Catheter with flow diverter and force sensor

A catheter probe comprises an insertion tube, and a distal end with a distal electrode, a force sensor to detect force on the distal electrode, and an irrigated electrode mounted on a coupling member of the force sensor, which has a tubular form surrounding a central space occupied by components, including force sensing coils. A fluid diverter that passes fluid to the proximal irrigated electrode is configured as an insert or an integrated projection of the coupling member, which configuration minimizes its space demand within the coupling member. Thus, the diameter of the distal end need not be increased. The fluid diverter has a proximal entry opening and a distal exit opening connected by a fluid passage with at least a radial branch and at least an axial branch. The irrigated electrode is mounted over the distal exit opening to receive fluid from the fluid passage.

FIELD OF INVENTION

The present invention relates generally to catheters having electrodes, and specifically to catheters wherein the electrodes are irrigated.

BACKGROUND OF INVENTION

Medical procedures involving ablation of the heart may be used to cure a variety of cardiac arrhythmia, as well as to manage atrial fibrillation. Such procedures are known in the art. Other medical procedures using ablation of body tissue, such as treating varicose veins, are also known in the art. The ablation energy for these procedures may be in the form of radio-frequency (RF) energy, which is supplied to the tissue via one or more electrodes of a catheter used for the procedures.

The application of the ablation energy to body tissue, if uncontrolled, may lead to an unwanted increase of temperature of the tissue. It is consequently important to control the temperature of the tissue during any medical procedure involving ablation. One method for control is to irrigate the tissue being ablated. However, irrigation requires components to deliver fluid from a proximal end of the catheter to its distal end. With catheter distal ends having diameters on the order of millimeters, space is often a primary constraint on the design and configuration of distal ends that provide for fluid delivery components. Moreover, with distal ends having tip and ring electrodes, such fluid delivery components must define fluid pathways that can provide axial flow and radial flow but occupy minimal space and avoid interfering with other functional aspects of the distal end, such as force sensing.

Documents incorporated by reference in the present patent application are to be considered an integral part of the application except that to the extent any terms are defined in these incorporated documents in a manner that conflicts with the definitions made explicitly or implicitly in the present specification, only the definitions in the present specification should be considered.

SUMMARY OF THE INVENTION

The present invention includes a probe, comprising an insertion tube, a distal electrode, and a proximal electrode. The probe includes a force sensor between the insertion tube and the distal electrode, the force sensor having a coupling member with a proximal portion with a central space and a proximal opening with a slot. The probe further includes a diverter situated in the slot, the diverter having a proximal entry opening and a distal exit opening connected by a fluid passage with a radial branch and an axial branch. A first tubing extends from a proximal end of the insertion tube to the proximal entry opening of the diverter, the first tubing configured to supply irrigation fluid to the fluid passage. Advantageously, the proximal electrode is mounted on the proximal portion of the coupling member, and is positioned over the distal exit opening to receive irrigation fluid delivered by the first tubing.

In some embodiments, the diverter is configured as an insert affixed in the slot.

In some embodiments, the coupling member has a tubular form with a convex outer surface, and the diverter has a corresponding convex outer surface.

In some embodiments, the diverter has an inner surface with a concavity to maximize space and to minimize interference with components occupying or passing through the central space of the coupling member.

In some embodiments, the diverter has an outer surface with an indent formation that extends around a peripheral edge of the outer surface, the indent formation engaging with the slot of the proximal portion of the coupling member.

In some embodiments, the proximal electrode is configured with side wall providing a space gap around the proximal portion, the space gap functioning as a reservoir for irrigation fluid.

In some embodiments, the probe includes an insulating sheath mounted on the proximal portion and the diverter, the sheath having a through-hole aligned with the distal exit opening of the diverter.

In some embodiments, a second tubing extending from a proximal end of the insertion tube to the distal electrode and through the central space of the coupling member, the second tubing configured to supply irrigation fluid to the distal electrode.

In some embodiments, a force sensing coil is housed in the central space without interference by the diverter.

In some embodiments, the diverter is positioned in substantially the same axial plane as the force sensing coil, but at a different azimuthal angle, to avoid interference with one or more force sensing coils housed in the central space.

