ELECTRODE SHORTING

In one embodiment, a medical system includes a catheter configured to be inserted into a body part of a living subject, and including a deflectable element having a distal end, an expandable distal end assembly disposed at the distal end of the deflectable element, and comprising a plurality of assembly electrodes, and configured to expand from a collapsed form to an expanded deployed form, a proximal electrode disposed at the distal end of the deflectable element proximally to the expandable distal end assembly, and extending circumferentially around the deflectable element, at least one electrical connection configured to electrically connect together at least two of the assembly electrodes to act as a combined assembly electrode, and an ablation power generator configured to be connected to the catheter, and apply an electrical signal between the combined assembly electrode and a selected electrode.

FIELD OF THE INVENTION

The present invention relates to medical devices, and in particular, but not exclusively to, ablation catheters.

BACKGROUND

A wide range of medical procedures involve placing probes, such as catheters, within a patient's body. Location sensing systems have been developed for tracking such probes. Magnetic location sensing is one of the methods known in the art. In magnetic location sensing, magnetic field generators are typically placed at known locations external to the patient. A magnetic field sensor within the distal end of the probe generates electrical signals in response to these magnetic fields, which are processed to determine the coordinate locations of the distal end of the probe. These methods and systems are described in U.S. Pat. Nos. 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612 and 6,332,089, in PCT International Publication No. WO 1996/005768, and in U.S. Patent Application Publications Nos. 2002/0065455 and 2003/0120150 and 2004/0068178. Locations may also be tracked using impedance or current based systems.

One medical procedure in which these types of probes or catheters have proved extremely useful is in the treatment of cardiac arrhythmias. Cardiac arrhythmias and atrial fibrillation in particular, persist as common and dangerous medical ailments, especially in the aging population.

Diagnosis and treatment of cardiac arrhythmias include mapping the electrical properties of heart tissue, especially the endocardium, and selectively ablating cardiac tissue by application of energy. Such ablation can cease or modify the propagation of unwanted electrical signals from one portion of the heart to another. The ablation process destroys the unwanted electrical pathways by formation of non-conducting lesions. Various energy delivery modalities have been disclosed for forming lesions, and include use of microwave, laser and more commonly, radiofrequency energies to create conduction blocks along the cardiac tissue wall. In a two-step procedure, mapping followed by ablation, electrical activity at points within the heart is typically sensed and measured by advancing a catheter containing one or more electrical sensors into the heart, and acquiring data at a multiplicity of points. These data are then utilized to select the endocardial target areas at which the ablation is to be performed.

Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity. In use, the electrode catheter is inserted into a major vein or artery, e.g., femoral vein, and then guided into the chamber of the heart of concern. A typical ablation procedure involves the insertion of a catheter having a one or more electrodes at its distal end into a heart chamber. A reference electrode may be provided, generally taped to the skin of the patient or by means of a second catheter that is positioned in or near the heart. RF (radio frequency) current is applied through the tip electrode(s) of the ablating catheter, and current flows through the media that surrounds it, i.e., blood and tissue, between the tip electrode(s) and an indifferent electrode. The distribution of current depends on the amount of electrode surface in contact with the tissue as compared to blood, which has a higher conductivity than the tissue. Heating of the tissue occurs due to its electrical resistance. The tissue is heated sufficiently to cause cellular destruction in the cardiac tissue resulting in formation of a lesion within the cardiac tissue which is electrically non-conductive.

Irreversible electroporation (IRE) applies short electrical pulses that generate high enough electrical fields (typically greater than 450 Volts per centimeter) to irreversibly damage the cells. Non-thermal IRE may be used in treating different types of tumors and other unwanted tissue without causing thermal damage to surrounding tissue. Small electrodes are placed in proximity to target tissue to apply short electrical pulses. The pulses increase the resting transmembrane potential, so that nanopores form in the plasma membrane. When the electricity applied to the tissue is above the electric field threshold of the target tissue, the cells become permanently permeable from the formation of nanopores. As a result, the cells are unable to repair the damage and die due to a loss of homeostasis and the cells typically die by apoptosis.

IRE may be used for cardiac ablation as an alternative to other cardiac ablation techniques, e.g., radio-frequency (RF) cardiac ablation. IRE cardiac ablation is sometimes referred to as Pulse Field Ablation (PFA). As IRE is generally a low thermal technique, IRE may reduce the risk of collateral cell damage that is present with the other techniques. e.g., in RF cardiac ablation.

