases, whereby blood pressure increases in a left atrium and a cardiac pumping function is deteriorated. As a result, the patient may show heart failure symptoms such as a pulmonary edema. In addition, there is also a heart disease in which, due to pulmonary hypertension or the like, blood pressure increases on a right atrium side and the cardiac pumping function is deteriorated to exhibit heart failure symptoms.

In recent years, shunt treatments have attracted attention. For those patients who suffer from heart failure, a shunt (through-hole) serving as an escape route for increased atrial pressure is formed in an atrial septum, thereby helping alleviate heart failure symptoms. In the shunt treatment, the atrial septum is accessed using an intravenous approaching method, and the through-hole is formed to a desired size. Examples of a medical device for performing such a shunt treatment for the atrial septum include a device as disclosed in International Patent Application Publication No. WO 2020/094094 A.

In a medical device disclosed in International Patent Application Publication No. WO 2020/094094 A, a biological tissue is sandwiched between two expandable expansion bodies around an axis of an elongated shaft, and electrode portions, which are a plurality of energy transfer elements arranged in a circumferential direction of one of the expansion bodies, are brought into contact with the biological tissue to be arranged in a circumferential direction of a hole of the biological tissue to be treated, and then energy is applied from the plurality of electrode portions to cauterize the biological tissue. However, when thickness of the biological tissue varies in the circumferential direction of the expansion body, the electrode portions sandwiching a thin part of the biological tissue may be separated from the biological tissue. In addition, when the electrode portions are not sufficiently in contact with the tissue to be treated, sufficient energy may not be applied to the biological tissue, which may deteriorate the treatment effect.

SUMMARY

A medical device and a method are disclosed for forming a shunt configured to effectively cauterize a biological tissue having a variation in thickness.

A medical device according to the present disclosure includes: an expansion body that has a distal end part including a force receiving portion and is expandable/contractible in a radial direction; an elongated shaft portion having a distal end part to which a proximal end of the expansion body is fixed; a plurality of energy transfer elements disposed along the expansion body; and a pulling shaft that is disposed inside the shaft portion, connectable to the force receiving portion of the expansion body by protruding from the distal end part of the shaft portion, and slidable with respect to the shaft portion, in which the expansion body includes: a first expansion portion having a distal-side expansion portion extending radially outward from the force receiving portion toward a direction of the proximal end and a distal-side top portion disposed on a proximal side of the distal-side expansion portion and convexly curved radially outward; a second expansion portion having a proximal-side expansion portion extending radially outward from the distal end part of the shaft portion toward a direction of the distal end and a proximal-side top portion disposed on a distal side of the proximal-side expansion portion and convexly curved radially outward; and a recess that is recessed radially inward, extends to couple the proximal-side top portion with the distal-side top portion, and defines a reception space configured to receive a biological tissue when the expansion body is expanded, the recess has a bottom portion located on an innermost side in the radial direction, a distal-side upright portion extending radially outward from a distal end of the bottom portion to the distal-side top portion, and a proximal-side upright portion extending radially outward from a proximal end of the bottom portion to the proximal-side top portion, one of the distal-side upright portion or the proximal-side upright portion includes a plurality of energy transfer element arrangement portions on which the plurality of individual energy transfer elements is disposed at substantially regular intervals in a circumferential direction of the expansion body, the other one of the distal-side upright portion or the proximal-side upright portion includes a plurality of facing portions facing the plurality of individual energy transfer elements when the expansion body is expanded, the distal-side expansion portion includes a plurality of distal-side strut structures coupled to the distal-side top portion, the proximal-side expansion portion includes a plurality of proximal-side strut structures coupled to the proximal-side top portion, at least one of the distal-side strut structures, the proximal-side strut structures, the energy transfer element arrangement portions, or the facing portions have easy-to-deform portions configured to be deformed more easily than other portions of the distal-side strut structures, the proximal-side strut structures, the energy transfer element arrangement portions, or the facing portions when a force in an axial direction of the expansion body is received, and each of the easy-to-deform portions deforms to enlarge the reception space at a position corresponding to the easy-to-deform portion in the circumferential direction.

A method for forming a shunt according to the present disclosure can form, in an oval fossa, a shunt through which a right atrium communicates with a left atrium using a medical device including an expansion body that has a distal end part including a force receiving portion and is expandable/contractible in a radial direction, an elongated shaft portion having a distal end part to which a proximal end of the expansion body is fixed, a plurality of energy transfer elements disposed along the expansion body, and a pulling shaft that is disposed inside the shaft portion, connectable to the force receiving portion of the expansion body by protruding from the distal end part of the shaft portion, and slidable with respect to the shaft portion, in which the expansion body includes a first expansion portion having a distal-side expansion portion extending radially outward from the force receiving portion toward a direction of the proximal end and a distal-side top portion disposed on a proximal side of the distal-side expansion portion and convexly curved radially outward, a second expansion portion having a proximal-side expansion portion extending radially outward from the distal end part of the shaft portion toward a direction of the distal end and a proximal-side top portion disposed on a distal side of the proximal-side expansion portion and convexly curved radially outward, and a recess that is recessed radially inward, extends to couple the proximal-side top portion with the distal-side top portion, and defines a reception space configured to receive a biological tissue when the expansion body is expanded, the recess has a bottom portion located on an innermost side in the radial direction, a distal-side upright portion extending radially outward from a distal end of the bottom portion to the distal-side top portion, and a proximal-side upright portion extending radially outward from a proximal end of the bottom portion to the proximal-side top portion, one of the distal-side upright portion or the proximal-side upright portion includes a plurality of energy transfer element arrangement portions on which the plurality of individual energy transfer elements is disposed at substantially regular intervals in a circumferential direction of the expansion body, the other one of the distal-side upright portion or the proximal-side upright portion includes a plurality of facing portions facing the plurality of individual energy transfer elements when the expansion body is expanded, the distal-side expansion portion includes a plurality of distal-side strut structures coupled to the distal-side top portion, the proximal-side expansion portion includes a plurality of proximal-side strut structures coupled to the proximal-side top portion, and at least one of the distal-side strut structures, the proximal-side strut structures, the energy transfer element arrangement portions, or the facing portions have easy-to-deform portions configured to be bent more easily than other portions of the distal-side strut structures, the proximal-side strut structures, the energy transfer element arrangement portions, or the facing portions when a force in an axial direction of the expansion body is received, the method including: inserting the medical device from an inferior vena cava into the right atrium; inserting the expansion body in a contracted state into a hole formed in the oval fossa; expanding the expansion body in the hole to dispose the biological tissue surrounding the hole in the reception space defined by the recess; sliding the pulling shaft in the direction of the proximal end with respect to the shaft portion to compress the expansion body such that the distal-side upright portion and the proximal-side upright portion of the recess approach each other; changing, according to thickness of the biological tissue surrounding the hole, a distance between the distal-side upright portion and the proximal-side upright portion in the circumferential direction of the expansion body on the basis of deformation of the easy-to-deform portion to bring the energy transfer elements disposed to face the recess along the distal-side upright portion or the proximal-side upright portion of the recess into contact with the biological tissue; and cauterizing the biological tissue disposed in the reception space using the energy transfer elements in contact with the biological tissue to inhibit occlusion due to natural healing of the hole.

According to the medical device and the method for forming a shunt configured as described above, the easy-to-deform portion deforms when the force in the axial direction acts on the expansion body so that the reception space at the position in the circumferential direction corresponding to the easy-to-deform portion enlarges. Thus, by deforming the easy-to-deform portion, it becomes possible to appropriately bring the plurality of energy transfer elements, which is arranged in the recess defining the reception space, into contact with the biological tissue having variations in thickness Therefore, the present medical device and the method for forming a shunt are enabled to rather effectively cauterize the biological tissue having variations in thickness.

The easy-to-deform portion may have bending rigidity lower than that of the other portions of the distal-side strut structure, the proximal-side strut structure, the energy transfer element arrangement portion, or the facing portion. With this arrangement, the force in the axial direction acts on the expansion body and the easy-to-deform portion is bent, whereby the reception space at the position in the circumferential direction corresponding to the easy-to-deform portion may be rather effectively enlarged.

