Support strip-based ablation catheter with retainer feature

Abstract

An ablation catheter includes a tubular shaft having a proximal portion and a distal end and an electrode assembly extending from the distal end of the shaft. The electrode assembly includes a plurality of support bars, each having a support bar proximal portion secured to the shaft and an opposing support bar distal portion. Each support strip includes an electrically conductive support member partially disposed within an insulating member. The support member has a proximal end portion disposed within the insulating member and a distal end portion extending distally of the insulating member and terminating at a distal end of the support member. A plurality of sensing electrodes are disposed along each of the support strips. The support bar retainer is mechanically engaged with at least one of the proximal portion and the distal portion of the support bar.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 578,529, filed August 24, 2023, entitled “SPLINE-BASED ABLATION CATHETERHAVING RETAINER FEATURE,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to medical systems and methods for ablating tissue in a patient's body. More specifically, this disclosure relates to medical systems and methods for ablating tissue by electroporation. Background Technology

[0004] Ablation procedures are used to treat many different conditions in patients. Ablation can be used to treat arrhythmias, benign tumors, cancerous tumors, and to control bleeding during surgery. Typically, ablation is performed using thermal ablation techniques, including radiofrequency (RF) ablation and cryoablation. In RF ablation, a probe is inserted into the patient's body, and radiofrequency waves are delivered through the probe to the surrounding tissue. The radiofrequency waves generate heat, destroying the surrounding tissue and burning blood vessels. In cryoablation, a hollow needle or cryoprobe is inserted into the patient's body, and a cold, heat-conducting fluid circulates through the probe to freeze and kill the surrounding tissue. Both RF ablation and cryoablation techniques indiscriminately kill tissue through cell necrosis, which may damage or otherwise kill healthy tissue, such as tissue in the esophagus, phrenic nerve cells, and tissue in the coronary arteries.

[0005] Another ablation technique uses electroporation. In electroporation, or electroosmosis, an electric field is applied to the cells to increase the permeability of the cell membrane. Electroporation can be reversible or irreversible, depending on the strength of the electric field. If electroporation is reversible, the increased permeability of the cell membrane can be used to introduce chemicals, drugs, and / or DNA into the cells before they heal and recover. If electroporation is irreversible, the affected cells are killed through apoptosis.

[0006] Irreversible electroporation can be used as a non-thermal ablation technique. In irreversible electroporation, a series of short, high-voltage pulses are used to generate a strong electric field sufficient to kill cells through apoptosis. In the ablation of cardiac tissue, irreversible electroporation may be a safe and effective alternative to thermal ablation techniques such as RF ablation and cryoablation. Irreversible electroporation kills the target tissue, such as myocardial tissue, by using the intensity and duration of an electric field that kills the target tissue without permanently damaging other cells or tissues, such as non-target myocardial tissue, erythrocytes, vascular smooth muscle tissue, endothelial tissue, and nerve cells. Planning an irreversible electroporation ablation procedure can be difficult due to the lack of real-time visualization or data indicating which tissues have been affected by irreversible electroporation (as opposed to reversible electroporation, where tissue recovery can occur within minutes, hours, or days after ablation). Summary of the Invention

[0007] Example 1 is a catheter for ablation of cardiac tissue via irreversible electroporation. The catheter includes a tubular shaft having a proximal portion and a distal end; an electrode assembly extending from the distal end of the shaft, the electrode assembly including a plurality of support bars, each support bar having a proximal portion fixed to the shaft and an opposing distal portion. Each support bar includes: a conductive support member having a proximal portion of the support member coupled to the distal end of the shaft and a distal portion of the support member terminated at the distal end of the support member, wherein each conductive support member is configured to operate as a first ablation electrode, the first ablation electrode being configured to generate an electric field when a pulse waveform is delivered to each support member. An electrically insulating member covers the proximal portion of the support member, the insulating member having a proximal portion of the insulating member coupled to the distal end of the shaft; and a plurality of sensing electrodes disposed along the insulating member. A support bar retainer mechanically engages with at least one of the distal or proximal portions of the support member of each of the plurality of support bars, the support bar retainer being adapted to mechanically support the support bar.

[0008] Example 2 is the conduit described in Example 1, wherein the support bar retainer includes a distal support bar retainer that is mechanically coupled to the distal end of the support member of each of the plurality of support bars, thereby mechanically connecting the distal portions of the support bars together.

[0009] In Example 3, according to the catheter described in Example 2, the distal support bar retainer is conductive and electrically connected to one or more support members, and is configured to form part of the first ablation electrode.

[0010] In Example 4, according to the catheter described in Example 2, the distal support bar retainer is configured to operate as a distal sensing electrode.

[0011] In Example 5, the distal support bar retainer is disposed at the distal end of the electrode assembly in the catheter according to any one of Examples 2-4.

[0012] In Example 6, the distal support bar retainer of the catheter according to any one of Examples 2-5 is a conductive ball.

[0013] In Example 7, the catheter according to any one of Examples 5-6, wherein the distal support bar retainer includes a first piece located proximal to the distal end, the first piece being mechanically coupled to a second piece located distal to the distal end.

[0014] In Example 8, the catheter according to any one of claims 1-7, wherein the first ablation electrode is configured as a unipolar ablation electrode.

[0015] In Example 9, the catheter according to any one of Examples 1-8 further includes an axial electrode disposed on the shaft near its distal end.

[0016] In Example 10, according to the catheter described in Example 9, the first ablation electrode and the axial electrode are configured to form an electrode pair for bipolar ablation.

[0017] In Example 11, in the catheter according to any one of Examples 1-10, at least one of the support strip sensing electrodes is configured to operate as a second ablation electrode.

[0018] In Example 12, in the catheter according to any one of claims 1-10, at least one of the support strip sensing electrodes is configured to operate as a second ablation electrode.

[0019] In Example 13, the catheter according to any one of Examples 1-12, the support bar retainer includes a proximal support bar retainer that mechanically abuts against the proximal portion of the support member of each of the plurality of support bars, thereby spacing the proximal portions of the support bars apart in both expanded and contracted states.

[0020] In Example 14, according to the catheter described in Example 13, a proximal support bar retainer is coupled to the distal end of the shaft and extends from the distal end of the shaft into the internal space formed by the electrode assembly.

[0021] In Example 15, the proximal support bar retainer is integral with the distal end of the shaft, according to the catheter described in Example 13.