The present invention is also directed to catheter probe, comprising an insertion tube, a distal electrode, and a proximal electrode. The probe includes a force sensor mounted on a distal end of the insertion tube, the force sensor having a coupling member with a distal portion, a proximal portion, a central space, the distal electrode distal of the coupling member, the proximal electrode mounted on the proximal portion, the force sensor configured to measure a force on the distal electrode, the force sensor having an integrated diverter with a fluid passage connecting a proximal entry opening and a distal exit opening, the diverter configured as a projection extending inwardly into the central space from a side wall of the proximal portion of the coupling member. The probe further includes a first tubing extending from a proximal end of the insertion tube to the proximal entry opening. Advantageously, the proximal electrode is positioned over the distal exit opening to receive irrigation fluid delivered by the first tubing.

In some embodiments, a second tubing extends from a proximal end of the insertion tube to the distal electrode and through the central space of the coupling member, the second tubing configured to supply irrigation fluid to the distal electrode.

In some embodiments, a transmitting coil is housed in the central space of the distal portion, one or more forcing sensing coils being responsive to the transmitting coil.

DETAILED DESCRIPTION OF THE INVENTION

Overview

An embodiment of the present invention provides a catheter probe which is typically used for a minimally invasive procedure such as ablation of cardiac tissue. The probe comprises an insertion tube, which, in order for it to be minimally invasive, usually has a small outer diameter of approximately 2 mm. At least one electrode, and typically two or more separate electrodes, are mounted on the distal end of the insertion tube (the distal end has approximately the same diameter as the insertion tube).

Mounted within the distal end is a force sensor, which measures the force on the distal end when the end contacts tissue. (Controlling the force enables tissue ablation to be performed more precisely.) The force sensor may have a tubular form that contacts an outer sheath of the insertion tube. The force sensor has a distal central opening, a proximal central opening, and typically defines a central space therebetween.

The one or more electrodes have respective sets of apertures, which are used to supply irrigation fluid to the electrodes and to body material in the region of the electrodes. Irrigation tubing supplies the irrigation fluid to the electrode apertures.

By using the “empty” region within the force sensor, including the proximal central opening and the central space, for the irrigation tubing and component(s), embodiments of the present invention use the available (small diameter) space at the distal end extremely efficiently. This efficient use of the space enables that the electrodes of the distal end to be irrigated during ablation, and also enables force during ablation to be measured, without requiring any increase in diameter of the catheter probe.

System Description

Reference is now made toFIG. 1, which is a schematic, pictorial illustration of a catheter probe ablating system10, and toFIG. 2which is a schematic cross-section of a distal end of a catheter probe14used in the system, according to embodiments of the present invention. In system10, probe14comprises an insertion tube16, which is inserted into a lumen18, such as a chamber of a heart20, of a subject22. The probe is used by an operator24of system10, during a procedure which typically includes performing ablation of body tissue26.

For intracardiac operation, insertion tube16and distal end12should generally have a very small outer diameter, typically of the order of 2-3 mm. Therefore, all of the internal components of catheter probe14, are also made as small and thin as possible and are arranged so as to, as much as possible, avoid damage due to small mechanical strains.

The functioning of system10is managed by a system controller30, comprising a processing unit32communicating with a memory34, wherein is stored software for operation of system10. Controller30is typically an industry-standard personal computer comprising a general-purpose computer processing unit. However, in some embodiments, at least some of the functions of the controller are performed using custom-designed hardware and software, such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). Controller30is typically managed by operator24using a pointing device and a graphic user interface (GUI)38, which enable the operator to set parameters of system10. GUI38typically also displays results of the procedure to the operator.

The software in memory34may be downloaded to the controller in electronic form, over a network, for example. Alternatively or additionally, the software may be provided on non-transitory tangible media, such as optical, magnetic, or electronic storage media.