The easy-to-deform portion may have an opening penetrating in the radial direction of the expansion body. With this arrangement, it becomes possible to relatively easily set the easy-to-deform portion, which can be easily bent, in the expansion body.

The easy-to-deform portion may have a thin portion having thickness in the radial direction of the expansion body smaller than that of an adjacent portion of the expansion body. With this arrangement, it becomes possible to relatively easily set the easy-to-deform portion, which can be easily bent, in the expansion body. Furthermore, it becomes possible to easily define the direction in which the easy-to-deform portion is bent.

The easy-to-deform portion may have a flexible portion made of a material more flexible than a material of an adjacent portion of the expansion body. With this arrangement, the bending rigidity of the easy-to-deform portion may be easily lowered.

The easy-to-deform portion may be sandwiched between rigid portions having the bending rigidity higher than that of the easy-to-deform portion in the axial direction of the expansion body. With this arrangement, it becomes possible to concentrate the stress on the easy-to-deform portion when the force in the axial direction acts on the expansion body so that the easy-to-deform portion may be easily bent.

The easy-to-deform portion may have a bent portion bent in a natural state. With this arrangement, it becomes possible to concentrate the stress on the bent portion when the force in the axial direction acts on the expansion body so that the easy-to-deform portion may be easily bent.

A medical device according to another aspect of the present disclosure includes: an expansion body that is expandable/contractible in a radial direction; an elongated shaft portion having, in a distal end part, a proximal-end fixing portion to which a proximal end of the expansion body is fixed; a pulling shaft that is disposed inside the shaft portion, connected to a distal end part of the expansion body by protruding from the distal end part of the shaft portion, and slidable with respect to the shaft portion; a distal-end shaft portion that extends inside the expansion body from a proximal end part to the distal end part of the expansion body; and an electrode portion disposed along the expansion body, in which the expansion body includes a recess that is recessed radially inward and defines a reception space configured to receive a biological tissue when the expansion body is expanded, the recess has a bottom portion located on an innermost side in the radial direction, a distal-side upright portion extending radially outward from a distal end of the bottom portion, and a proximal-side upright portion extending radially outward from a proximal end of the bottom portion, the electrode portion is disposed along the distal-side upright portion or the proximal-side upright portion to face the reception space, the pulling shaft is configured to apply, to the expansion body, a compressive force that makes compression along an axial center of the shaft portion such that the distal-side upright portion and the proximal-side upright portion approach each other by sliding in a direction of the proximal end with respect to the shaft portion, and in a state where the expansion body is expanded, the distal-end shaft portion includes a flexible portion configured to be bent at a center in an axial direction, a distal-end rigid portion disposed on a side distal of the flexible portion in the axial direction, and a proximal-end rigid portion disposed on a side proximal of the flexible portion in the axial direction.

A method for forming a shunt according to another aspect of the disclosure can form, in an oval fossa, a shunt through which a right atrium communicates with a left atrium using a medical device including an expansion body that is expandable/contractible in a radial direction, an elongated shaft portion having, in a distal end part, a proximal-end fixing portion to which a proximal end of the expansion body is fixed, a pulling shaft that is disposed inside the shaft portion, connected to a distal end part of the expansion body by protruding from the distal end part of the shaft portion, and slidable with respect to the shaft portion, a distal-end shaft portion that extends inside the expansion body from a proximal end part to the distal end part of the expansion body, and an electrode portion disposed along the expansion body, in which, in a state where the expansion body is expanded, the distal-end shaft portion includes a flexible portion configured to be bent at a center in an axial direction, a distal-end rigid portion disposed on a side distal of the flexible portion in the axial direction, and a proximal-end rigid portion disposed on a side proximal of the flexible portion in the axial direction, the method including: inserting the medical device from an inferior vena cava into the right atrium; inserting the expansion body in a contracted state into a hole formed in the oval fossa; expanding the expansion body in the hole to dispose a biological tissue surrounding the hole in a reception space defined by a recess of the expansion body having a bottom portion located on an innermost side in the radial direction, a distal-side upright portion extending radially outward from a distal end of the bottom portion, and a proximal-side upright portion extending radially outward from a proximal end of the bottom portion; compressing, by sliding the pulling shaft in a direction of the proximal end with respect to the shaft portion, the expansion body such that the distal-side upright portion and the proximal-side upright portion of the recess approach each other to bend the flexible portion according to thickness of the biological tissue surrounding the hole; bringing the electrode portion disposed to face the recess along the distal-side upright portion or the proximal-side upright portion of the recess into contact with the biological tissue by bending of the flexible portion; and cauterizing the biological tissue disposed in the reception space using the electrode portion in contact with the biological tissue to inhibit occlusion due to natural healing of the hole.

According to another aspect of the medical device and the method for forming a shunt configured as described above, it becomes possible to, when thickness of a biological tissue to be in contact with an expansion body varies along a circumferential direction, bend a distal-end shaft portion at a portion of a flexible portion depending on the thickness of the biological tissue to deform the expansion body such that a recess is brought into contact with each of portions of the biological tissue having larger and smaller thicknesses. As a result, it becomes possible to reliably bring the electrode portion into contact with the biological tissue over the entire circumference.

The distal-end rigid portion and the proximal-end rigid portion may be formed of an outer pipe into which the pulling shaft is inserted, and the flexible portion may be formed of a portion of the pulling shaft exposed from the distal-end rigid portion and the proximal-end rigid portion. With this arrangement, the rigidity of the distal-end rigid portion and the proximal-end rigid portion may be sufficiently secured.

The proximal-end rigid portion may be formed of an outer pipe into which the pulling shaft is inserted, and the pulling shaft may include the flexible portion exposed to the side distal of the proximal-end rigid portion in the axial direction, and the distal-end rigid portion disposed on the side distal of the flexible portion in the axial direction. With this arrangement, it becomes possible to reduce the number of outer pipes to facilitate assembly.

The distal-end rigid portion may be formed of an outer pipe into which the pulling shaft is inserted, and the pulling shaft may include the flexible portion exposed to the side proximal of the distal-end rigid portion in the axial direction, and the proximal-end rigid portion disposed on the side proximal of the flexible portion in the axial direction. With this arrangement, it becomes possible to reduce the number of outer pipes to facilitate assembly.

The distal-end shaft portion may be formed of an outer pipe into which the pulling shaft is inserted, and the distal-end shaft portion may include the flexible portion, the distal-end rigid portion, and the proximal-end rigid portion. With this arrangement, it becomes possible to reduce the number of outer pipes while eliminating the need to process the pulling shaft.

The pulling shaft may include the flexible portion, the distal-end rigid portion, and the proximal-end rigid portion. With this arrangement, it becomes possible to form the distal-end rigid portion and the proximal-end rigid portion only with the pulling shaft, whereby the number of parts may be further reduced.

DETAILED DESCRIPTION

Set forth below with reference to the accompanying drawings is a detailed description of embodiments of a medical device including an expansion body that expands in a living body and a method for forming a shunt. Note that dimensional ratios in the drawings may be exaggerated and different from actual ratios for convenience of description. In addition, in the present specification, a side of a medical device to be inserted into a living body lumen is referred to as a “distal side” and a side to be operated is referred to as a “proximal side”.

First Embodiment

As illustrated inFIG.5, a medical device10according to a first embodiment is configured to enlarge a through-hole Hh formed in an atrial septum HA of a heart H of a patient, and to further perform a maintenance treatment for maintaining the enlarged through-hole Hh at the increased size.

As illustrated inFIG.1, the medical device10according to the first embodiment includes an elongated member20extending from a proximal end to a distal end, an expansion body21disposed on a distal end part of the elongated member20, and an operation unit23connected to a proximal end part of the elongated member20. An energy transfer element22(electrode portion) for performing the maintenance treatment described above is disposed on the expansion body21.