[0022] Example 16 is a catheter for ablation of cardiac tissue via irreversible electroporation, the catheter comprising: a tubular shaft having a proximal portion and a distal end; an electrode assembly extending from the distal end of the shaft, the electrode assembly comprising a plurality of support bars, each support bar having a proximal support bar portion fixed to the shaft and an opposing distal support bar portion, each support bar comprising: a conductive support member having a support member proximal portion coupled to the distal end of the shaft and a support member distal portion terminated at the distal end of the support member, wherein each conductive support member is configured to operate as a first ablation electrode, the first ablation electrode being configured to generate an electric field when a pulse waveform is delivered to each support member; and an electrically insulating member covering the proximal portion of the support member, the insulating member having an insulating member proximal portion coupled to the distal end of the shaft; and a plurality of sensing electrodes disposed along the insulating member; and a support bar retainer mechanically engaging at least one of the distal or proximal support bar portions of each of the plurality of support bars, the support bar retainer being adapted to mechanically support the support bar.

[0023] In Example 17, the conduit according to Example 16, wherein the support bar retainer includes a distal support bar retainer that is mechanically coupled to the distal end of the support member of each of the plurality of support bars, thereby mechanically connecting the distal portions of the support bars together.

[0024] In Example 18, the distal support bar retainer of the catheter according to Example 17 is conductive and electrically connected to one or more of the support members, and is configured to form part of the first ablation electrode.

[0025] In Example 19, according to the catheter described in Example 17, the distal support bar retainer is configured to operate as a distal sensing electrode.

[0026] In Example 20, the conduit according to Example 19 is provided with a distal support bar retainer at the distal end of the electrode assembly.

[0027] In Example 21, the catheter according to Example 20 is provided, wherein the distal support bar retainer is a conductive ball.

[0028] In Example 22, according to the catheter described in Example 20, the distal support bar retainer includes a first piece located proximal to the distal end, which is mechanically coupled to a second piece located distal to the distal end.

[0029] In Example 23, according to the catheter described in Example 16, the first ablation electrode is configured for unipolar ablation.

[0030] In Example 24, the conduit according to Example 16 further includes an axial electrode disposed on the shaft near its distal end.

[0031] In Example 25, according to the catheter described in Example 24, the first ablation electrode and the axial electrode are configured to form an electrode pair for bipolar ablation.

[0032] In Example 26, according to the catheter described in Example 16, at least one of the support strip sensing electrodes is configured to operate as a second ablation electrode.

[0033] In Example 27, according to the catheter described in Example 26, at least one of the support bar sensing electrodes and the first ablation electrode are configured to operate together as a unipolar ablation electrode.

[0034] In Example 28, according to the catheter described in Example 16, the support bar retainer includes a proximal support bar retainer that mechanically abuts against the proximal portion of the support member of each of the plurality of support bars, thereby spacing the proximal portions of the support bars apart in both expanded and contracted states.

[0035] In Example 29, according to the catheter described in Example 28, a proximal support bar retainer is coupled to the distal end of the shaft and extends from the distal end of the shaft into the internal space formed by the electrode assembly.

[0036] In Example 30, the catheter according to Example 28 has a proximal support bar retainer that is integral with the distal end of the shaft.

[0037] Example 31 is a catheter for ablation of cardiac tissue via irreversible electroporation, the catheter comprising: a tubular shaft having a proximal portion and a distal end; an electrode assembly extending from the distal end of the shaft, the electrode assembly including a plurality of support strips, each support strip having a proximal portion of the support strip fixed to the shaft and an opposing distal portion of the support strip; an electrically insulating member covering the proximal portion of the support strips, the insulating member having a proximal portion of the insulating member coupled to the distal end of the shaft; a plurality of sensing electrodes disposed along the insulating member; and a support strip retainer mechanically engaged with at least one of the proximal and distal portions of the support strips, the support strip retainer being adapted to mechanically support the support strips.

[0038] In Example 32, according to the conduit of Example 31, the support bar retainer includes a distal support bar retainer that is mechanically coupled to the distal end of each distal portion of the support bar, thereby mechanically coupling the distal portions of the support bar.

[0039] In Example 33, the distal support bar retainer of the catheter according to Example 32 is conductive and configured to form part of the first ablation electrode.

[0040] In Example 34, the distal support bar retainer is a conductive ball, according to the catheter described in Example 33.

[0041] In Example 35, according to the conduit of Example 31, a support bar retainer is coupled to the distal end of the shaft and extends from the distal end of the shaft into the internal space formed by the electrode assembly.

[0042] While several embodiments have been disclosed, other embodiments of this disclosure will become apparent to those skilled in the art from the following detailed description, which illustrates and describes illustrative embodiments of the invention. Therefore, the drawings and detailed description are to be considered illustrative in nature and not restrictive. Attached Figure Description

[0043] Figure 1 This is a schematic diagram illustrating an exemplary clinical setup for treating a patient and treating the patient's heart using an electrophysiological system according to embodiments of the subject matter of this disclosure.

[0044] Figure 2A It is possible to be with Figure 1 A side view of an example electroporation catheter used in conjunction with an example electrophysiological system.

[0045] Figure 2B yes Figure 2A A perspective view of an example catheter.

[0046] Figure 3 It is possible to be with Figure 1 A perspective view of a portion of the features of an example catheter used in an example electrophysiological system.

[0047] Figure 4 It is possible to be with Figure 1 A perspective view of an example electroporation catheter used in conjunction with an example electrophysiological system, including those that can also be incorporated into... Figure 2A-2B Features of an example electroporation catheter.

[0048] While this disclosure may have various modifications and alternatives, specific embodiments are illustrated by way of example in the accompanying drawings and are described in detail below. However, this disclosure does not limit the invention to the specific embodiments described. Rather, this disclosure is intended to cover all modifications, equivalents, and alternatives that fall within the scope of this disclosure as defined by the appended claims. Detailed Implementation

[0049] To facilitate understanding of the principles of this disclosure, reference is now made to the examples illustrated in the accompanying drawings, which are described below. The examples shown herein are not intended to be exhaustive or to limit this disclosure to the precise forms disclosed in the following detailed description. Rather, these exemplary embodiments were chosen and described to enable those skilled in the art to use their teachings. Applying multiple (e.g., all) features from a given example to all examples does not exceed the scope of this disclosure. Therefore, no single figure should be construed as having any dependency or requirement on any individual component or combination of components shown therein. Furthermore, in the examples, various components depicted in a given figure may be integrated with various other components (and / or components not shown) depicted therein, all of which are considered to be within the scope of this disclosure.