One or more electrodes are mounted on distal end12. By way of example,FIG. 2illustrates three such electrodes: a first electrode110, a second electrode111, and a third electrode112, the electrodes being insulated from each other. The electrodes typically comprise thin metal layers formed over an insulating sheath46of tube16. The distal end may have other electrodes, insulated from each other and from electrodes110,111, and112, which for simplicity are not shown in the diagram. Electrode110, at the extremity of the distal end, by way of example is assumed to have the shape of a cup with a flat base, and is herein also referred to as the cup electrode. Cup electrode110typically has a thickness in a range from approximately 0.1 mm to approximately 0.2 mm.

Second electrode111is in the form of a ring, and is also referred to herein as ring electrode111. Ring electrode111is typically formed from metal having a similar thickness as the cup electrode. Third electrode112is an irrigated ring electrode. In the present disclosure, electrodes110,111and112, and other electrodes of the distal end, are also referred to herein collectively as electrodes115.

Electrodes115are connected to system controller30by conductors in tube16, not shown in the figures. As described below, at least one of the electrodes is used to ablate tissue26. In addition to being used for ablation, the electrodes typically perform other functions, as is known in the art; some of the other functions are described below. As necessary, when used for other functions, controller30may differentiate between the currents for the different functions by frequency multiplexing. For example, radio-frequency (RF) ablation power may be provided at frequencies of the order of hundreds of kHz, while position sensing frequencies may be at frequencies of the order of 1 kHz. A method of evaluating the position of distal end12using impedances measured with respect to the electrodes is disclosed in U.S. Patent Application 2010/0079158 to Bar-Tal et al., which is incorporated herein by reference.

System controller30comprises a force module48, an RF ablation module50, an irrigation module52, and a tracking module54. Processing unit32uses the force module to generate and measure signals supplied to, and received from, a force sensor58in distal end12in order to measure the magnitude and direction of the force on the distal end. The operation and construction of force sensor58is described in more detail below.

Processing unit32uses the ablation module to monitor and control ablation parameters such as the level of ablation power applied via the one or more electrodes115. The module also monitors and controls the duration of the ablation that is provided.

Typically, during ablation, heat is generated in the electrode or electrodes providing the ablation, as well as in the surrounding region. In order to dissipate the heat and to improve the efficiency of the ablation process, system10supplies irrigation fluid to distal end12. System10uses irrigation module52to monitor and control irrigation parameters, such as the rate of flow and the temperature of the irrigation fluid, as is described in more detail below.

Unit32uses tracking module54to monitor the location and orientation of the distal end relative to patient22. The monitoring may be implemented by any tracking method known in the art, such as one provided in the Carto3® system produced by Biosense Webster of Diamond Bar, Calif. Such a system uses radio-frequency (RF) magnetic transmitter and receiver elements external to patient22and within distal end12. Alternatively or additionally, the tracking may be implemented by measuring impedances between one or more electrodes, and patch electrodes attached to the skin of patient22, such as is also provided in the Carto3® system. For simplicity, elements specific to tracking and that are used by module54, such as the elements and patch electrodes referred to above, are not shown inFIG. 1.

As shown inFIG. 2, distal end12is connected to insertion tube16. The distal end has mounted upon it electrodes115, and force sensor58is mounted within the distal end. Aspects of a force sensor similar to force sensor58are described in U.S. Pat. No. 8,357,152, to Govari et al., issued Jan. 22, 2013, and in U.S. Patent Application 2011/0130648, to Beeckler et al., filed Nov. 30, 2009, both of whose disclosures are incorporated herein by reference.

FIG. 2shows a schematic, sectional view of force sensor58. Sensor58comprises a resilient coupling member60, which forms a spring joint62between two ends of the coupling member. By way of example, coupling member60is assumed to be formed in two parts or having two portions, a first part or portion64and a second part or portion66, the two parts being fixedly joined together. The two parts of coupling member60are generally tubular, and are joined so that the coupling member also has a tubular form with a central opening. Although there is no necessity that coupling member60be formed of two parts, the two-part implementation simplifies assembly of elements comprised in the force sensor, as well as of other elements mounted in the distal end, into the member.