As illustrated inFIGS.1to3, the elongated member20includes a shaft portion31holding the expansion body21at a distal end part, an outer tube30that accommodates the shaft portion31, a pulling shaft33, and a pulling portion35fixed to the distal end of the pulling shaft33.

The shaft portion31is an elongated tubular body extending from the operation unit23to the expansion body21. A proximal end part of the shaft portion31is fixed to a distal end part of the operation unit23. A distal end part of the shaft portion31is fixed to a proximal end part of the expansion body21.

The outer tube30is an elongated tubular body covering the shaft portion31, and is movable forward and backward with respect to the shaft portion31in the axial direction (direction of the axial center of the elongated member20). The outer tube30is configured to accommodate the contracted expansion body21in the outer tube30in a state of being moved to the distal side of the elongated member20. With the outer tube30being moved to the proximal side from the state of accommodating the expansion body21, the expansion body21may be exposed.

The pulling shaft33is an elongated tubular body disposed inside the shaft portion31, and is movable forward and backward with respect to the shaft portion31in the axial direction. The pulling shaft33protrudes from the distal end of the shaft portion31toward the distal side, and protrudes from the distal end of the expansion body21toward the distal side. A distal end part of the pulling shaft33on a side distal of the expansion body21is fixed to the pulling portion35. A proximal end part of the pulling shaft33is drawn out to a side proximal of the operation unit23. A guide wire lumen is formed in the pulling shaft33along the axial direction, and a guide wire11(seeFIGS.5to7) may be inserted into the guide wire lumen.

The pulling portion35is an annular member fixed to an outer peripheral surface of a distal end part of the pulling shaft33, and protrudes radially outward from the outer peripheral surface of the pulling shaft33. The pulling portion35is not fixed to the expansion body21. The outer diameter of the pulling portion35is larger than the inner diameter of the distal end part of the expansion body21. Therefore, the pulling portion35is enabled to abut on the distal end part of the expansion body21from the distal side, pull the expansion body21toward the direction of the proximal end, and apply a compressive force for making compression along the axial direction of the shaft portion31to the expansion body21.

The operation unit23can include a housing40to be gripped by an operator, a dial41configured to be operated by the operator, and a conversion mechanism42that converts rotation of the dial41into movement in the axial direction. The dial41is rotatably coupled to the housing40. The dial41is partially exposed to the outside from an opening of the housing40so as to be operated by the operator. The pulling shaft33is held by the conversion mechanism42inside the operation unit23. The conversion mechanism42can move the holding pulling shaft33forward and backward along the axial direction in conjunction with the rotation of the dial41. For example, a rack and pinion mechanism may be used as the conversion mechanism42.

As illustrated inFIGS.2to4, the expansion body21includes a force receiving portion51disposed at the distal end of the expansion body21, a proximal-end connecting portion52disposed at the proximal end of the expansion body21, a first expansion portion53coupled to the force receiving portion51, a second expansion portion54coupled to the proximal-end connecting portion52, and a recess55disposed between the first expansion portion53and the second expansion portion54.

The force receiving portion51may be annular, and is configured to receive a force directed toward the direction of the proximal end from the pulling portion35disposed on the distal side. The proximal-end connecting portion52may be annular, and is fixed to the distal end part of the shaft portion31.

The first expansion portion53includes a distal-side expansion portion56extending radially outward from the force receiving portion51toward the direction of the proximal end, and a distal-side top portion57disposed on the proximal side of the distal-side expansion portion56and convexly curved radially outward.

The first expansion portion53includes a plurality of distal-side strut structures60extending radially outward from the force receiving portion51toward the direction of the proximal end and forming the distal-side expansion portion56.

Each of the plurality of distal-side strut structures60includes a first section61extending from the force receiving portion51toward the direction of the proximal end, and a second section62extending from the proximal end of the first section61toward the direction of the proximal end and coupled to the distal-side top portion57.

Each of the first sections61includes a first strut63extending from the force receiving portion51substantially parallel to the axial center of the expansion body21when viewed from the radial outside.

Each of the second sections62includes a plurality of second struts64bifurcated to spread in the circumferential direction of the expansion body21while extending from the proximal end of each of the first struts63toward the direction of the proximal end, and a first joint portion65and a second joint portion66coupled to the proximal end of the second strut64. The first joint portion65and the second joint portion66are alternately arranged at substantially regular intervals in the circumferential direction of the expansion body21at the time of expansion. Each of the first joint portion65and the second joint portion66is formed such that two second struts64, which are bifurcated from respective two first struts63arranged on the distal side and adjacent in the circumferential direction and are extending to approach each other, are joined together. The number of the first struts63disposed in the expansion body21can be, for example,12, which is twice the number of the energy transfer elements22. The number of the second struts64disposed in the expansion body21can be, for example,24, which is twice the number of the first struts63and four times the number of the energy transfer elements22. The number of the first struts63and the second struts64may be changed as appropriate.

Each of the first joint portions65is coupled to the distal-side top portion57disposed in the same phase as the energy transfer element22in the circumferential direction of the expansion body21with an auxiliary curved portion67that functions as a buffer portion interposed between the first joint portions65and the first distal-side top portion69. The auxiliary curved portion67is curved in a wavelike shape to be folded a plurality of times when viewed from the radial outside.

Each of the second joint portions66is coupled to the distal-side top portion57disposed in a different phase in the circumferential direction of the expansion body21with respect to the energy transfer element22with a connecting strut68extending substantially parallel to the axial center of the expansion body21interposed between the second joint portions66and the second distal-side top portion70when viewed from the radial outside.

Each of the second struts64functions as an easy-to-deform portion that is more easily deformed than an adjacent portion on the distal side. The first strut63(rigid portion) having rigidity higher than that of the second strut64is disposed on the distal side of the second strut64(easy-to-deform portion).

The two second struts64are coupled to, via a first distal-side top portion69, the distal side of the portion of the expansion body21on which the energy transfer element22is disposed. Those two second struts64are coupled to the two first struts63disposed on the distal side. Therefore, the sum of the rigidity of the two second struts64, which serve as the easy-to-deform portion with rigidity K1, can be equal to or lower than the sum of the rigidity of the two first struts63, which serve as the rigid portion with rigidity K2, and is preferably lower than the rigidity K2. In order to obtain such a second strut64, the width of the second strut64(length of the expansion body21in the circumferential direction) is set to be smaller than the width of the first strut63. The thickness of the second strut64(length of the expansion body21in the radial direction) may be set to be smaller than the thickness of the first strut63.

In addition, the rigidity K1of the easy-to-deform portion is preferably higher than rigidity K3of the first distal-side top portion69supported by those two second struts64, higher than rigidity K4of one bottom connecting portion83, and higher than rigidity K5of one top portion included in a proximal-side top portion59. This is because the bottom connecting portion83, the first distal-side top portion69, and the proximal-side top portion59need to be flexibly deformed for expansion of the expansion body21.

Note that a position at which the easy-to-deform portion is disposed is not limited to the second strut64of the distal-side strut structure60. The easy-to-deform portion may be disposed at a position other than the force receiving portion51, the proximal-end connecting portion52, the bottom portion71, the distal-side top portion57, and the proximal-side top portion59of the expansion body21. Therefore, the easy-to-deform portion is disposed on at least one of the distal-side strut structure60, a proximal-side strut structure90, an energy transfer element arrangement portion81, or a facing portion82.

Note that a rigid portion having rigidity higher than that of the second strut64and the first distal-side top portion69may also be disposed between the second strut64(easy-to-deform portion) and the distal-side top portion57. With this arrangement, the distal side and the proximal side of the second strut64are sandwiched between the rigid portions having rigidity higher than that of the second strut64, thereby being relatively easily bent due to stress concentration.

The distal-side top portion57includes a plurality of first distal-side top portions69coupled to the auxiliary curved portion67, and a plurality of second distal-side top portions70coupled to the connecting strut68. The first distal-side top portions69and the second distal-side top portions70are alternately arranged at substantially regular intervals in the circumferential direction of the expansion body21at the time of expansion.