[0050] The terms “connection,” “joining,” “attachment,” and their variations are used to include arrangements in which two or more components are in direct physical contact with each other and arrangements in which two or more components are not in direct contact with each other (e.g., components are “connected” via at least a third component) but still cooperate or interact with each other.

[0051] Throughout this disclosure and the claims, numerical terms such as “first” and “second” are used to refer to different parts or features. This use is not intended to indicate an order of parts or features. Rather, numerical terms are used to help the reader identify the referenced parts or features and should not be narrowly interpreted as a specific order in which the parts or features are arranged.

[0052] Figure 1 This is a schematic diagram illustrating an exemplary clinical setup 10 for treating a patient 20 and the heart 30 of the patient 20 using an electrophysiology system 50 according to embodiments of the subject matter of this disclosure. The electrophysiology system 50 includes an electroporation catheter system 60 and an electroanatomical mapping (EAM) system 70, which includes a localization field generator 80, a mapping and guidance controller 90, and a display 92. Furthermore, the clinical setup 10 includes additional devices such as an imaging device 94 (represented by a C-arm) and various controller elements, such as a foot controller 96, configured to allow an operator to control various aspects of the electrophysiology system 50. As those skilled in the art will understand, the clinical setup 10 may have… Figure 1 Other components and their arrangement not shown.

[0053] The electroporation catheter system 60 includes an electroporation catheter 100 having a proximal portion 102 and a distal portion 105, an insertion sheath 110, and an electroporation console 130. Furthermore, the electroporation catheter system 60 includes various connecting elements, such as cables, umbilical cables, etc., for functionally connecting the components of the electroporation catheter system 60 to each other and to components of the EAM system 70. This arrangement of the connecting elements is not particularly important to this disclosure, and those skilled in the art will recognize that the various components described herein can be interconnected in a variety of ways.

[0054] In one embodiment, the introduction sheath 110 is operable to provide a delivery conduit through which the electroporation catheter 100 (partially its distal portion 105) can be deployed to a specific target site within the patient's heart 30.

[0055] In one embodiment, the electroporation catheter system 60 is configured to deliver electric field energy to targeted tissue in the patient's heart 30 to induce tissue cell apoptosis, thereby preventing the tissue from conducting electrical signals.

[0056] The electroporation console 130 is configured to control functional aspects of the electroporation catheter system 60. In embodiments, the electroporation console 130 includes one or more controllers, microprocessors, and / or computers that execute code from memory to control and / or perform functional aspects of the electroporation catheter system 60. In embodiments, the memory may be part of one or more controllers, microprocessors, and / or computers, and / or a portion of a memory capacity accessible via a network such as the World Wide Web. In embodiments, the electroporation console 130 includes pulse generator hardware, software, and / or firmware configured to generate electrical pulses of predetermined waveforms that can be delivered to electrodes on the electroporation catheter 100 to generate an electric field sufficient to achieve the desired clinical effect, particularly by irreversibly ablating targeted tissue via electroporation. In embodiments, the electroporation console 130 may deliver pulse waveforms to the electroporation catheter 100 in unipolar or bipolar operating modes, which will be described in further detail herein.

[0057] The EAM system 70 is operable to track the location of various functional components of the electroporation catheter system 60 and generate high-fidelity three-dimensional anatomical and electroanatomical mappings of the chambers of interest. In an embodiment, the EAM system 70 may be the RHYTHMIA™ HDx mapping system sold by Boston Scientific. Furthermore, in an embodiment, the mapping and guidance controller 90 of the EAM system 70 includes one or more controllers, microprocessors, and / or computers that execute code from memory to control and / or perform functional aspects of the EAM system 70, wherein in an embodiment, the memory may be part of one or more controllers, microprocessors, and / or computers, and / or a portion of memory capacity accessible via a network such as the World Wide Web.

[0058] As those skilled in the art will understand, Figure 1 The description of the electrophysiological system 50 shown is intended to provide a general overview of the various components of the system 50 and is in no way intended to imply that this disclosure is limited to any collection of components or arrangement of components. For example, those skilled in the art will readily recognize that additional hardware components (e.g., adapter boxes, workstations, etc.) can and may be included in the electrophysiological system 50.

[0059] The EAM system 70 generates a positioning field via a field generator 80 to define a positioning space around the heart 30, and outputs are generated by one or more position sensors or sensing elements on a tracking device (e.g., an electroporation catheter 100). These outputs can be processed by a mapping and guidance controller 90 to track the positions of the sensors within the positioning space, and thus the positions of the corresponding devices. In the illustrated embodiment, device tracking is achieved using magnetic tracking technology, where the field generator 80 is a magnetic field generator that generates a magnetic field defining the positioning space, and the position sensors on the tracked devices are magnetic field sensors.

[0060] In other embodiments, impedance tracking methods can be used to track the position of various devices. In such embodiments, the positioning field is an electric field generated, for example, by an external field generator (e.g., surface electrodes), an in vivo or intracardiac device (e.g., an intracardiac catheter), or both. In these embodiments, position sensing elements can form electrodes on the tracked device, generating outputs received and processed by the mapping and guidance controller 90 to track the positions of various position sensing electrodes within the positioning space.

[0061] In this embodiment, the EAM system 70 is equipped with magnetic and impedance tracking capabilities. In such embodiments, impedance tracking accuracy can be enhanced in some cases by first creating a mapping of the electric field induced by an electric field generator within the chamber of interest using a probe equipped with a magnetic position sensor; this can be achieved using the aforementioned RHYTHMIA HDx™ mapping system. An exemplary probe is the INTELLAMAP ORION™ mapping catheter, sold by Boston Scientific.

[0062] Regardless of the tracking method used, the EAM system 70 utilizes the location information of various tracked devices and cardiac electrical activity acquired by, for example, an electroporation catheter 100 or another catheter or probe equipped with sensing electrodes to generate and display detailed three-dimensional geometric anatomical mappings or representations of cardiac chambers and electroanatomical mappings via a display 92, wherein the cardiac electrical activity of interest is superimposed on the geometric anatomical mappings. Furthermore, the EAM system 70 can generate graphical representations of various tracked devices within the geometric anatomical mappings and / or electroanatomical mappings.