US Patent Publication No. 2020/0069364 to Salahieh, et al., describes cardiac tissue ablation catheters including an inflatable and flexible toroidal or spherically shaped balloon disposed at a distal region of an elongate member, a flexible circuit carried by an outer surface of the balloon, the flexible circuit including, a plurality of flexible branches conforming to the radially outer surface of the balloon, each of the plurality of flexible branches including a substrate, a conductive trace carried by the substrate, and an ablation electrode carried by the substrate, the ablation electrode in electrical communication with the conductive trace, and an elongate shaft comprising a guidewire lumen extending in the elongate member and extending from a proximal region of the inflatable balloon to distal region of the inflatable balloon and being disposed within the inflatable balloon, wherein a distal region of the elongate shaft is secured directly or indirectly to the distal region of the inflatable balloon.

U.S. Pat. No. 8,295,902 to Salahieh, et al., describes a tissue electrode assembly including a membrane configured to form an expandable, conformable body that is deployable in a patient. The assembly further includes a flexible circuit positioned on a surface of the membrane and comprising at least one base substrate layer, at least one insulating layer and at least one planar conducting layer. An electrically-conductive electrode covers at least a portion of the flexible circuit and a portion of the surface of the membrane not covered by the flexible circuit, wherein the electrically-conductive electrode is foldable upon itself with the membrane to a delivery conformation having a diameter suitable for minimally-invasive delivery of the assembly to the patient.

U.S. Pat. No. 10,470,682 to Deno, et al., describes a system for determining electrophysiological data comprising an electronic control unit configured to acquire electrophysiology signals from a plurality of electrodes of one or more catheters, select at least one clique of electrodes from the plurality of electrodes to determine a plurality of local E field data points, determine the location and orientation of the plurality of electrodes, process the electrophysiology signals from the at least one clique from a full set of bipole sub-cliques to derive the local E field data points associated with the at least one clique of electrodes, derive at least one orientation independent signal from the at least one clique of electrodes from the information content corresponding to weighted parts of electrogram signals, and display or output catheter orientation independent electrophysiologic information to a user or process.

US Patent Publication No. 2014/0200578 to Groff, et al., describes medical devices for ablating nerves perivascularly and methods for making and using the same. An example medical device may include an expandable frame slidably disposed within a catheter shaft. The expandable frame may be configured to shift between a collapsed configuration and an expanded configuration. One or more electrodes may be disposed on a surface of the expandable frame. The one or more electrodes may be disposed radially inward relative to the greatest radial extent of the expandable frame when the expandable frame is in the expanded configuration.

U.S. Pat. No. 6,004,269 to Crowley, et al., describes an acoustic imaging system for use within a heart has a catheter, an ultrasound device incorporated into the catheter, and an electrode mounted on the catheter. The ultrasound device directs ultrasonic signals toward an internal structure in the heart to create an ultrasonic image, and the electrode is arranged for electrical contact with the internal structure. A chemical ablation device mounted on the catheter ablates at least a portion of the internal structure by delivery of fluid to the internal structure. The ablation device may include a material that vibrates in response to electrical excitation, the ablation being at least assisted by vibration of the material. The ablation device may alternatively be a transducer incorporated into the catheter, arranged to convert electrical signals into radiation and to direct the radiation toward the internal structure. The electrode may be a sonolucent structure incorporated into the catheter.

US Patent Publication No. 2018/0125576 to Rubinstein, et al., describes a medical apparatus, used to acquire electrical activity of patient anatomy, which includes an elongated body and a tip portion coupled to the elongated body. The tip portion includes one or more inflatable sections. Each inflatable section has a plurality of electrodes disposed on one of: (i) an outer surface of the one or more inflatable sections; and (ii) an inner surface and the outer surface of the one or more inflatable sections. The one or more inflatable sections, when inflated, cause a portion of the plurality of electrodes to contact a surface of an organ and provide a pathway for physiological fluid to flow through the tip portion. In one embodiment, the tip portion is a tulip balloon tip portion. In another embodiment, the tip portion is an inflatable tip portion having one or more concentrically wound inflatable sections.

EP Patent Publication 3576657A1 describes electroporation systems and methods of energizing a catheter for delivering electroporation. A catheter for delivering electroporation includes a distal section and an electrode assembly. The distal section is configured to be positioned in a vein within a body. The vein defines a central axis. The electrode assembly is coupled to the distal section and includes a structure and a plurality of electrodes distributed thereabout. The structure is configured to at least partially contact the vein. Each of the electrodes is configured to be selectively energized to form a circumferential ring of energized electrodes that is concentric with the central axis of the vein.

SUMMARY

There is provided in accordance with an embodiment of the present invention, a medical system including a catheter configured to be inserted into a body part of a living subject, and including a deflectable element having a distal end, an expandable distal end assembly disposed at the distal end of the deflectable element, and including a plurality of assembly electrodes, and configured to expand from a collapsed form to an expanded deployed form, a proximal electrode disposed at the distal end of the deflectable element proximally to the expandable distal end assembly, and extending circumferentially around the deflectable element, at least one electrical connection configured to electrically connect together at least two of the assembly electrodes to act as a combined assembly electrode, and an ablation power generator configured to be connected to the catheter, and apply an electrical signal between the combined assembly electrode and a selected electrode.