The recess55is recessed radially inward when the expansion body21is expanded, and extends to couple the proximal-side top portion59with the distal-side top portion57. The recess55defines a reception space74configured to receive a biological tissue when the expansion body21is expanded.

The recess55includes the bottom portion71located on the innermost side in the radial direction, a distal-side upright portion72extending radially outward from the distal end of the bottom portion71to the distal-side top portion57, and a proximal-side upright portion73extending radially outward from the proximal end of the bottom portion71to the proximal-side top portion59.

The recess55includes a plurality of recessed strut structures80coupled to the plurality of distal-side strut structures60via the distal-side top portion57. Each of the plurality of recessed strut structures80includes the energy transfer element arrangement portion81disposed on the proximal-side upright portion73, and the facing portion82disposed on the distal-side upright portion72, and also includes the bottom connecting portion83that couples a pair of the energy transfer element arrangement portion81and the facing portion82in the bottom portion71. Each of the bottom connecting portions83is disposed in a phase different from that of the first strut63in the circumferential direction of the expansion body21.

A plurality of the energy transfer element arrangement portions81is disposed at substantially regular intervals in the circumferential direction of the expansion body21. The energy transfer element22is disposed on a surface of each of the energy transfer element arrangement portions81forming the inside of the recess55.

The individual facing portions82face the individual energy transfer elements22when the expansion body21is expanded. Each of the facing portions82includes a plurality of distal-side upright struts84bifurcated to spread toward the direction of the distal end and a plurality of backrest portions85substantially along the circumferential direction of the expansion body21from the distal end of each of the bottom connecting portions83. Each of the second distal-side top portions70is formed such that two distal-side upright struts84, which are disposed on the proximal side and are extending to approach each other from the respective two bottom connecting portions83adjacent in the circumferential direction, are joined together. The plurality of backrest portions85couples the two distal-side upright struts84bifurcated from each of the bottom connecting portions83. The plurality of backrest portions85is arranged side by side from the side closer to the bottom portion71to the side closer to the distal-side top portion57. Each of the backrest portions85is curved such that a part between both ends coupled to the two distal-side upright struts84protrudes toward the distal-side top portion57. Each of the backrest portions85is easily bent on the side closer to the distal-side top portion57with the both ends coupled to the distal-side upright struts84as supporting points. Therefore, the backrest portion85can be bent by a force toward the distal side received from the energy transfer element22disposed on the proximal-side upright portion73. Accordingly, the biological tissue sandwiched between the energy transfer element22and the backrest portion85can be brought into contact with the energy transfer element22. Among the plurality of backrest portions85forming each of the facing portions82, the backrest portion85closest to the distal-side top portion57is coupled to the first distal-side top portion69at the part protruding toward the distal-side top portion57. Note that the number of the backrest portions85forming each of the facing portions82is not particularly limited.

The second expansion portion54includes a proximal-side expansion portion58extending radially outward from the proximal-end connecting portion52toward the direction of the distal end, and the proximal-side top portion59disposed on the distal side of the proximal-side expansion portion58and convexly curved radially outward.

The proximal-side expansion portion58includes a plurality of proximal-side strut structures90. Each of the proximal-side strut structures90is disposed in the same phase as the plurality of energy transfer element arrangement portions81in the circumferential direction of the expansion body21. Each of the plurality of proximal-side strut structures90includes a plurality of third struts91extending from the distal end part of the shaft portion31to the proximal-side top portion59substantially parallel to the axial center of the expansion body21when viewed from the radial outside, and a plurality of secondary struts92coupling the third struts91adjacent in the circumferential direction. Each of the secondary struts92includes two support struts93joined to, at a junction94, individual two third struts91adjacent in the circumferential direction. The two support struts93are coupled to have an angle between two junctions94. Thus, each of the secondary struts92is formed to be longer than the linear distance between the two junctions94. With this arrangement, even when the distance between the two junctions94increases at the time of expansion of the expansion body21, the secondary strut92can continuously support the two third struts91while changing the angle between the two support struts93included in the secondary strut92. Therefore, the expansion body21is enabled to expand by the compressive force applied by the pulling shaft33while expanding the third struts91at substantially regular intervals.

An interval between the proximal-side upright portion73and the distal-side upright portion72is preferably slightly larger in the axial direction on the outer side than the inner side in the radial direction when the expansion portion is expanded. With this arrangement, the biological tissue can be rather easily arranged between the proximal-side upright portion73and the distal-side upright portion72from the radial outside.

The energy transfer element22is disposed on a surface toward the distal side of the proximal-side upright portion73when the expansion portion is expanded. Since the energy transfer element22is disposed on the proximal-side upright portion73, energy from the energy transfer element22is transmitted to the atrial septum HA from the right atrium side when the recess55sandwiches the atrial septum HA. In a case where the energy transfer element22is disposed on the distal-side upright portion72, the energy from the energy transfer element22is transmitted to the atrial septum HA from the left atrium side.

The energy transfer element22can include, for example, a bipolar electrode that receives electric energy from an energy supply device, which is an external device. In this case, electricity is conducted between the energy transfer elements22disposed on individual arrangement portions of the energy transfer elements22. The energy transfer element22and the energy supply device are connected to each other by a conductive wire coated with an insulating coating material. The conductive wire is drawn out (i.e., extends) to the outside via the elongated member20and the operation unit23, and is connected to the energy supply device.

Alternatively, the energy transfer element22may be configured as a monopolar electrode. In this case, electricity is supplied from a counter electrode plate prepared outside a body. Furthermore, the energy transfer element22may be a heating element (electrode chip) that receives high-frequency electric energy from the energy supply device and generates heat. In this case, electricity is conducted between the energy transfer elements22disposed on individual wire rod portions. Moreover, the energy transfer element22may include an element configured to apply energy to the through-hole Hh, such as a heater including an electric wire or the like that provides heating and cooling operation or generates frictional heat by using microwave energy, ultrasound energy, coherent light such as laser, a heated fluid, a cooled fluid, or a chemical medium, and a specific form is not particularly limited.

While the energy transfer element22and the backrest portion85are disposed on the proximal-side upright portion73and the distal-side upright portion72, respectively, in the present embodiment, the energy transfer element22and the backrest portion85may be disposed on the distal-side upright portion72and the proximal-side upright portion73, respectively.

The expansion body21can be, for example, cut out from a pipe to be integrally formed. The struts forming the expansion body21may have a thickness, for example, in a range of 50 μm to 500 μm and a width, for example, in a range of 0.3 mm to 2.0 mm. However, the struts forming the expansion body21may have dimensions outside the ranges as set forth above. In addition, a shape of the struts is not particularly limited, and may be, for example, a circular cross-sectional shape or another cross-sectional shape.

The expansion body21may be formed of a metal material. Examples of the metal material that may be used include a titanium-based (Ti—Ni, Ti—Pd, Ti—Nb—Sn, etc.) alloy, a copper-based alloy, stainless steel, p-titanium steel, and a Co—Cr alloy. Note that an alloy having a spring property, such as a nickel titanium alloy, or the like may be more preferably used. However, a material of the wire rod portions is not limited to the above materials, and the wire rod portions may be formed of other materials.

The outer tube30and the shaft portion31of the elongated member20are preferably formed of a material having a certain degree of flexibility. Examples of such a material having a certain degree of flexibility of the outer tube30and the shaft portion31of the elongated member can include polyolefin such as polyethylene, polypropylene, polybutene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ionomer, or a mixture of two or more of them, soft polyvinyl chloride resin, polyamide, polyamide elastomer, polyester, polyester elastomer, polyurethane, fluorine resin such as polytetrafluoroethylene, polyimide, polyetheretherketone (PEEK), silicone rubber, and latex rubber.

The pulling shaft33and the pulling portion35may be formed of, for example, an elongated wire rod including a super elasticity alloy such as a nickel-titanium alloy and a copper-zinc alloy, a metal material such as stainless steel, a resin material having comparatively high rigidity, or the like. Furthermore, the pulling shaft33and the pulling portion35may be formed of the materials described above coated with a resin material such as polyvinyl chloride, polyethylene, polypropylene, ethylene-propylene copolymer, fluorine resin, or the like.