[0063] Embodiments of this disclosure provide systems, apparatus, and methods for selectively and rapidly applying pulsed electric fields to ablate tissue via irreversible electroporation. Generally, the systems, apparatus, and methods described herein can be used to generate large electric field amplitudes in desired regions of interest and reduce electric field peaks elsewhere to minimize unwanted tissue damage and arcing. The irreversible electroporation systems described herein may include a signal generator and processor configured to apply one or more voltage pulse waveforms to a selected set of electrodes of an ablation apparatus to deliver energy to the region of interest (e.g., ablation energy for a set of tissues in the pulmonary vein ostium or sinus). The pulse waveforms disclosed herein can aid in the treatment of various cardiac arrhythmias, such as atrial fibrillation. To deliver the pulse waveforms generated by the signal generator, one or more electrodes of the ablation apparatus may have insulated leads configured to maintain potentials in the range of several hundred to several thousand volts. The electrodes may be independently addressable, such that each electrode can be controlled (e.g., delivered energy) independently of any other electrode in the apparatus. In this way, electrodes can work together to deliver different energy waveforms with different timings to the tissue via electroporation.

[0064] The pulse waveforms disclosed herein for energy delivery in electroporation can enhance the safety, efficiency, and effectiveness of energy delivery to tissue by reducing the electric field threshold associated with irreversible electroporation, thus resulting in more effective ablation lesions while reducing the total energy delivered. In some embodiments, the voltage pulse waveforms disclosed herein may be hierarchical and have a nested structure. For example, the pulse waveforms may include hierarchical groupings of pulses with associated time scales. In some embodiments, the methods, systems, and apparatuses disclosed herein may include one or more of the methods, systems, and apparatuses described in International Application No. PCT / US2016 / 057664, filed October 19, 2016, entitled “SYSTEMS, APPARATUSES AND METHODS FOR DELIVERY OF ABLATIVE ENERGY TO TISSUE,” the contents of which are incorporated herein by reference in their entirety.

[0065] Figure 2A and Figure 2B Multiple views are shown of an embodiment of an electroporation catheter 200 for ablation of cardiac tissue, or the distal region 205 of the electroporation catheter 200, which may be an example of catheter 100 and used in conjunction with an electrophysiological system 50. The electroporation catheter 200 includes a tubular shaft 202 defining a longitudinal axis A and having a distal end 204 of shaft 202 and a proximal end of the opposing shaft. The longitudinal axis A is represented as a line passing through the centroid of the cross-section of shaft 202. The distal region 205 of the catheter 200 is configured to be deployed close to target tissue, such as in the chambers of a patient's heart. An expandable electrode assembly 210 is coupled to the distal end 204 of the shaft and configured to generate an electric field. In one example, the electric field generates irreversible electroporation in selected cardiac tissue. The electrode assembly 210 is switchable between a constricted state and an expanded state. In the expanded state, the electrode assembly 210 includes a maximum radial dimension greater than the maximum radial dimension of the distal end 204 of the elongated shaft 202.

[0066] The electrode assembly 210 includes a plurality of longitudinally extending support bars 212 that form a spherical basket 214 in an expanded state. A sphere (as used herein to define the shape of the electrode assembly in an expanded state) includes a sphere, a globular body (as an approximate sphere), an ellipsoid, and other three-dimensional analogues with or without circular symmetry. Each support bar 212 includes a proximal portion 220 fixed to the shaft 202 and an opposing distal portion 222, and a central portion 224 therebetween. Each support bar 212 includes an electrically insulating member 230 having an insulating member proximal end 232 fixed to the distal end 204 of the shaft and an insulating member distal end 234 opposite to the insulating member proximal end 232.

[0067] Each support bar 212 further includes a conductive support member 240 partially disposed together with the insulating member 230, having a proximal end 242 disposed within the insulating member 230 and a distal portion 244 extending distally from the insulating member 230 and terminating at a distal end 246 or distal tip of the support member. Each conductive support member 240 is configured to be electrically coupled to an external electroporation control console 130 including a pulse generator, thereby being operable as a first ablation electrode configured to generate an electric field when a pulse waveform is delivered to each support member 240. The electrode assembly 210 further includes a plurality of support bar sensing electrodes 250 disposed along the insulating member 230.

[0068] The conduit 200 includes a support bar retainer 260 that is mechanically engaged with at least one of the proximal portions 220 or distal portions 222 of the support bars 212. In the illustrated example, the support bar retainer 260 includes a distal support bar retainer 262 that is mechanically coupled to the distal end 246 of the conductive support member of each support bar in the support bars 212, thereby mechanically connecting the distal portions 222 of the support bars together. Furthermore, the support bar retainer 260 includes a proximal support bar retainer 264 that mechanically abuts against the proximal portion 220 of each support bar in the support bars 212, thereby spaced the proximal portions 220 of the support bars apart in an expanded and contracted state.

[0069] In various embodiments, the elongated shaft 202 is formed of a biocompatible material that provides sufficient rigidity and flexibility to allow the shaft 202 to be guided through the patient's vascular system and to the treatment site, such as the chambers of the heart. In some embodiments, the shaft 202 is formed of a variety of different materials to allow the electroporation catheter 200 to have greater flexibility at the distal end 204 than at the proximal end. Furthermore, the shaft 202 may include tubular braided members to provide torsional stiffness and bending flexibility. The shaft 202 may include various markers for use with visualization systems, such as radiopaque or echo markers, or markers to facilitate visualization of the EAM electrodes.

[0070] The catheter shaft 202 may also accommodate a traction wire to deflect the electrode assembly 210 to the treatment site. The distal end 204 may include sensors (such as tracking sensors and force sensors) and additional elements (such as flushing elements). In the embodiment specifically illustrated, the electroporation catheter 200 includes a central strut 206 extending distally from the distal end 204 of the shaft 202. As shown, the central strut 206 extends partially into the interior space of the electrode assembly 210 and includes a strut electrode 207. An optional flushing lumen (not shown) is supported by the central strut 206. In embodiments, the central strut 206 may accommodate additional components. For example, in one embodiment, a magnetic guidance sensor (not shown) may be partially or entirely disposed within the central strut 206. However, in other embodiments, such a sensor may be located elsewhere on the electroporation catheter 200 (e.g., within the shaft 202). The strut electrode 207 can provide numerous functional advantages. In one example, the strut electrode 207 can serve as a reference for monopolar electrograms, replacing the reliance on surface ECG patch electrodes known in the art. For this purpose, the strut electrode 207 is positioned closer to the sensed tissue than conventional surface ECG methods, which advantageously minimizes far-field noise and provides a clearer unipolar electrogram than that obtainable using surface ECG electrodes. The strut electrode 207 is also operable for sensing and measuring other electrical parameters, such as the voltage between the strut electrode and the ablation electrode or other sensing electrode on the electrode assembly 210. This, in some examples, provides data that can be used to determine the shape of the electrode assembly during use, including when deformed by forces exerted on the heart wall, and displays the shape information via the EAM system 70.