Coupling member60typically has one or more helices70cut in a portion of the length of first portion64of the member, so that the member behaves as a spring. In an embodiment described herein, and illustrated inFIG. 2, helices70are formed as two intertwined helices, a first cut helix72and a second cut helix74, which are also referred to herein as a double helix. However, coupling member60may have any positive integral number of helices, and those having ordinary skill in the art will be able to adapt the present description without undue experimentation to encompass numbers of helices other than two. Alternatively, the coupling member may comprise a coil spring or any other suitable sort of resilient component with similar flexibility and strength characteristics to those generated by the one or more tubular helical cuts, referred to above.

Coupling member60is mounted within and covered by sheath46, which is typically formed from flexible plastic material. Coupling member60typically has an outer diameter that is approximately equal to the inner diameter of sheath46. Such a configuration, having the outer diameter of the coupling member to be as large as possible, increases the sensitivity of force sensor58. In addition, and as explained below, the relatively large diameter of the tubular coupling member, and its relatively thin walls, provide a central space61enclosed within the coupling member which is occupied by other elements, described below, in the distal end.

When catheter probe14is used, for example, in ablating endocardial tissue by delivering RF electrical energy through electrodes115, considerable heat is generated in the area of distal end12. For this reason, it is desirable that sheath46comprises a heat-resistant plastic material, such as polyurethane, whose shape and elasticity are not substantially affected by exposure to the heat.

Within force sensor58, typically within the central space61of the coupling member60, a joint sensing assembly, comprising coils76,78,80and82, provides accurate reading of any dimensional change in joint62, including axial displacement and angular deflection of the joint. These coils are one type of magnetic transducer that may be used in embodiments of the present invention. A “magnetic transducer,” in the context of the present patent application and in the claims, means a device that generates a magnetic field in response to an applied electrical current and/or outputs an electrical signal in response to an applied magnetic field. Although the embodiments described herein use coils as magnetic transducers, other types of magnetic transducers may be used in alternative embodiments, as will be apparent to those skilled in the art.

The coils in the sensing assembly are divided between two subassemblies on opposite sides of joint62: one subassembly comprises coil82, which is driven by a current, via a cable (not shown) from controller30and force module48, to generate a magnetic field. This field is received by a second subassembly, comprising coils76,78and80, which are located in a section of the distal end that is spaced axially apart from coil82. The term “axial,” as used in the context of the present patent application and in the claims, refers to the direction of a longitudinal axis of symmetry84of distal end12. An axial plane is a plane perpendicular to this longitudinal axis, and an axial section is a portion of the catheter contained between two axial planes. Coil82typically has an axis of symmetry generally parallel to and coincident with axis84.

Coils76,78and80are fixed in distal end12at different radial locations. (The term “radial” refers to coordinates relative to the axis84.) Specifically, in this embodiment, coils76,78and80are all located in the same axial plane at different azimuthal angles about the catheter axis, and have respective axes of symmetry generally parallel to axis84. For example, the three coils may be spaced azimuthally 120° apart at the same radial distance from the axis.

Coils76,78and80generate electrical signals in response to the magnetic field transmitted by coil82. These signals are conveyed by a cable (not shown) to controller30, which uses force module48to process the signals in order to measure the displacement of joint62parallel to axis84, as well as to measure the angular deflection of the joint from the axis. From the measured displacement and deflection, controller30is able to evaluate, typically using a previously determined calibration table stored in force module48, a magnitude and a direction of the force on joint62.

Controller30uses tracking module54to measure the location and orientation of distal end12. The method of measurement may be by any convenient process known in the art. In one embodiment, magnetic fields generated external to patient22create electric signals in elements in the distal end, and controller30uses the electric signal levels to evaluate the distal end location and orientation. Alternatively, the magnetic fields may be generated in the distal end, and the electrical signals created by the fields may be measured external to patient22. For simplicity, the elements in distal end12that are used to track the distal end are not shown inFIG. 2. However, where such elements comprise coils, at least some of coils76,78,80, and82may be used as the tracking elements required in the distal end, in addition to their use as elements of force sensor58.

At least some of electrodes115are configured to have small irrigation apertures. The apertures typically have diameters in an approximate range 0.1-0.2 mm. In the embodiment described herein cup electrode110and irrigated ring electrode112have respective sets of irrigation apertures86and90. The irrigation fluid for the apertures is supplied by irrigation module52, which uses tubing92to transfer the fluid to the sets of irrigation apertures.