Next, a method for forming a shunt using the medical device10according to the first embodiment will be described with reference to a flowchart illustrated inFIG.10. The present method for forming a shunt is performed on a patient suffering from heart failure (left heart failure). More specifically, as illustrated inFIG.5, the present method is a treatment method to be performed on a patient suffering from chronic heart failure in which myocardial hypertrophy appears in a left ventricle of the heart H and stiffness (hardness) increases so that blood pressure increases in a left atrium HLa.

The treatment method according to the present embodiment includes forming the through-hole Hh in the atrial septum HA (S1), disposing the expansion body21in the through-hole Hh (S2), receiving a biological tissue in the reception space74(S3), enlarging the diameter of the through-hole Hh using the expansion body21(S4), confirming hemodynamics in the vicinity of the through-hole Hh (S5), performing the maintenance treatment for maintaining the size of the through-hole Hh (S6), and confirming the hemodynamics in the vicinity of the through-hole Hh after the maintenance treatment (S7).

At the time of forming the through-hole Hh, the operator delivers, to the vicinity of the atrial septum HA, an introducer in which a guiding sheath and a dilator are combined with each other. For example, the introducer may be delivered to a right atrium HRa via an inferior vena cava Iv. In addition, the introducer may be delivered using the guide wire11. The operator may insert the guide wire11into the dilator and deliver the introducer along the guide wire11. Note that the introducer and the guide wire11may be inserted into a living body using a method such as a method of using an introducer to be introduced into a blood vessel.

In the step of S1, the operator causes a puncture device to penetrate from the side of the right atrium HRa toward the side of the left atrium HLa to form the through-hole Hh. As the puncture device, a device such as a wire having a sharp distal end maybe used, for example. The puncture device is inserted into the dilator, and is delivered to the atrial septum HA. The puncture device may be delivered to the atrial septum HA instead of the guide wire11after the guide wire11is removed from the dilator.

Next, the operator delivers a balloon catheter150to the vicinity of the atrial septum HA along the guide wire11inserted in advance. As illustrated inFIG.6, the balloon catheter150includes a balloon152at a distal end part of a shaft portion151. When the balloon152is placed in the atrial septum HA, it is expanded in the radial direction to enlarge the through-hole Hh.

As illustrated inFIG.7, in the step of S2, the medical device10is delivered to the vicinity of the atrial septum HA along the guide wire11inserted in advance. At this time, the distal end part of the medical device10penetrates the atrial septum HA and reaches the left atrium HLa. In addition, when the medical device10is inserted, the expansion body21is in a state of being housed in the outer tube30.

Next, in the step of S3, the outer tube30is moved to the proximal side to expose the expansion body21. As a result, as illustrated inFIG.8, the diameter of the expansion body21increases and the recess55is arranged in the through-hole Hh of the atrial septum HA to receive the biological tissue surrounding the through-hole Hh in the reception space74. The through-hole Hh is maintained in a state of being enlarged by the expansion body21.

In the step of S4, the operator operates the operation unit23in the state where the atrial septum HA is received in the reception space74of the recess55, moves the pulling shaft33to the proximal side, and sandwiches the biological tissue with the recess55of the expansion body21, as illustrated inFIG.9. Meanwhile, the thickness of the atrial septum HA (biological tissue) may be non-uniform in the circumferential direction. Each of the plurality of recessed strut structures80including the energy transfer element arrangement portion81, the bottom connecting portion83, and the facing portion82is independently deformable. In addition, the second strut64(easy-to-deform portion) is coupled to the distal side of each of the recessed strut structures80via the distal-side top portion57. Thus, each of the recessed strut structures80may independently change the gap between the energy transfer element arrangement portion81and the facing portion82while deforming the second strut64depending on the thickness of the atrial septum HA sandwiched by the recessed strut structures80. Therefore, the separation distance between the energy transfer element arrangement portion81and the facing portion82in the recessed strut structure80sandwiching the atrial septum HA partially thick in the circumferential direction is larger than the separation distance between the energy transfer element arrangement portion81and the facing portion82in the recessed strut structure80sandwiching the atrial septum HA partially thin in the circumferential direction. At this time, the second strut64coupled to, via the distal-side top portion57, the distal side of the recessed strut structure80sandwiching the atrial septum HA partially thick in the circumferential direction is bent more than other second struts64. Therefore, even when the thickness of the atrial septum HA is non-uniform in the circumferential direction, all the energy transfer elements22arranged in the recess55can be appropriately brought into contact with the atrial septum HA.

After the expansion body21is disposed in the through-hole Hh, the hemodynamics is checked in the step of S5. As illustrated inFIG.5, the operator delivers a hemodynamics checking device100to the right atrium HRa via the inferior vena cava Iv. For example, an echo catheter may be used as the hemodynamics checking device100. The operator can display an echo image obtained by the hemodynamics checking device100on a display device, such as a display, and can check blood volume passing through the through-hole Hh on the basis of a displayed result.

Next, in the step of S6, the operator performs the maintenance treatment for maintaining the size of the through-hole Hh. In the maintenance treatment, high-frequency energy is applied to an edge portion of the through-hole Hh through the energy transfer element22, thereby cauterizing (heating and cauterizing) the edge portion of the through-hole Hh with the high-frequency energy.

The energy transfer element22in contact with the thick portion of the atrial septum HA is brought into firm contact in a similar manner to other energy transfer elements22as the second strut64corresponding to the energy transfer element22deforms. Thus, even when the thickness of the atrial septum HA is non-uniform in the circumferential direction, all the energy transfer elements22arranged in the recess55are appropriately brought into contact with the atrial septum HA. Therefore, according to the maintenance treatment, the entire edge portion of the through-hole Hh in the circumferential direction may be appropriately cauterized. In addition, the energy transfer elements22to which the current is supplied may be suppressed from being exposed to a blood vessel without being in contact with the biological tissue, whereby thrombus formation may be suppressed.

When the biological tissue in the vicinity of the edge portion of the through-hole Hh is cauterized through the energy transfer element22, a degenerated portion in which the biological tissue is degenerated is formed in the vicinity of the edge portion. The biological tissue in the degenerated portion loses elasticity so that the through-hole Hh is enabled to maintain the shape enlarged by the expansion body21.

The hemodynamics is checked again in the step of S7after the maintenance treatment, and in a case where the blood volume passing through the through-hole Hh reaches desired volume, the operator decreases the diameter of the expansion body21, stores the expansion body21in the outer tube30, and removes it from the through-hole Hh. Moreover, the operator removes the entire medical device10from the living body to the outside of the living body, and terminates the treatment.

As described above, the medical device10according to the first embodiment includes: the expansion body21that has a distal end part including the force receiving portion51and is expandable/contractible in the radial direction; the elongated shaft portion31having a distal end part to which the proximal end of the expansion body21is fixed; the plurality of electrode portions (energy transfer elements22) disposed along the expansion body21; and the pulling shaft33that is disposed inside the shaft portion31, connectable to the force receiving portion51of the expansion body21by protruding from the distal end part of the shaft portion31, and slidable with respect to the shaft portion31, in which the expansion body21includes: the first expansion portion53having the distal-side expansion portion56extending radially outward from the force receiving portion51toward the direction of the proximal end and the distal-side top portion57disposed on the proximal side of the distal-side expansion portion56and convexly curved radially outward; the second expansion portion54having the proximal-side expansion portion58extending radially outward from the distal end part of the shaft portion31toward the direction of the distal end and the proximal-side top portion59disposed on the distal side of the proximal-side expansion portion58and convexly curved radially outward; and the recess55that is recessed radially inward, extends to couple the proximal-side top portion59with the distal-side top portion57, and defines the reception space74configured to receive a biological tissue when the expansion body21is expanded, the recess55has the bottom portion71located on the innermost side in the radial direction, the distal-side upright portion72extending radially outward from the distal end of the bottom portion71to the distal-side top portion57, and the proximal-side upright portion73extending radially outward from the proximal end of the bottom portion71to the proximal-side top portion59, one of the distal-side upright portion72or the proximal-side upright portion73includes the plurality of energy transfer element arrangement portions81on which the plurality of individual electrode portions is disposed at substantially regular intervals in the circumferential direction of the expansion body21, the other one of the distal-side upright portion72or the proximal-side upright portion73includes the plurality of facing portions82facing the plurality of individual energy transfer elements22when the expansion body21is expanded, the distal-side expansion portion56includes the plurality of distal-side strut structures60coupled to the distal-side top portion57, the proximal-side expansion portion58includes the plurality of proximal-side strut structures90coupled to the proximal-side top portion59, at least one of the distal-side strut structures60, the proximal-side strut structures90, the energy transfer element arrangement portions81, or the facing portions82have the easy-to-deform portions configured to be deformed more easily than other portions of the distal-side strut structures60, the proximal-side strut structures90, the energy transfer element arrangement portions81, or the facing portions82when a force in the axial direction of the expansion body21is received, and each of the easy-to-deform portions deforms to enlarge the reception space74at the position corresponding to the easy-to-deform portion in the circumferential direction.