[0071] In some embodiments, the distal end 204 of the shaft 202 includes exposed shaft electrodes 208, such as a plurality of exposed shaft electrodes, near the electrode assembly 210. The exposed shaft electrodes 208 in the embodiments can be used with the electrode assembly 210 and are configured as return electrodes in bipolar mode.

[0072] In some embodiments, electrode assembly 210 includes a coupling portion 216 and a deformable portion 218 of a basket. The coupling portion 216 of electrode assembly 210 is fixed to the distal end 204 of shaft 202, and the deformable portion 218 extends distally from the coupling portion 216. The deformable portion 218 of electrode assembly 210 can retract for delivery, for example, by introducing a sheath, and can expand for treatment at a treatment site. The coupling portion 216 is mechanically coupled directly or indirectly to catheter shaft 202. The coupling portion 216 may include components directly coupled to shaft 202 or coupled to a transition portion coupled to shaft 202. The coupling portion 216 of electrode assembly 210 is electrically coupled to a conduction path, such as a wire, extending along shaft 202 to the proximal end of shaft 202.

[0073] In the use of the electrophysiological system 50, the electroporation console 130 is electrically coupled to the coupling portion 216 of the electrode assembly 210 via a conduction path in the shaft 202. A deformable portion 218 of the electrode assembly 210 includes a proximal portion 220 mechanically and electrically coupled to the coupling portion 216. In an embodiment, the deformable portion 218 defines an open area through which blood or other fluids can flow. For example, support bars 212 form a concave shape around an internal cavity C, and a basket configuration provides openings between the support bars 212. The deformable portion 218 of the electrode assembly includes a cross-sectional dimension larger than the cross-sectional dimension of the shaft 202, such as a dimension substantially perpendicular to axis A. The electrode assembly 210 can provide wider lesions by electroporating tissue in a shorter time to create a pattern of overlapping lesions on the tissue, thereby reducing the likelihood of arrhythmia-inducing gaps, or the distal end can facilitate the delivery of more energy than a catheter-axis electrode to provide deeper lesions.

[0074] Insulator 230 is an electrical insulator that prevents the transfer of electrical energy to electrode assembly 210 via insulator 230. Insulator 230 is disposed at least on the proximal portion 220 of support bar 212 and surrounds conductive support member 240. For example, in this embodiment, insulator 230 extends completely around support member 240 located proximal to distal portion 244 and does not provide radial gaps exposing insulation of support member 240. Insulator 230 extends continuously from proximal end 222 to central portion 224 of support bar 212. For example, insulator 230 does not include longitudinal gaps exposing conductive support member 240 between proximal end 232 and distal end 234 of insulation member. In some embodiments, insulator 230 is composed of a polymer applied to conductive support member 240, such as by dip coating or spray coating of support bar 212. In some embodiments, insulator 230 is a tubular polymer, such as a shrink-fit polymer disposed around conductive support member 240 and attached in place. In addition to the proximal portion 220, the insulator may extend distally to the central portion 224, for example, to the distal side of the maximum radial dimension of the housing 212.

[0075] The conductive support member 240 provides a conductive structure that can be configured with the system 50 as a single ablation electrode. The conductive support member 240 receives electrical energy and is configured to generate an electric field to achieve irreversible electroporation in selected cardiac tissue. In embodiments, the conductive support member 240 is an axial element comprising a thin conductor to form a support strip 212 and define an open area. Examples of the conductive support member 240 include flexible round wires, pins, metal strips, bands, flat wires, and sheets. In some embodiments, the conductive support member 240 may be formed of a conductive shape memory material (such as a nickel-titanium alloy) that transitions to an expanded state once the contraction device applying the axial force is removed, or it may be formed of another conductive material that expands and contracts via a controllable mechanism.

[0076] In some embodiments, electrode assembly 210 includes one or more additional electrodes, such as sensing or mapping electrodes 250 in addition to conductive support member 240. For example, multiple sensing electrodes 250 may be attached to insulating member 230 at selected locations and electrically insulated from conductive support member 240. In the illustrated embodiment, the sensing electrodes 250 of each support bar 212 are spaced apart from each other. The sensing electrodes 250 are configured to sense cardiac electrical signals, such as locating electrode assembly 210 within a patient's anatomy via EAM system 70, and determining proximity to target tissue within the anatomy, etc. The sensing electrodes 250 in electrode assembly 210 may be electrically coupled to one or more lead conductors along the length of extension shaft 202, the lead conductors being configured to carry electrical signals received at the sensing electrodes 250. In embodiments, one or more sensing electrodes 250 may be configured to carry electrical signals provided to conductive support member 240 and operate together as ablation electrodes, such as in unipolar mode. In another embodiment, one or more sensing electrodes 250 may be configured to carry another electrical signal provided to at least one sensing electrode 250 and operate as a second ablation electrode.

[0077] In the illustrated example, the support bar retainer 260 includes a distal support bar retainer 262 and a proximal support bar retainer 264. Embodiments of the conduit 100 may include a distal support bar retainer, a proximal support bar retainer, or both. The distal support bar retainer 262 is mechanically coupled to the distal end 246 of the conductive support member of each support bar 212, thereby mechanically connecting the distal portions 222 of the support bars together. In embodiments, the distal support bar retainer 262 is conductive and electrically coupled to one or more support members 240, and is configured to form part of a first ablation electrode. In some embodiments, the distal support bar retainer 262 is configured to operate as a distal sensing electrode and is electrically insulated from the conductive member 240. The distal support bar retainer 262 is disposed at the distal end 246 of the electrode assembly and, in the illustrated embodiment, is a conductive ball. In one embodiment, the distal support bar retainer 262 is a multi-piece assembly having a first piece 264 near the distal end 246, which is mechanically coupled to a second piece 266 located distal to the distal end 246. The distal support bar retainer 262 may include a plurality of openings 268 arranged circumferentially around the assembly to receive conductive support members 240. The proximal support bar retainer 264 mechanically abuts against the proximal portion 220 of each support bar 212, thereby spaced the proximal portions 220 apart in expanded and contracted states. In the illustrated example, the proximal support bar retainer 264 may include a cap near the distal portion 204 of the shaft 202 having a plurality of openings to receive the support bar 212 into the shaft 202.