Further in accordance with an embodiment of the present invention the selected electrode is the proximal electrode.

Still further in accordance with an embodiment of the present invention the at least one electrical connection permanently electrically connects together the at least two assembly electrodes to act as the combined assembly electrode.

Additionally, in accordance with an embodiment of the present invention the at least one electrical connection is configured to electrical connect together all of the assembly electrodes to act as the combined assembly electrode.

Moreover, in accordance with an embodiment of the present invention the at least one electrical connection permanently electrically connects together all of the assembly electrodes to act as the combined assembly electrode.

Further in accordance with an embodiment of the present invention the expandable distal end assembly includes at least one of an expandable basket including a plurality of splines, the electrodes being disposed on the splines, or an inflatable balloon with the electrodes disposed thereon.

Still further in accordance with an embodiment of the present invention the proximal electrode includes irrigation holes through which to irrigate the body part, the catheter also including an irrigation tube disposed in the deflectable element and configured to be in fluid communication with the irrigation holes of the proximal electrode.

Additionally, in accordance with an embodiment of the present invention the irrigation holes are disposed radially around the proximal electrode.

Moreover, in accordance with an embodiment of the present invention the irrigation holes are disposed longitudinally along the proximal electrode.

Further in accordance with an embodiment of the present invention the proximal electrode and the deflectable element define an annular hollow therebetween, the irrigation tube being coupled to transfer irrigation fluid into the hollow, the irrigation tube being in fluid communication with the irrigation holes via the hollow.

Still further in accordance with an embodiment of the present invention, the system includes an irrigation reservoir configured to store irrigation fluid, and a pump configured to be connected to the irrigation reservoir and the catheter, and to pump the irrigation fluid from the irrigation reservoir through the irrigation holes via the irrigation tube.

Additionally, in accordance with an embodiment of the present invention the ablation power generator is configured to apply the electrical signal between the combined assembly electrode and the proximal electrode to perform electroporation of tissue of the body part.

Moreover, in accordance with an embodiment of the present invention, the system includes an irrigation tube disposed in the deflectable element and configured to deliver irrigation fluid into a region surrounded by the expandable distal end assembly.

Further in accordance with an embodiment of the present invention the proximal electrode has a maximum thickness measured perpendicular to the axis of the deflectable element of at least 0.05 mm and an inner diameter in the range of 2 mm to 6 mm.

Still further in accordance with an embodiment of the present invention the proximal electrode and the distal end of the deflectable element define an annular region therebetween, the catheter also including thermally conductive material disposed in the annular region, the thermally conductive material being formed from a different material than the proximal electrode.

There is also provided in accordance with another embodiment of the present invention, a medical system including a catheter configured to be inserted into a body part of a living subject, and including a deflectable element having a distal end, an expandable distal end assembly disposed at the distal end of the deflectable element, and including a plurality of assembly electrodes, and configured to expand from a collapsed form to an expanded deployed form, at least one electrical connection permanently electrically connecting together at least two of the assembly electrodes to act as a combined assembly electrode, and an ablation power generator configured to be connected to the catheter, and apply an electrical signal to the combined assembly electrode so as to ablate tissue of the body part.

Additionally, in accordance with an embodiment of the present invention the at least one electrical connection permanently electrically connects together all of the assembly electrodes to act as the combined assembly electrode.

Moreover, in accordance with an embodiment of the present invention the expandable distal end assembly includes at least one of an expandable basket including a plurality of splines, the electrodes being disposed on the splines, or an inflatable balloon with the electrodes disposed thereon.

Further in accordance with an embodiment of the present invention the ablation power generator is configured to apply the electrical signal to the combined assembly electrode so as to perform electroporation of tissue of the body part.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Overview

A balloon catheter or another catheter with an expandable distal end assembly such as a basket catheter may include electrodes on the distal end assembly that may be used for ablation, such as RF ablation or IRE ablation. In order to ablate a large area, a physician may need to reposition the catheter in order to adequately cover the area. This is time consuming.

Embodiments of the present invention solve the above problem by electrically connecting some or all of the electrodes of a distal end assembly of a catheter to act as a combined assembly electrode. An ablation power generator, connected to the catheter, applies an electrical signal to the combined assembly electrode to perform ablation (e.g., electroporation) of the tissue of the body part.