In the medical device10configured as described above, the easy-to-deform portion deforms when a force in the axial direction acts on the expansion body21so that the reception space74at a position in the circumferential direction corresponding to the easy-to-deform portion can be enlarged. Thus, by deforming the easy-to-deform portion, it becomes possible to appropriately bring the plurality of energy transfer elements22, which is arranged in the recess55defining the reception space74, into contact with the biological tissue having variations in thickness. Therefore, the medical device10may effectively cauterize the biological tissue having variations in thickness and may suppress thrombus formation.

Furthermore, the easy-to-deform portion has bending rigidity lower than that of other portions of the distal-side strut structure60, the proximal-side strut structure90, the energy transfer element arrangement portion81, and the facing portion82. With this arrangement, the force in the axial direction acts on the expansion body21and the easy-to-deform portion is bent, whereby the reception space74at the position in the circumferential direction corresponding to the easy-to-deform portion may be effectively enlarged.

Furthermore, the present disclosure also provides the method for forming a shunt. The method for forming a shunt is a method for forming a shunt that forms, in an oval fossa, a shunt (through-hole Hh) through which the right atrium HRa communicates with the left atrium HLa using the medical device10described above, the method including: inserting the medical device10from the inferior vena cava Iv into the right atrium HRa; inserting the expansion body21in the contracted state into the through-hole Hh formed in the oval fossa; expanding the expansion body21in the through-hole Hh to dispose the biological tissue surrounding the through-hole Hh in the reception space74defined by the recess55; sliding the pulling shaft33in the direction of the proximal end with respect to the shaft portion31to compress the expansion body21such that the distal-side upright portion72and the proximal-side upright portion73of the recess55approach each other; changing, according to thickness of the biological tissue surrounding the through-hole Hh, a distance between the distal-side upright portion72and the proximal-side upright portion73in the circumferential direction of the expansion body21on the basis of deformation of the easy-to-deform portion to bring the energy transfer elements22disposed to face the recess55along the distal-side upright portion72or the proximal-side upright portion73of the recess55into contact with the biological tissue; and cauterizing the biological tissue disposed in the reception space74using the energy transfer elements22in contact with the biological tissue to inhibit occlusion due to natural healing of the through-hole Hh.

According to the method for forming a shunt configured as described above, the easy-to-deform portion deforms when the force in the axial direction of the expansion body21is received, thereby cauterizing the biological tissue disposed in the reception space74using the energy transfer element22in contact with the biological tissue having variations in thickness. The method for forming a shunt may effectively cauterize the biological tissue having variations in thickness and may suppress thrombus formation.

The present disclosure is not limited to the embodiment described above, and various modifications may be made by those skilled in the art within the technical idea of the present disclosure. For example, the position at which the easy-to-deform portion is disposed is not limited to the distal-side strut structure60, and it may be disposed on the proximal-side strut structure90, the energy transfer element arrangement portion81, or the facing portion82. Furthermore, the easy-to-deform portion may be disposed on two or more positions selected from the distal-side strut structure60, the proximal-side strut structure90, the energy transfer element arrangement portion81, or the facing portion82.

Furthermore, the proximal-side strut structure90, the energy transfer element arrangement portion81, the facing portion82, and the distal-side strut structure60may be formed of one strut without branching and joining. Furthermore, the direction in which the easy-to-deform portion deforms is not particularly limited. Furthermore, the width of the strut may be partially changed so that the easy-to-deform portion is easily deformed when a predetermined force or more is applied.

Furthermore, as in a first modified example of the first embodiment illustrated inFIG.11A, the easy-to-deform portion may include a thin portion110whose thickness in the radial direction of the expansion body21is thinner than that of an adjacent portion of the expansion body21. The thin portion110is a portion in which the second moment of area is smaller than that in the adjacent portion of the expansion body21. With this arrangement, it becomes possible to rather easily set the easy-to-deform portion, which is easily bent, in the expansion body21. Furthermore, it becomes possible to rather easily define the direction in which the easy-to-deform portion is bent. Examples of the method for forming the thin portion110include a method of reinforcing a portion other than the thin portion110of the expansion body21with metal or resin, a method of swaging by applying a pressing force, a method of scraping, and the like.

Furthermore, the easy-to-deform portion may be sandwiched between rigid portions111having bending rigidity higher than that of the easy-to-deform portion in the axial direction of the expansion body21. With this arrangement, it becomes possible to concentrate the stress on the easy-to-deform portion when the force in the axial direction acts on the expansion body21so that the easy-to-deform portion may be easily bent.

Furthermore, as in a second modified example of the first embodiment illustrated inFIG.11B, the easy-to-deform portion may have an opening112penetrating in the radial direction of the expansion body21. With this arrangement, it becomes possible to rather easily set the easy-to-deform portion, which is easily bent, in the expansion body21. Note that the opening that decreases the bending rigidity of the expansion body21may also be formed in the distal-side top portion57, the proximal-side top portion59, and the bottom portion71.

Furthermore, as in a third modified example of the first embodiment illustrated inFIG.11C, the easy-to-deform portion may have a bent portion113bent in a natural state. The direction in which the bent portion113is bent is not particularly limited, and can be, for example, a direction along the radial direction of the expansion body21. With this arrangement, it becomes possible to concentrate the stress on the bent portion113when the force in the axial direction acts on the expansion body21so that the easy-to-deform portion may be easily bent. In a case where the easy-to-deform portion is easily deformed by being bent, the easy-to-deform portion does not necessarily have the bending rigidity lower than that of other portions of the distal-side strut structure60, the proximal-side strut structure90, the energy transfer element arrangement portion81, and the facing portion82.

Furthermore, as in a fourth modified example of the first embodiment illustrated inFIG.11D, the easy-to-deform portion may include a flexible portion114made of a material more flexible than the material of the adjacent portion of the expansion body21. For example, the flexible portion is made of resin, and the adjacent portion of the flexible portion114is made of metal, for example. With this arrangement, it becomes possible to easily set the easy-to-deform portion, which is easily bent, in the expansion body21.

Second Embodiment

As illustrated inFIGS.12and13, in a medical device10according to a second embodiment, a shaft portion31includes a distal-end shaft portion130including a proximal-end fixing portion131to which a proximal end of an expansion body21is fixed and a distal-end fixing portion133to which a distal end of the expansion body21is fixed. The distal-end shaft portion130extends inside the expansion body21from a proximal end part to a distal end part of the expansion body21. Note that components common to those of the medical device10according to the first embodiment are denoted by the same reference numerals, and descriptions of the components common those of the medical device10will be omitted to avoid duplication.