The irrigation fluid is typically normal saline solution, and the rate of flow of the fluid, controlled by module52, is typically in the range of approximately 10-20 cc/minute, but may be higher or lower than this range.

Tubing92delivers fluid to the distal end of the probe. A distal end of the tubing92is received in a flow diverter150configured in the second (or proximal) portion66of the coupling member60. The fluid is routed to the electrodes by passing through the diverter150which is advantageously situated in and through the central space61of the coupling member60and thus makes no extra demands on the dimensional requirements, particularly the diameter, of the distal end, other than those required for force sensor58.

In this embodiment, flow diverter150may be positioned within or near the axial plane of elliptical coils142and144. For example, flow diverter150and elliptical coils142and144may be spaced radially about catheter axis84at different azimuthal angles. This configuration allows flow diverter150, and therefore, irrigated ring electrode112to be positioned relatively distally without interfering with the functionality of force sensor58. It may be desirable to reduce the distance between cup electrode110and ring electrode112to provide efficient ablation of the tissue between the electrodes. At the same time, it may also be desirable to position ring electrode112proximal to spring joint122so as to reduce the distance between cup electrode110and force sensor58, so that force sensor58may provide more accurate indication of the position of cup electrode110.

In some embodiments, the diverter150has an elongated body between a distal end151and a proximal end152, as shown inFIG. 3andFIG. 4. An outer surface160of the diverter body has a convexity with a curvature generally corresponding or matching the outer curvature of the tubular form of the coupling member60, including the proximal portion66. On the outer surface160, a step or indent formation162extends around a peripheral edge of the outer surface. The body has tapered radial sides166and an inner surface164with a concavity.

The diverter body has a fluid passage153that connects a proximal entry opening155, and a distal exit opening156. The fluid passage153includes a proximal axial branch distal of the entry opening155and a distal radial branch proximal of the exit opening155. Thus, fluid entering the diverter through the entry opening155is initially guided in an axial direction A, following by a radial direction R before exiting the diverter through the exit opening156in the outer surface160. It is understood that the fluid passage153may have any suitable cross-sectional shape, including for example, circular, rectangular, or polygonal.

The diverter150is positioned in a sidewall67of the proximal portion66of the coupling member60. As shown inFIG. 5andFIG. 6, a proximal end of the proximal portion66includes a longitudinal slot91defined by an elongated U-shaped edge95with a proximal opening that is coextensive with the proximal end152of the diverter150when inserted in the slot91. The diverter150is inserted into the slot91by sliding engagement between the peripheral indent formation162and the U-shaped edge95. The peripheral indent formation162has a rounded distal portion170that corresponds with the U-shaped edge95. The outer surface160of the diverter150is generally flush or even with an outer surface of sidewall of the proximal portion66. The diverter150may be affixed in the slot91by adhesive applied between engaged surfaces of the peripheral indent formation162and the U-shaped edge95, which also seals the engaged surfaces. The diverter150is constructed of any suitable material, including, for example, PEEK.

As shown in the embodiment ofFIG. 3,FIG. 5andFIG. 6, a distal end of the tubing92is inserted and received in the entry opening155at the proximal end152of the diverter150. Where the distal end includes a tubular component165, for example, a guide wire lumen, the inner surface164(with its concavity C) of the diverter150generally conforms to a convex outer surface of the tubular component165. The tapered sides166minimize the demand on space within the proximal portion66. For example, the adjacent tapered side does not physically interfere with elliptic coil142. As shown inFIG. 6, the diverter150leaves sufficient room within the central space61to accommodate another elliptical coil144, and at least another tubing145, for example, with a lumen146to pass cables for receiving coils76,78and80, transmitting coil82, and/or elliptic coils142and144. Notably, lead wire180for cup electrode112may be wound on an outer surface of the tubing145, under a protective nonconductive sheath182.

As shown inFIG. 5, the ring electrode112with apertures90is mounted over the proximal portion66of the coupling member60, in particular, over the exit opening156. The sheath46is positioned between the proximal portion66and the ring electrode112to prevent electrical shorting. The sheath has a through-hole aligned with the exit opening156.