[0078] In various embodiments, catheter 200 is configured to operate in a bipolar mode to generate an electric field for electroporation. During bipolar operation of catheter 200, support bar 212 is configured as an anode (or cathode), and a second set of one or more electrodes (e.g., exposed axial electrode 208) at the distal portion 205 of catheter 200 is configured as a cathode (or anode) to generate the electric field. In this example, the aforementioned pad-shaped diffusion electrode is not used, and the electric field typically does not extend through the patient's body but rather through a localized portion of tissue near electrode assembly 210. In embodiments, catheter 200 is also configured to operate in a unipolar mode to generate an electric field for electroporation. For example, support bar 212 may be electrically coupled to a single lead conductor extending the length of axial 202, or coupled to a set of lead conductors in axial 202 configured to carry the same electrical signal to generate the electric field. Support bar 212 is configured as either an anode or a cathode. Neither the distal end 204 of the electrode or catheter shaft 202 in electrode assembly 210 is configured as the other of the cathode or anode. Instead, during electroporation, the other of the cathode or anode is positioned as a pad-shaped diffusion electrode located on the patient. An electric field is formed between the exposed conductive portion of the support strip and any other activated electrode or distal end 204 of electrode assembly 210, as well as the pad-shaped diffusion electrode.

[0079] Figure 3 A segment of conductive support member 300 is shown, which can be incorporated into conduit 100, such as as conductive support member 240 incorporated into electrode assembly 210. Conductive support member 300 may include features that help reduce strain on support strip 212 during expansion and contraction states and during transitions between expansion and contraction states. In some embodiments, conductive support member 300 may have a plurality of cross-sectional geometries 302 extending along length 304, such as thinner or flatter longitudinal segments 306 in other circular cross-sections 308, which helps reduce strain. In some embodiments, conductive support member 300 may have a varying (two-dimensional) profile extending along length 304, such as side cutouts 310 in other straight edges 312. Various combinations of zero or more cross-sectional geometries or profiles may be included in one or more conductive support members.

[0080] Figure 4An embodiment of an electroporation catheter 400 or its distal region 405 for ablating cardiac tissue is shown, which may be an example of catheter 100 and used in conjunction with an electrophysiological system 50. The electroporation catheter 400 may include the features and advantages of electroporation catheter 200. The electroporation catheter 400 includes a tubular shaft 402 defining a longitudinal axis A and having a distal end 404 of the shaft 402 and an opposing proximal end of the shaft. The longitudinal axis A is represented as a line passing through the centroid of the cross-section of the shaft 402. The distal region 405 of the catheter 400 is configured to be deployed close to target tissue, such as within a chamber of a patient's heart. An expandable electrode assembly 410 is coupled to the distal end 404 of the shaft and configured to generate an electric field. In one example, the electric field creates irreversible electroporation in selected cardiac tissue.

[0081] The electrode assembly 410 is convertible between a contracted state and an expanded state. In the expanded state, the electrode assembly 410 has a maximum radial dimension that is greater than the maximum radial dimension of the distal end 404 of the elongated shaft 402. The electrode assembly 410 includes a plurality of longitudinally extending support bars 412 that form a spherical basket 414 in the expanded state. Each support bar 412 includes a proximal portion 420 fixed to the shaft 402 and an opposing distal portion 422, as well as a central portion 424 between the proximal and distal portions.

[0082] Each support bar 412 includes an electrically insulating member 430 having an insulating member proximal end 432 fixed to a distal end 404 and an insulating member distal end 434 opposite to the insulating member proximal end 432. Each support bar 412 further includes a conductive support member 440 partially disposed together with the insulating member 430, the conductive support member having a support member proximal end 442 disposed within the insulating member 430 and a support member distal portion 444 extending distally from the insulating member 430 and terminating at the support member distal end 446. Each conductive support member 440 is configured to be electrically coupled to an external electroporation control console 130 including a pulse generator, thereby being operable as a first ablation electrode configured to generate an electric field when a pulse waveform is delivered to each support member 440. The electrode assembly 410 further includes a plurality of support bar sensing electrodes 450 disposed along the insulating member 430. Features of the insulating member 430 are described above with reference to the insulating member 230.

[0083] The conduit 400 includes a support bar retainer 460 that mechanically engages with at least one of the proximal portions 420 or distal portions 422 of the support bar 412. In the illustrated example, the support bar retainer 460 includes a distal support bar retainer 462 and a proximal support bar retainer 464. In this example, the proximal support bar retainer 464 is coupled to the distal end 404 of the shaft and mechanically abuts against the proximal portion 420 of each support bar 412, thereby spaced the proximal portions 420 of the support bars in both expanded and contracted states.

[0084] The distal end 404 of the catheter shaft may include sensors (such as tracking sensors and force sensors) and additional elements (such as flushing elements). In the embodiment specifically illustrated, the electroporation catheter 400 includes a central strut 406 extending distally from the distal end 404. As shown, the central strut 406 extends partially into the interior space of the electrode assembly 410 and includes strut electrodes 407. An optional flushing lumen (not shown) is supported by the central strut 406. In embodiments, the central strut 406 may accommodate additional components. For example, in one embodiment, a magnetic guidance sensor (not shown) may be partially or entirely disposed within the central strut 406. However, in other embodiments, such a sensor may be located elsewhere on the electroporation catheter 400 (e.g., within the shaft 402). As described above with reference to strut electrode 207, strut electrode 407 can serve as a reference for monopolar electrograms, replacing the reliance on surface ECG patch electrodes known in the art, and can also be used to sense and measure other electrical parameters, such as the voltage between the strut electrode and the ablation electrode or other sensing electrode on electrode assembly 410. Thus, in some examples, data that can be used to determine the shape of the electrode assembly during use, including when it is deformed by forces exerted on the heart wall, is provided and the shape information is displayed via EAM system 70.