A return electrode may be used so that the ablation current is applied between the combined assembly electrode of the distal end assembly electrodes and a return electrode. In some cases, when the return electrode is one of the electrodes on the distal end assembly or in the middle of the distal end assembly, the ablation current may avoid travelling through the tissue thereby reducing the efficacy of the ablation current. Therefore, in some embodiments, the catheter includes a proximal electrode placed proximally to the distal end assembly. The ablation power generator applies an electrical signal between the combined assembly electrode and the proximal electrode to perform ablation (e.g., electroporation) of tissue of the body part.

Placing the return electrode proximally to the expandable distal end assembly helps prevent the ablation current from travelling inside the distal end assembly. However, due to the concentration of the ablation energy at the proximal return electrode, the proximal return electrode may overheat or cause charring of tissue.

Embodiments of the present invention solve the above problems by providing an irrigated proximal electrode, which is placed at the distal end of a deflectable element of the catheter, proximally to the distal end assembly. The proximal electrode extends circumferentially around the deflectable element, and includes irrigation holes through which to irrigate the body part to prevent overheating and charring. An irrigation tube placed in the deflectable element is in fluid communication with the irrigation holes of the proximal electrode. The irrigation holes are generally placed radially around, and longitudinally along, the proximal electrode.

In some embodiments, the proximal electrode and the deflectable element define an annular hollow therebetween with the irrigation tube coupled to transfer irrigation fluid into the hollow so that the irrigation tube is in fluid communication with the irrigation holes via the hollow. A pump pumps irrigation fluid from an irrigation reservoir via the irrigation tube into the hollow and out of the irrigation holes.

The ablation power generator is connected to the catheter, and applies an electrical signal between the combined assembly electrode and the proximal electrode to perform radio-frequency (RF) ablation or electroporation of the tissue of the body part.

In some embodiments, the expandable distal end assembly is also irrigated. A second irrigation tube may be placed in the deflectable element and delivers irrigation fluid into a region surrounded by the expandable distal end assembly. In some embodiments, the electrodes of the expandable distal end assembly (e.g., a balloon assembly) include irrigation holes that are in fluid communication with the second irrigation tube. In some embodiments, the irrigation of the expandable distal end assembly and the proximal electrode share the same irrigation tube.

In other embodiments, the proximal electrode is not irrigated. The distal end of the deflectable element and the proximal electrode define an annular region therebetween. Thermally conductive material is placed in the annular region to dissipate heat from the tissue around the proximal electrode thereby preventing or reducing overheating and charring. The thermally conductive material may be formed from a different material than the proximal electrode.

In other embodiments, the proximal electrode is formed from a thick piece of thermally conductive material to dissipate heat from the tissue around the proximal electrode thereby preventing or reducing overheating and charring. In some embodiments, the proximal electrode has a maximum thickness measured perpendicular to the axis of the deflectable element of at least 0.05 mm and an inner diameter in the range of about 2 mm to 6 mm.

System Description

Reference is now made toFIG. 1, which is a schematic view of a medical system20constructed and operative in accordance with an exemplary embodiment of the present invention. The system20includes a catheter40configured to be inserted into a body part of a living subject (e.g., a patient28). A physician30navigates the catheter40(for example, a basket catheter produced Biosense Webster, Inc. of Irvine, Calif., USA), to a target location in a heart26of the patient28, by manipulating an elongated deflectable element22of the catheter40, using a manipulator32near a proximal end of the catheter40, and/or deflection from a sheath23. In the pictured embodiment, physician30uses catheter40to perform electro-anatomical mapping of a cardiac chamber and ablation of cardiac tissue.

Catheter40includes an expandable distal end assembly35(e.g., a basket assembly), which is inserted in a folded configuration, through sheath23, and only after the catheter40exits sheath23does the distal end assembly35regain its intended functional shape. By containing distal end assembly35in a folded configuration, sheath23also serves to minimize vascular trauma on its way to the target location.

Catheter40includes a plurality of electrodes48disposed on the expandable distal end assembly35for sensing electrical activity and/or applying ablation power to ablate tissue of the body part (inset25). The catheter40also includes a proximal electrode21disposed on the deflectable element22proximal to the expandable distal end assembly35. Catheter40may incorporate a magnetic position sensor (not shown) at the distal edge of deflectable element22(i.e., at the proximal edge of the distal end assembly35). Typically, although not necessarily, the magnetic sensor is a Single-Axis Sensor (SAS). A second magnetic sensor (not shown) may be included at any suitable position on the assembly35. The second magnetic sensor may be a Triple-Axis Sensor (TAS) or a Dual-Axis Sensor (DAS), or a SAS by way of example only, based for example on sizing considerations. The magnetic sensors, the proximal electrode21, and electrodes48disposed on the assembly35are connected by wires running through deflectable element22to various driver circuitries in a console24.