The distal-end shaft portion130includes a flexible portion160configured to be bent at the center in the axial direction in a state where the expansion body21is expanded, a distal-end rigid portion162disposed on a side distal of the flexible portion160in the axial direction, and a proximal-end rigid portion164disposed on a side proximal of the flexible portion160in the axial direction. The distal-end rigid portion162and the proximal-end rigid portion164are formed of a hard outer pipe into which a pulling shaft33may be inserted. The flexible portion160is formed by a portion of the pulling shaft33exposed from the distal-end rigid portion162and the proximal-end rigid portion164. Since the pulling shaft33is made of a bendable material, the flexible portion160may be bent by receiving a force. The distal-end rigid portion162and the proximal-end rigid portion164are made of a hard resin or metal to maintain a linear shape without being bent even when the flexible portion160receives a bending force.

Each of portions on which the proximal-end fixing portion131and the distal-end fixing portion133of the expansion body21are disposed is a binding portion at which a plurality of wire rod portions50converges, and the distal-end rigid portion162and the proximal-end rigid portion164extend toward the center in the axial direction from the proximal-end fixing portion131and the distal-end fixing portion133, respectively. The distal-end rigid portion162and the proximal-end rigid portion164have a length of at least equal to or longer than 30% of the axial length of the portion in which the wire rod portion50extends from the binding portion toward a recess55. In addition, the flexible portion160is disposed in a portion of the distal-end shaft portion130facing a bottom portion71of the recess55in the radial direction in the state where the expansion body21is expanded.

A treatment method using the medical device10according to the second embodiment is substantially similar to the treatment method using the medical device10according to the first embodiment. An operator grips an atrial septum HA with a proximal-side upright portion73and a distal-side upright portion72, and presses an electrode portion (energy transfer element22) against a biological tissue. In a case where the thickness of the biological tissue around a puncture hole Hh varies in a circumferential direction, as illustrated inFIG.14, the flexible portion160of the distal-end shaft portion130is bent according to the thickness of the biological tissue as the expansion body21is compressed by the pulling shaft33. As a result, the recess55of the expansion body21is brought into contact with the biological tissue over the entire circumference in the circumferential direction. Therefore, it becomes possible to reliably bring the electrode portion (energy transfer element22) into contact with the biological tissue. InFIG.14, the thickness of the biological tissue on the upper side in the drawing of the puncture hole Hh is larger, and the thickness of the biological tissue on the lower side in the drawing of the puncture hole Hh is smaller. In the distal-end shaft portion130, the flexible portion160is bent downward in the drawing according to the difference in thickness of the biological tissue. Accordingly, in the recess55of the expansion body21on the upper side in the drawing, the interval between the proximal-side upright portion73and the distal-side upright portion72is wider according to the larger thickness of the biological tissue, and in the recess55of the expansion body21on the lower side in the drawing, the interval between the proximal-side upright portion73and the distal-side upright portion72is narrower according to the smaller thickness of the biological tissue. Thus, both of the portions of the biological tissue having larger and smaller thicknesses are gripped by the recess55with the equivalent force, and the individual electrode portions (energy transfer element22) are brought into contact with the biological tissue with the equivalent force.

Since the distal-end shaft portion130includes the distal-end rigid portion162and the proximal-end rigid portion164and includes the bendable flexible portion160in the portion radially facing the bottom portion71of the recess55, it becomes possible to form a bent shape at the center of the distal-end shaft portion130in the axial direction. As a result, the expansion body21may be deformed such that the proximal-side upright portion73and the distal-side upright portion72approach each other depending on the thickness of the biological tissue along the circumferential direction of the recess55. While the bent shape at the center of the distal-end shaft portion130in the axial direction may not be formed when the distal-end shaft portion130is entirely formed of the flexible portion160so that the recess55fails to grip the biological tissue at least in a part in the circumferential direction, the bent shape at the center of the distal-end shaft portion130in the axial direction is achieved by the distal-end rigid portion162and the proximal-end rigid portion164being included in the distal-end shaft portion130, whereby the expansion body21may be deformed such that the recess55grips the biological tissue over the entire circumference. In order to form such a bent shape at the center of the distal-end shaft portion130in the axial direction, the distal-end rigid portion162and the proximal-end rigid portion164need to have a certain length. Accordingly, as described above, the distal-end rigid portion162and the proximal-end rigid portion164have a length of at least equal to or longer than 30% of the axial length of the portion in which the wire rod portion50extends from the binding portion toward the recess55.

Next, the operator checks hemodynamics (S5), inhibits occlusion due to natural healing of the puncture hole Hh, and performs a maintenance treatment to maintain the size thereof (S6). In the maintenance treatment, high-frequency energy is applied to an edge portion of the puncture hole Hh through the electrode portion (energy transfer element22), thereby cauterizing (heating and cauterizing) the edge portion of the puncture hole Hh with the high-frequency energy. The high-frequency energy is applied by a voltage being applied between a pair of electrode portions (energy transfer elements22) adjacent in the circumferential direction. As described above, since the distal-end shaft portion130is bent at the center in the axial direction so that the individual electrode portions (energy transfer elements22) are uniformly brought into contact with the biological tissue, it becomes possible to reliably apply the energy to the biological tissue over the entire circumference by applying a voltage to the electrode portions (energy transfer elements22) even when the thickness of the biological tissue surrounding the puncture hole Hh is different in the circumferential direction.

Next, a modified example of the distal-end shaft portion in the second embodiment will be described. As illustrated inFIG.15, a distal-end shaft portion136according to a fifth modified example in the second embodiment includes a flexible portion170in an intermediate portion in the axial direction, a distal-end rigid portion172on the side distal of the flexible portion170, and a proximal-end rigid portion174on the side proximal of the flexible portion170. The proximal-end rigid portion174is formed of a hard outer pipe into which the pulling shaft33is inserted. The pulling shaft33includes the flexible portion170exposed to the side distal of the proximal-end rigid portion174in the axial direction, and the distal-end rigid portion172disposed on the side distal of the flexible portion170in the axial direction. That is, the distal-end rigid portion172is formed on the pulling shaft33. The distal-end rigid portion172may be formed such that, for example, the surface of the flexibly formed pulling shaft33is coated with a hard tubular member. As described above, even when the distal-end rigid portion172is formed on the pulling shaft33, the flexible portion170of the distal-end shaft portion136is bent so that the expansion body21may deform to have a shape of the recess55according to the thickness of the biological tissue along the circumferential direction in the case where the thickness of the biological tissue around the puncture hole Hh varies in the circumferential direction.

As illustrated inFIG.16, a distal-end shaft portion137according to a sixth modified example in the second embodiment includes a flexible portion180in an intermediate portion in the axial direction, a distal-end rigid portion182on the side distal of the flexible portion180, and a proximal-end rigid portion184on the side proximal of the flexible portion180. The distal-end rigid portion182is formed of a hard outer pipe into which the pulling shaft33is inserted. The pulling shaft33includes the flexible portion180exposed to the side proximal of the distal-end rigid portion182in the axial direction, and the proximal-end rigid portion184disposed on the side proximal of the flexible portion180in the axial direction. That is, the proximal-end rigid portion184is formed on the pulling shaft33. As described above, the proximal-end rigid portion184may be formed on the pulling shaft33.

As illustrated inFIG.17, a distal-end shaft portion138according to a seventh modified example in the second embodiment includes a flexible portion190in an intermediate portion in the axial direction, a distal-end rigid portion192on the side distal of the flexible portion190, and a proximal-end rigid portion194on the side proximal of the flexible portion190. Both of the distal-end rigid portion192and the proximal-end rigid portion194are formed on the pulling shaft33, and a portion between the distal-end rigid portion192and the proximal-end rigid portion194is the flexible portion190. In this manner, both of the distal-end rigid portion192and the proximal-end rigid portion194may be formed on the pulling shaft33.

As illustrated inFIG.18, a distal-end shaft portion139according to an eighth modified example in the second embodiment includes a flexible portion200in an intermediate portion in the axial direction, a distal-end rigid portion202on the side distal of the flexible portion200, and a proximal-end rigid portion204on the side proximal of the flexible portion200. The flexible portion200, the distal-end rigid portion202, and the proximal-end rigid portion204are all formed on an outer pipe206into which the pulling shaft33is inserted. The outer pipe206is made of a relatively hard material, and the portion of the flexible portion200is made of a relatively flexible material. Alternatively, the outer pipe206may be entirely made of a relatively hard material, and a large number of slits or holes may be formed in the portion of the flexible portion200to form the flexible portion200that is easily bent. In this manner, the flexible portion200, the distal-end rigid portion202, and the proximal-end rigid portion204may all be formed on the outer pipe206.