[0085] In some embodiments, the distal end 404 of the shaft 402 includes an exposed shaft electrode 408, such as a plurality of exposed shaft electrodes, near the electrode assembly 410. The exposed shaft electrode 408 in the embodiments can be used with the electrode assembly 410 and is configured as a return electrode in a bipolar mode.

[0086] The electrode assembly 410 in this embodiment includes a coupling portion 416 and a deformable portion 418 of a basket. The coupling portion 416 of the electrode assembly 410 is fixed to the distal end 404 of the shaft 402, and the deformable portion 418 of the electrode assembly 410 extends distally from the coupling portion 416. The deformable portion 418 of the electrode assembly 410 can retract for delivery, for example, by introducing a sheath, and can expand for treatment at a treatment site. The coupling portion 416 of the electrode assembly 410 is mechanically coupled directly or indirectly to the catheter shaft 402. The coupling portion 416 is electrically coupled to a conduction path, such as a wire, extending along the shaft 402 to the proximal end of the shaft. In the use of the electrophysiological system 50, the electroporation console 130 is electrically coupled to the coupling portion 416 via the conduction path in the shaft 402. The deformable portion 418 of the electrode assembly 410 includes a proximal portion 420 mechanically and electrically coupled to the coupling portion 416. The deformable portion 418 of the electrode assembly 410 includes a cross-sectional dimension larger than the cross-sectional dimension of the shaft 402, such as a dimension that is approximately perpendicular to the axis A.

[0087] In the illustrated example, the support bar retainer 460 includes a distal support bar retainer 462 and a proximal support bar retainer 464. Embodiments of the conduit 100 may include a distal support bar retainer, a proximal support bar retainer, or both. The distal support bar retainer 462 is mechanically coupled to the distal end 246 of the conductive support member of each support bar 212, thereby mechanically connecting the distal portions 222 of the support bars together. In embodiments, the distal support bar retainer 262 is conductive and electrically coupled to one or more support members 240, and is configured to form part of a first ablation electrode. In some embodiments, the distal support bar retainer 262 is configured to operate as a distal sensing electrode and is electrically insulated from the conductive member 240. The distal support bar retainer 262 is disposed at the distal end 246 of the electrode assembly and, in the illustrated embodiment, is a conductive hub. In the illustrated example, the proximal support bar retainer 464 mechanically abuts against each support bar 412 to space the proximal portions 420 of the support bars in both expanded and contracted states. In the illustrated example, the proximal support bar retainer 464 is configured to abut against a proximal segment of the deformable portion 418 of the electrode assembly 410. For example, the central strut 406 is configured to include a plurality of longitudinally extending channels, grooves, or slots 466 to receive at least the inner surface of the support bars 412, for example, when the electrode assembly is in a contracted state, and to allow at least a portion of the support bars 412 to unfold from the grooves 466 when in an expanded state. The grooves 466 are configured to engage the deformable portions 418 of the electrode assembly 410 at least in the contracted configuration to space the proximal portions 420 of the support bars apart and to relieve strain. In the illustrated embodiment, the grooves 466 also at least partially engage the deformable portions 418 of the electrode assembly 410 in the expanded state.

[0088] It is readily understood that the order in which a method comprising one or more steps is listed is not a limitation of the claims unless expressly or implicitly stated otherwise in the specification or the claims themselves. It is well known that the methods shown are merely some examples among the many disclosed examples, and certain steps may be added or omitted without departing from the scope of this disclosure. These steps may include apparatus, systems, or methods or components thereof, as well as those known, conventional, and customary in the art.

[0089] The connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and / or physical connections between various elements. It should be noted that many alternative or additional functional relationships or physical connections may exist in actual systems. However, beneficial effects, advantages, problem solutions, and any elements that enable or make more significant such beneficial effects, advantages, or solutions should not be construed as critical, necessary, or indispensable features or elements. Therefore, the scope of the invention is not limited in any way except in the appended claims, where, unless expressly stated, the singular form of an element in the appended claims does not mean "one and only one," but rather "one or more." Furthermore, when phrases such as "at least one of A, B, or C" are used in the claims, such phrases are intended to be interpreted as meaning that A exists alone in an embodiment, B exists alone in an embodiment, C exists alone in an embodiment, or any combination of elements A, B, or C may exist in a single embodiment; for example, A and B, A and C, B and C, or A and B and C.

[0090] In the detailed description herein, references to "an embodiment," "embodiment," "example embodiment," etc., indicate that the described embodiment may include specific features, structures, or characteristics, but each embodiment does not necessarily include those specific features, structures, or characteristics. Furthermore, such phrases do not necessarily refer to the same embodiment. Additionally, when a specific feature, structure, or characteristic is described in connection with an embodiment, it is believed, based on the beneficial effects of this disclosure, that implementing such a feature, structure, or characteristic in conjunction with other embodiments is within the knowledge of those skilled in the art, whether explicitly described or not. After reading this specification, those skilled in the art will understand how to implement this disclosure with alternative embodiments.

[0091] Furthermore, no element, component, or method step in this disclosure is intended to be offered to the public, whether or not it is expressly recited in the claims. Unless an element is expressly stated using the phrase “means for…”, it shall not be interpreted in accordance with 35 USC 112(f). As used herein, the terms “comprising,” “including,” or any other variation thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but may also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0092] Various modifications and additions may be made to the exemplary embodiments discussed without departing from the scope of this disclosure. For example, while the above embodiments relate to specific features, the scope of this disclosure also includes embodiments with different combinations of features and embodiments that do not include all of the stated features. Therefore, the scope of this disclosure is intended to encompass all such substitutions, modifications, and variations falling within the scope of the claims, as well as all their equivalents.

Claims

1. A catheter for ablation of cardiac tissue via irreversible electroporation, the catheter comprising: A tubular shaft having a proximal portion and a distal end; An electrode assembly extending from the distal end of the shaft, the electrode assembly including a plurality of support bars, each support bar having a proximal support bar portion fixed to the shaft and an opposing distal support bar portion, each support bar including: A conductive support member having a proximal portion of the support member connected to a distal end of an axis and a distal portion of the support member terminating at the distal end of the support member, wherein each of the conductive support members is configured to operate as a first ablation electrode, the first ablation electrode being configured to generate an electric field when a pulse waveform is delivered to each support member; and An electrically insulating member covering the proximal portion of the support member, the insulating member having a proximal portion connected to the distal end of the shaft; and A plurality of sensing electrodes are disposed along the insulating member; and A support bar retainer that mechanically engages with at least one of the distal or proximal portions of the support member of each of the plurality of support bars, the support bar retainer being adapted to mechanically support the support bar.