In some embodiments, system20comprises a magnetic-sensing sub-system to estimate an ellipticity of the basket assembly35of catheter40, as well as its elongation/retraction state, inside a cardiac chamber of heart26by estimating the elongation of the basket assembly35from the distance between the magnetic sensors. Patient28is placed in a magnetic field generated by a pad containing one or more magnetic field generator coils42, which are driven by a unit43. The magnetic fields generated by coil(s)42transmit alternating magnetic fields into a region where the body-part is located. The transmitted alternating magnetic fields generate signals in the magnetic sensors, which are indicative of position and/or direction. The generated signals are transmitted to console24and become corresponding electrical inputs to processing circuitry41.

The method of position and/or direction sensing using external magnetic fields and magnetic sensors, is implemented in various medical applications, for example, in the CARTO® system, produced by Biosense-Webster, and is described in detail in U.S. Pat. Nos. 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612 and 6,332,089, in PCT Patent Publication WO 96/05768, and in U.S. Patent Application Publication Nos. 2002/0065455 A1, 2003/0120150 A1 and 2004/0068178 A1.

Processing circuitry41, typically part of a general-purpose computer, is further connected via a suitable front end and interface circuits44, to receive signals from body surface-electrodes49. Processing circuitry41is connected to body surface-electrodes49by wires running through a cable39to the chest of patient28.

In an embodiment, processing circuitry41renders to a display27, a representation31of at least a part of the catheter40and a mapped body-part, responsively to computed position coordinates of the catheter40.

The medical system20may also include an ablation power generator69(such as an RF signal generator) configured to be connected to the catheter40, and apply an electrical signal between one or more of the electrodes48and the proximal electrode21. The medical system20may also include an irrigation reservoir71configured to store irrigation fluid, and a pump73configured to be connected to the irrigation reservoir71and the catheter40, and to pump the irrigation fluid from the irrigation reservoir71via an irrigation tube through irrigation holes of the catheter40as described in more detail with reference toFIGS. 5A and 5B.

The example illustration shown inFIG. 1is chosen purely for the sake of conceptual clarity.FIG. 1shows only elements related to the disclosed techniques for the sake of simplicity and clarity. System20typically comprises additional modules and elements that are not directly related to the disclosed techniques, and thus are intentionally omitted fromFIG. 1and from the corresponding description. The elements of system20and the methods described herein may be further applied, for example, to control an ablation of tissue of heart26.

Reference is now made toFIGS. 2 and 3.FIG. 2is a schematic view of the catheter40in a deployed form constructed and operative in accordance with an embodiment of the present invention.FIG. 3is a schematic view of the distal end of the catheter40ofFIG. 2in a collapsed form.

The catheter40is configured to be inserted into a body part (e.g., the heart26(FIG. 1)) of a living subject. The deflectable element22of the catheter40has a distal end33. The deflectable element22may be produced from any suitable material, for example, polyurethane or polyether block amide. The assembly35is disposed distally to the deflectable element22and may be connected to the deflectable element22via a proximal coupling member50at the distal end33. The proximal coupling member50typically comprises a hollow tube and may be formed from any suitable material, for example, but not limited to polycarbonate with or without glass filler, polyether ether ketone (PEEK) with or without glass filler, polyimide, polyamide, or Polyetherimide (PEI) with or without glass filler. The coupling member50may formed as an integral part of the deflectable element22or as part of the distal end assembly35or as a separate element which connects with the deflectable element22and the distal end assembly35.

The assembly35, which may include a basket assembly, may include multiple splines such as flexible strips55(only one labeled for the sake of simplicity) with the electrodes48disposed on the splines. In the embodiments ofFIGS. 2 and 3each flexible strip55includes a single electrode48(only some labeled for the sake of simplicity). The assembly35may include any suitable number of electrodes48with multiple electrodes48per strip55.

In the embodiment ofFIGS. 2 and 3, each flexible strip55is formed of Nitinol which is selectively covered with insulating material (for example, thermoplastic polymer resin shrink wrap (PET)) in the distal and proximal regions57(only some labeled for the sake of simplicity) of the flexible strips55leaving a central region59(only some labeled for the sake of simplicity) of the flexible strips55as an electrically active region to perform mapping and/or perform ablation or electroporation, by way of example. The structure of the assembly35may vary. For example, flexible strips55(or other splines) may include flexible printed circuit boards (PCBs), or a shape-memory alloy such as Nitinol. The electrically active region of each flexible strip55may be larger or smaller than that shown inFIG. 2, and/or more centrally or proximally disposed on each flexible strip55.

Embodiments described herein refer mainly to a basket distal-end assembly35, purely by way of example. In alternative embodiments, the disclosed techniques can be used with any other suitable type of distal-end assembly.