As described above, the medical device10according to the second embodiment includes: the expansion body21that is expandable/contractible in the radial direction; the elongated shaft portion20including, in the distal end part, the proximal-end fixing portion131to which the proximal end of the expansion body21is fixed; the pulling shaft33that is disposed inside the shaft portion20, connected to the distal end part of the expansion body21by protruding from the distal end part of the shaft portion20, and slidable with respect to the shaft portion20; the distal-end shaft portion130that extends inside the expansion body21from the proximal end part to the distal end part of the expansion body21; and the electrode portion22disposed along the expansion body21, in which the expansion body21includes the recess55that is recessed radially inward and defines the reception space74configured to receive a biological tissue when the expansion body21is expanded, the recess55includes the bottom portion71located on the innermost side in the radial direction, the distal-side upright portion72extending radially outward from the distal end of the bottom portion71, and the proximal-side upright portion73extending radially outward from the proximal end of the bottom portion71, the electrode portion (energy transfer element22) is disposed along the distal-side upright portion72or the proximal-side upright portion73to face the reception space74, the pulling shaft33is configured to apply, to the expansion body21, a compressive force that makes compression along the axial center of the shaft portion20such that the distal-side upright portion72and the proximal-side upright portion73approach each other by sliding in the direction of the proximal end with respect to the shaft portion20, and in a state where the expansion body21is expanded, the distal-end shaft portion130includes the flexible portion160configured to be bent at the center in the axial direction, the distal-end rigid portion162disposed on the side distal of the flexible portion160in the axial direction, and the proximal-end rigid portion164disposed on the side proximal of the flexible portion160in the axial direction.

Furthermore, the method for forming a shunt according to the second embodiment forms, in an oval fossa, a shunt through which a right atrium communicates with a left atrium using the medical device10including the expansion body21that is expandable/contractible in the radial direction, the elongated shaft portion20including, in the distal end part, the proximal-end fixing portion131to which the proximal end of the expansion body21is fixed, the pulling shaft33that is disposed inside the shaft portion20, connected to the distal end part of the expansion body21by protruding from the distal end part of the shaft portion20, and slidable with respect to the shaft portion20, the distal-end shaft portion130that extends inside the expansion body21from the proximal end part to the distal end part of the expansion body21, and the electrode portion22disposed along the expansion body21, in which in a state where the expansion body21is expanded, the distal-end shaft portion130includes the flexible portion160configured to be bent at the center in the axial direction, the distal-end rigid portion162disposed on the side distal of the flexible portion160in the axial direction, and the proximal-end rigid portion164disposed on the side proximal of the flexible portion160in the axial direction, the method including: inserting the medical device10from an inferior vena cava into the right atrium; inserting the expansion body21in the contracted state into a hole formed in the oval fossa; expanding the expansion body21in the hole to dispose a biological tissue surrounding the hole in the reception space74defined by the recess55of the expansion body21including the bottom portion71located on the innermost side in the radial direction, the distal-side upright portion72extending radially outward from the distal end of the bottom portion71, and the proximal-side upright portion73extending radially outward from the proximal end of the bottom portion71; compressing, by sliding the pulling shaft33in the direction of the proximal end with respect to the shaft portion20, the expansion body21such that the distal-side upright portion72and the proximal-side upright portion73of the recess55approach each other to bend the flexible portion160according to thickness of the biological tissue surrounding the hole; bringing the electrode portion22disposed to face the recess55along the distal-side upright portion72or the proximal-side upright portion73of the recess55into contact with the biological tissue by bending of the flexible portion160; and cauterizing the biological tissue disposed in the reception space74using the electrode portion22in contact with the biological tissue to inhibit occlusion due to natural healing of the hole.

According to the medical device10and the method for forming a shunt according to the second embodiment configured as described above, it becomes possible to, when the thickness of the biological tissue to be in contact with the expansion body21varies along the circumferential direction, bend the distal-end shaft portion130at the portion of the flexible portion160depending on the thickness of the biological tissue to deform the expansion body21such that the recess55is brought into contact with each of portions of the biological tissue having larger and smaller thicknesses. As a result, it becomes possible to reliably bring the electrode portion (energy transfer element22) into contact with the biological tissue over the entire circumference.

The distal-end rigid portion162and the proximal-end rigid portion164may be formed of an outer pipe into which the pulling shaft33is inserted, and the flexible portion160may be formed of a portion of the pulling shaft33exposed from the distal-end rigid portion162and the proximal-end rigid portion164. With this arrangement, the rigidity of the distal-end rigid portion162and the proximal-end rigid portion164may be sufficiently secured.

The proximal-end rigid portion174may be formed of an outer pipe into which the pulling shaft33is inserted, and the pulling shaft33may include the flexible portion170exposed to the side distal of the proximal-end rigid portion174in the axial direction, and the distal-end rigid portion172disposed on the side distal of the flexible portion170in the axial direction. With this arrangement, it becomes possible to reduce the number of outer pipes to facilitate assembly.

The distal-end rigid portion182may be formed of an outer pipe into which the pulling shaft33is inserted, and the pulling shaft33may include the flexible portion180exposed to the side proximal of the distal-end rigid portion182in the axial direction, and the proximal-end rigid portion184disposed on the side proximal of the flexible portion180in the axial direction. With this arrangement, it becomes possible to reduce the number of outer pipes to facilitate assembly.

The distal-end shaft portion139may be formed of an outer pipe into which the pulling shaft33is inserted, and the distal-end shaft portion139may include the flexible portion200, the distal-end rigid portion202, and the proximal-end rigid portion204. With this arrangement, it becomes possible to reduce the number of outer pipes and eliminate the need to process the pulling shaft33.

The pulling shaft33may include the flexible portion190, the distal-end rigid portion192, and the proximal-end rigid portion194. With this arrangement, it becomes possible to form the distal-end rigid portion192and the proximal-end rigid portion194only with the pulling shaft33, whereby the number of parts may be further reduced.

Furthermore, the medical device10according to the first embodiment may include the distal-end shaft portions130,136,137,138, and139according to the second embodiment. For example, as in a ninth modified example illustrated inFIG.19, the medical device10according to the first embodiment includes the distal-end shaft portion130according to the second embodiment. The distal-end shaft portion130includes the proximal-end fixing portion131to which the proximal end of the expansion body21is fixed, and the distal-end fixing portion133to which the distal end of the expansion body21is fixed. The distal-end shaft portion130includes the flexible portion160, the distal-end rigid portion162disposed on the side distal of the flexible portion160in the axial direction, and the proximal-end rigid portion164disposed on the side proximal of the flexible portion160in the axial direction. With this arrangement, according to the medical device10and the method for forming a shunt in the ninth modified example, when the thickness of the biological tissue to be in contact with the expansion body21varies along the circumferential direction, the easy-to-deform portion (second strut64) deforms so that the reception space74at the position corresponding to the easy-to-deform portion in the circumferential direction increases and the distal-end shaft portion130is bent at the position of the flexible portion160depending on the thickness of the biological tissue, whereby the expansion body21may deform such that the recess55is brought into contact with each of portions of the biological tissue having larger and smaller thicknesses. With this arrangement, it becomes possible to more reliably bring the electrode portion22into contact with the biological tissue over the entire circumference.

The detailed description above describes embodiments of a medical device including an expansion body that expands in a living body and a method for forming a shunt. The invention is not limited, however, to the precise embodiments and variations described. Various changes, modifications and equivalents can be effected by one skilled in the art without departing from the spirit and scope of the invention as defined in the accompanying claims. It is expressly intended that all such changes, modifications and equivalents which fall within the scope of the claims are embraced by the claims.