2. The catheter according to claim 1, wherein, The support bar retainer includes a distal support bar retainer that is mechanically coupled to the distal end of the support member of each of the plurality of support bars, thereby mechanically connecting the distal portions of the support bars together.

3. The catheter according to claim 2, wherein, The distal support bar retainer is conductive and electrically connected to one or more support members, and is configured to form part of the first ablation electrode.

4. The catheter according to claim 2, wherein, The distal support bar retainer is configured to operate as a distal sensing electrode.

5. The catheter according to any one of claims 2-4, wherein, The distal support bar retainer is located at the distal end of the electrode assembly.

6. The catheter according to any one of claims 2-5, wherein, The distal support bar retainer is a conductive ball.

7. The catheter according to any one of claims 5-6, wherein, The distal support bar retainer includes a first piece located proximal to the distal end, the first piece being mechanically coupled to a second piece located distal to the distal end.

8. The catheter according to any one of claims 1-7, wherein, The first ablation electrode is configured as a unipolar ablation electrode.

9. The catheter according to any one of claims 1-8, further comprising an axial electrode disposed on the shaft near its distal end.

10. The catheter according to claim 9, wherein, The first ablation electrode and the axial electrode are configured to form an electrode pair for bipolar ablation.

11. The catheter according to any one of claims 1-10, wherein, At least one of the support bar sensing electrodes is configured to operate as a second ablation electrode.

12. The catheter according to claim 11, wherein, At least one of the support bar sensing electrodes and the first ablation electrode are configured to operate together as a unipolar ablation electrode.

13. The catheter according to any one of claims 1-12, wherein, The support bar retainer includes a proximal support bar retainer that mechanically abuts against the proximal portion of the support member of each of the plurality of support bars, thereby spacing the proximal portions of the support bars apart in an expanded and contracted state.

14. The catheter according to claim 13, wherein, The proximal support bar retainer is coupled to the distal end of the shaft and extends from the distal end of the shaft into the internal space formed by the electrode assembly.

15. The catheter according to claim 13, wherein, The proximal support bar retainer is integral with the distal end of the shaft.

16. A catheter for ablation of cardiac tissue via irreversible electroporation, the catheter comprising: A tubular shaft having a proximal portion and a distal end; An electrode assembly extending from the distal end of the shaft, the electrode assembly including a plurality of support bars, each support bar having a proximal support bar portion fixed to the shaft and an opposing distal support bar portion, each support bar including: A conductive support member having a proximal portion of the support member connected to a distal end of an axis and a distal portion of the support member terminating at the distal end of the support member, wherein each of the conductive support members is configured to operate as a first ablation electrode, the first ablation electrode being configured to generate an electric field when a pulse waveform is delivered to each support member; and An electrically insulating member covering the proximal portion of the support member, the insulating member having a proximal portion connected to the distal end of the shaft; and A plurality of sensing electrodes are disposed along the insulating member; and A support bar retainer that mechanically engages with at least one of the distal or proximal portions of the support member of each of the plurality of support bars, the support bar retainer being adapted to mechanically support the support bar.

17. The catheter according to claim 16, wherein, The support bar retainer includes a distal support bar retainer that is mechanically coupled to the distal end of the support member of each of the plurality of support bars, thereby mechanically connecting the distal portions of the support bars together.

18. The catheter according to claim 17, wherein, The distal support bar retainer is conductive and electrically connected to one or more of the support members, and is configured to form part of the first ablation electrode.

19. The catheter according to claim 17, wherein, The distal support bar retainer is configured to operate as a distal sensing electrode.

20. The catheter according to claim 19, wherein, The distal support bar retainer is located at the distal end of the electrode assembly.

21. The catheter according to claim 20, wherein, The distal support bar retainer is a conductive ball.

22. The catheter according to claim 20, wherein, The distal support bar retainer includes a first piece located proximal to the distal end, which is mechanically coupled to a second piece located distal to the distal end.

23. The catheter according to claim 16, wherein, The first ablation electrode is configured as a unipolar ablation electrode.

24. The catheter of claim 16, further comprising an axial electrode disposed on the axial shaft near its distal end.

25. The catheter according to claim 24, wherein, The first ablation electrode and the axial electrode are configured to form an electrode pair for bipolar ablation.

26. The catheter according to claim 16, wherein, At least one of the support bar sensing electrodes is configured to operate as a second ablation electrode.

27. The catheter according to claim 26, wherein, At least one of the support bar sensing electrodes and the first ablation electrode are configured to operate together as a unipolar ablation electrode.

28. The catheter according to claim 16, wherein, The support bar retainer includes a proximal support bar retainer that mechanically abuts against the proximal portion of the support member of each of the plurality of support bars, thereby spacing the proximal portions of the support bars apart in an expanded and contracted state.

29. The catheter according to claim 28, wherein, The proximal support bar retainer is coupled to the distal end of the shaft and extends from the distal end of the shaft into the internal space formed by the electrode assembly.

30. The catheter according to claim 28, wherein, The proximal support bar retainer is integral with the distal end of the shaft.

31. A catheter for ablation of cardiac tissue via irreversible electroporation, the catheter comprising: A tubular shaft having a proximal portion and a distal end; An electrode assembly extending from the distal end of the shaft, the electrode assembly including a plurality of support bars, each support bar having a proximal support bar portion fixed to the shaft and an opposing distal support bar portion; An electrically insulating member covering the proximal portion of the support bar, the insulating member having a proximal portion connected to the distal end of the shaft; Multiple sensing electrodes are disposed along the insulating member; and A support bar retainer that mechanically engages with at least one of the proximal and distal portions of the support bar, the support bar retainer being adapted to mechanically support the support bar.

32. The catheter according to claim 31, wherein, The support bar retainer includes a distal support bar retainer mechanically coupled to the distal end of the distal portion of each support bar, thereby mechanically coupling the distal portion of the support bar.

33. The catheter according to claim 32, wherein, The distal support bar retainer is conductive and is configured to form part of the first ablation electrode.

34. The catheter according to claim 33, wherein, The distal support bar retainer is a conductive ball.

35. The catheter according to claim 31, wherein, The support bar retainer is attached to the distal end of the shaft and extends from the distal end of the shaft into the internal space formed by the electrode assembly.

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