The distal end assembly35includes a distal portion61, and a proximal portion63, and is configured to expand from a collapsed form (shown inFIG. 3) to an expanded deployed form (shown inFIG. 2). The relaxed state of the distal end assembly35is the expanded deployed form shown inFIG. 2. The distal end assembly35is configured to collapse into the collapsed form when the catheter40is retracted in a sheath23(FIG. 1) and is configured to expand to the expanded deployed form when the catheter40is removed from the sheath23. The relaxed shape of the distal end assembly35may be set by forming the flexible strips55from any suitable resilient material such as Nitinol or PEI. In some embodiments, the relaxed state of the expandable distal end assembly35may be the collapsed form, and the expandable distal end assembly35is expanded using a pull wire or element connected to the distal portion61and fed through a lumen in the deflectable element22.

The proximal electrode21is disposed at the distal end33of the deflectable element22proximally to the expandable distal end assembly35, and generally extends circumferentially around the deflectable element22. The proximal electrode21includes irrigation holes65(only some labeled for the sake of simplicity) through which to irrigate the body part. The irrigation holes65are generally disposed radially around, and/or longitudinally along, the proximal electrode21. The irrigation holes may have any suitable diameter, for example, in the range of 25 to 100 microns. The holes may be formed using any suitable technique, for example, laser drilling or electrical discharge machining (EDM). The proximal electrode21may include any suitable number of holes, for example, in the range of 4 to 100 holes. In one example, the proximal electrode21includes 5 proximally disposed holes and 5 distally disposed holes. An additional irrigation tube85is disposed in element22as explained in greater detail subsequently.

The ablation power generator69(FIG. 1) is configured to be connected to the catheter40, and apply an electrical signal between at least one of the electrodes48and the proximal electrode21. In some embodiments, the ablation power generator69is configured to apply the electrical signal between at least one of the electrodes48and the proximal electrode21to perform electroporation of tissue of the body part.

Reference is now made toFIGS. 4A and 4B.FIG. 4Ais a cross-sectional view of the distal end of the catheter40ofFIG. 2.FIG. 4Bis a more detailed cross-sectional view of the distal end of the catheter40inside block B ofFIG. 4A.

The distal ends of the flexible strips55(only two labeled for the sake of simplicity) are folded over and connected to a distal connector75, which in some embodiments is a tube (e.g., polymer tube) or slug (e.g., polymer slug). The distal connector75may be formed from any suitable material, for example, but not limited to polycarbonate with or without glass filler, PEEK with or without glass filler, or PEI with or without glass filler. In some embodiments, the flexible strips55may be connected to the distal connector75without being folded over so that when the distal end assembly35is collapsed the flexible strips55are approaching a flat formation along their length. The proximal ends of the flexible strips55are connected to the proximal coupling member50. The flexible strips55may be connected to the distal connector75and the proximal coupling member50using a suitable adhesive, such as an epoxy adhesive.

In some embodiments, the catheter40includes a nose cap77inserted into the distal connector75. The nose cap77may be used to help secure the flexible strips55to the distal connector75. The nose cap77may be formed from any suitable material, for example, but not limited to polycarbonate with or without glass filler, PEEK with or without glass filler, or PEI with or without glass filler. The nose cap77may optionally be sized to provide a pressure fit against the flexible strips55to prevent the flexible strips55from being pulled away from the inner surface of the distal connector75.

In some embodiments, the thickness of the distal portions of the flexible strips55may be reduced (compared to the rest of the flexible strips55) to create hinges79(one hinge79per flexible strip55) to allow the flexible strips55to bend sufficiently between the collapsed form and the deployed expanded form of the expandable distal end assembly35. Only two of the hinges79are labeled for the sake of simplicity. The hinges79of the flexible strips55may be reinforced using a flexible material such as a yarn (not shown). The hinges79(including the yarn and covering layers) may have any suitable thickness, for example, in the range of about 10 to 140 microns. The yarn may comprise any one or more of the following: an ultra-high-molecular-weight polyethylene yarn; or a yarn spun from a liquid-crystal polymer. The yarn may be any suitable linear density, for example, in a range between about25denier and250denier.

Reference is now made toFIGS. 5A and 5B.FIG. 5Ais a cross-sectional view of the catheter40ofFIG. 2along line A:A.FIG. 5Bis a cross-sectional view of the catheter ofFIG. 2along line B:B.

FIGS. 5A and 5Bshow the proximal electrode21which extends circumferentially around the deflectable element22. The edges of the proximal electrode21may be connected to the deflectable element22using a suitable adhesive and/or using a covering such as a thermoplastic polymer resin shrink wrap.FIGS. 5A and 5Bshow some of the irrigation holes65(only some labeled for the sake of simplicity) in the proximal electrode21. The proximal electrode21may have any suitable length measured parallel to the direction of elongation of the deflectable element22, for example, in the range of about 2 and 10 mm.