In use, the diverter150receives fluid passed from the tubing92into the entry opening155which travels through the fluid passage153axially and then radially to exit from the exit opening156of the diverter150and the through-hole176of the sheath46. The fluid then enters a sealed annular space gap G or reservoir provided between the proximal portion66(and the sleeve74), and a sidewall114of the ring electrode112, before exiting the ring electrode112via the apertures90.

In other embodiments, a proximal portion266of a coupling member has an integrated flow diverter250, as shown inFIG. 7andFIG. 8. The diverter250is formed in a portion of a radial projection or rib262extending inwardly into central space261of the proximal portion266. The radial projection262spans longitudinally, along all or a portion of the length of the proximal portion266. Formed in a proximal portion of the radial projection262, a fluid passage290is defined by sidewalls, including two radial sidewalls280and281, an inner sidewall282, a distal end sidewall283which may be at a predetermined distance from the distal end of the radial projection262or a distal end of the proximal portion266. These sidewalls and a sidewall portion267of the proximal portion266together define and surround the fluid passage290, which extends from a proximal entry opening255at proximal opening263to a distal exit opening256proximal to the distal end of the proximal portion266. The diverter250is thus integral with the proximal portion266. In that regard, the proximal portion266and the integrated flow diverter250are formed from a single body, of a common material, for example, a superelastic alloy, such as nickel titanium (Nitinol).

The fluid passage290includes at least an axial branch291and radial branch292, as shown inFIG. 8. An inner surface284of the inner sidewall282has a concavity, as shown inFIG. 7, which can conform to a tubular component within the central space261of the portion266

It is understood that the fluid passage290or190may follow any suitable pattern, including combinations of one or more axial or generally axial branches with one or more radial or generally radial branches, between one or more entry openings and one or more exit openings, with dedicated tubing supplying fluid to each entry opening. For example, the fluid passage may include a Y passage having a main axial branch and additional offset branches. InFIG. 9, a diverter450A of proximal portion466A has an entry opening455, a proximal exit opening456P, a distal exit opening456D, a fluid passage an axial branch, a proximal radial branch, and a distal radial branch. InFIG. 10, a diverter450B of proximal portion466B has a proximal entry opening455, a proximal exit opening456A, two distal exit openings456B and456C, a fluid passage with an on-axis axial branch and two off-axis axial branch, and three radial branches. InFIG. 11, diverter450C of proximal portion466C has two separate and independent entry openings455A and455B, each having a fluid passage with a respective axial branch, radial branch and exit opening456A and456B.

For any of the foregoing embodiments, controller30ofFIG. 1may set the rate of flow to the individual electrodes according to the function performed by the electrode. For example, if an electrode is being used for ablation, controller30may increase the flow rate through the electrode compared to when the electrode is not being used for ablation. Alternatively or additionally, controller30may alter the flow rate to a particular electrode according to a value of a parameter measured by a sensor in the distal end. Such parameters include the magnitude of the force measured by force sensor58, as well as the direction of the force measured by the force sensor. Other sensors that the controller may use to alter the flow rate include a temperature sensor in the distal end.

Typically, controller30and irrigation module52maintain a minimum rate of flow of irrigation fluid to each electrode, to prevent blood entering the irrigation apertures of the electrodes. In some embodiments, rather than having irrigation fluid supplied to the separate electrodes via a common tubing, separate irrigation tubes to each electrode are run from module52through probe14. As shown inFIG. 2, distal cup electrode110is fed by dedicated irrigation tube126.

The preceding description has been presented with reference to certain exemplary embodiments of the invention. Workers skilled in the art and technology to which this invention pertains will appreciate that alterations and changes to the described structure may be practiced without meaningfully departing from the principal, spirit and scope of this invention, and that the drawings are not necessarily to scale. Moreover, it is understood that any one feature of an embodiment may be used in lieu of or in addition to feature(s) of other embodiments. Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and illustrated in the accompanying drawings. Rather, it should be read as consistent with and as support for the following claims which are to have their fullest and fairest scope.