The catheter40includes an irrigation tube81disposed in the deflectable element22and configured to be in fluid communication with the irrigation holes65of the proximal electrode21. The pump73(FIG. 1) is configured to be connected to the irrigation reservoir71(FIG. 1) and the catheter40, and to pump the irrigation fluid from the irrigation reservoir71through the irrigation holes65via the irrigation tube81.

The inner surface of the proximal electrode21and the deflectable element22define an annular hollow83therebetween. The irrigation tube81is coupled to the annular hollow83to transfer the irrigation fluid into the hollow83. The irrigation tube81is generally disposed on the other side of the annular hollow83to the irrigation holes65. Therefore, the irrigation tube81is in fluid communication with the irrigation holes65via the hollow83. The pump73(FIG. 1) is configured to pump the irrigation fluid from the irrigation reservoir71via the irrigation tube81into the hollow83and out of the irrigation holes65. The collection of the irrigation fluid in the annular hollow83acts to cool the outer surface of the proximal electrode21and not just the portions close to the irrigation holes65.

The catheter40may include another irrigation tube85disposed in the deflectable element22and configured to deliver irrigation fluid into a region87(FIG. 2) surrounded by the flexible strips55of the expandable distal end assembly35. The irrigation tube85typically extends into the expandable distal end assembly35as shown inFIGS. 2 and 3.

In some embodiments, the catheter40includes a position sensor89(such as a magnetic position sensor) disposed in the deflectable element22.FIGS. 5A and 5Balso show wires91disposed therein connecting the electrodes48, the proximal electrode21, and the position sensor89with the proximal end of the catheter40.

Reference is now made toFIG. 6, which is a schematic view of a catheter100in a deployed form constructed and operative in accordance with an alternative embodiment of the present invention. The catheter100is substantially the same as the catheter40ofFIGS. 2 and 3except for the following differences. The catheter100includes a proximal electrode106, which is not irrigated. The proximal electrode106may either be cooled by filling with a thermally conductive material as described with reference to a proximal electrode106-1ofFIG. 7, or by forming the proximal electrode from a thermally conductive material of sufficient thickness to dissipate heat as described with reference to a proximal electrode106-2ofFIG. 8.

Reference is now made toFIG. 7, which is a cross-sectional view of the catheter100ofFIG. 6along line C:C. The proximal electrode106-1and the distal end of the deflectable element22define an annular region102therebetween. The catheter100includes thermally conductive material104, which is disposed in the annular region102, generally, but not necessarily, filling the annular region102, and generally in contact with at least part of the inner surface of the proximal electrode106-1. The thermally conductive material104may be formed from a different material than the proximal electrode106-1.

The term “thermally conductive material”, as used in the specification and claims, is defined as a material with a thermal conductivity greater than or equal to 1 Watt per meter Kelvin (W/mK) at 25 degrees Centigrade. The thermally conductive material104may be any suitable thermally conductive material, for example, but not limited to, platinum, palladium, gold, or thermally conductive epoxy. In some embodiments, the thermally conductive material104is first wrapped around the outer surface of the deflectable element22, and then the proximal electrode106-1is wrapped around the thermally conductive material104. In other embodiments, the proximal electrode106-1is first fixed around the deflectable element22(as a single piece or from two halves subsequently joined together) and then the thermally conductive material104is injected below the proximal electrode106-1through a hole (not shown) in the proximal electrode106-1.

The wall thickness of the proximal electrode106-1may have any suitable value, for example, in the range of about 0.01 mm to 0.25 mm. The thickness of the thermally conductive material104may have any suitable value, for example, in the range of about 0.01 mm to 0.25 mm. The proximal electrode106-1may have any suitable length measured parallel to the direction of elongation of the deflectable element22, for example, between about 2 mm and 10 mm.

It should be noted that the irrigation tube81(FIGS. 5A and 5B) is not included within the deflectable element22shown inFIG. 7.

Reference is now made toFIG. 8, which is a cross-sectional view of the catheter100ofFIG. 6along line C:C constructed and operative in accordance with another alternative embodiment of the present invention. The proximal electrode106-2shown inFIG. 8has a wall thickness which is greater than the wall thickness of the proximal electrode106-1described with reference toFIG. 7.

The proximal electrode106-2may have any suitable wall thickness. In some embodiments, the proximal electrode106-2may have a maximum thickness measured perpendicular to the axis of the deflectable element22of at least 0.05 mm and an inner diameter in the range of 2 mm to 6 mm.

The proximal electrode106-2may have any suitable length measured parallel to the direction of elongation of the deflectable element22of between about 2 mm and 10 mm.

The proximal electrode106-2is formed from a thermally conductive material, which provides dissipation of heat formed during electroporation and/or RF ablation. The thermally conductive material may be any suitable thermally conductive material, for example, but not limited to, platinum, palladium, or gold.

The proximal electrode106-2may each be formed as a flat electrode which is wound around the outer surface of the deflectable element22to form a ring or as two half rings which are connected together around the deflectable element22.

Each proximal electrode106-2,106-1(FIG. 7),21(FIGS. 5A and 5B), has a non-uniform surface, which bulges away from the outer surface of the deflectable element22. The proximal electrodes may have any suitable shape. For example, the proximal electrode21,106-1,106-2may be formed as ring having a uniform outer diameter along the length of the proximal electrode21.

Reference is now made toFIG. 9, which is a schematic view of a balloon catheter200in a deployed form constructed and operative in accordance with yet another alternative embodiment of the present invention. The catheter200is substantially the same as the catheter40ofFIG. 2except that the catheter200includes an expandable distal end assembly202, which includes an inflatable balloon204with the electrodes206(only some labeled for the sake of simplicity) disposed thereon. The catheter200includes an irrigation tube208which is disposed in the deflectable element22and extends into a region210surrounded by the inflatable balloon204. The electrodes206of the expandable distal end assembly202include irrigation holes212(only some labeled for the sake of simplicity) that are in fluid communication with the irrigation tube208. The catheter200includes a proximal electrode214in substantially the same form as the proximal electrode21described with reference toFIGS. 5A and 5B. In some embodiments, the proximal electrode214may be replaced with the proximal electrode106-1ofFIG. 7or with the proximal electrode106-2ofFIG. 8.

Reference is now made toFIG. 10, which is a schematic view of electrode connections in the catheter40of medical system20constructed and operative in accordance with an exemplary embodiment of the present invention.

The catheter40may include one or more electrical connections230configured to electrically connect together at least two (and optionally all) of the assembly electrodes48to act as a combined assembly electrode232.

In some embodiments, the electrical connection(s)230may be configured to selectively connect together the assembly electrodes48to act as the combined assembly electrode232and also allow the electrodes48to act as individual electrodes, for example, for sensing positions, electrical activations, and performing individual ablation. In such embodiments, the electrical connections230may include switching circuitry (not shown) which enables selectively connecting together two or more (and optionally all) of the assembly electrodes48.

In other embodiments, the electrical connection(s)230permanently electrically connects together the at least two (and optionally all) of the assembly electrodes48to act as the combined assembly electrode232.

The ablation power generator69is configured to be connected to the catheter40, and apply an electrical signal (arrow234) to the combined assembly electrode232so as to ablate tissue of the body part. In some embodiments, the ablation power generator69is configured to apply the electrical signal234to the combined assembly electrode48so as to perform electroporation of tissue of the body part.

The electrical signal234is generally applied between the combined assembly electrode232and a return electrode. The return electrode may be located in any suitable location, for example, on the catheter40, as an indifferent electrode attached to the patient's skin or on another catheter. In some embodiments, the proximal electrode21acts as the return electrode.

Therefore, in some embodiments, the ablation power generator69is configured to apply an electrical signal between the combined assembly electrode232and the proximal electrode21. In some embodiments, the ablation power generator69is configured to apply the electrical signal between the combined assembly electrode232and the proximal electrode21to perform electroporation of tissue of the body part.

As previously mentioned, the ablation may lead to excessive heating in the region of the proximal electrode21. Therefore, the proximal electrode21may apply cooling to surrounding tissue using irrigation as described above with reference toFIGS. 2, 5A and 5B.

The electrical connections230may be implemented with other catheters to connect assembly electrodes together to form a combined assembly electrode.

In some embodiments, two or more (and optionally all) of the assembly electrodes48(FIG. 6) of the catheter100may be connected (selectively or permanently) using the electrical connections230. The proximal electrode106(FIG. 6) or any other suitable electrode may act as the return electrode. The proximal electrode106may provide cooling using the thermally conductive material104disposed in the annular region102(FIG. 7) of the proximal electrode106, as described in more detail above with reference toFIG. 7. Alternatively, the proximal electrode106may provide cooling by forming the proximal electrode106(FIG. 8) from a thermally conductive material having a maximum thickness measured perpendicular to the axis of the deflectable element of at least 0.05 mm and an inner diameter in the range of 2 mm to 6 mm, as described in more detail above with reference toFIG. 8.

In some embodiments, two or more (and optionally all) of the electrodes206of the expandable distal end assembly202of the catheter200ofFIG. 9may be connected (selectively or permanently) using the electrical connections230. The proximal electrode214(FIG. 9) or any other suitable electrode may act as the return electrode.