CN118000896A - Catheter, system and method for combining ablation modalities - Google Patents

Abstract

The title of the present disclosure is "catheters, systems, and methods for combining ablation modalities". The disclosed technology includes a method of ablating tissue, the method including positioning an electrode in contact with the tissue, and applying a first ablation signal to the tissue. The method may include forming a first ablation site including a first depth, wherein the temperature of the tissue has little or no first temperature change. The method may include applying a second ablation signal to the tissue that is different from the first ablation signal. Applying the second ablation signal to the tissue may include forming a second ablation focus including a second depth, and generating a second temperature change in the tissue, the second temperature change differing from the first temperature change by at least 10 ℃. The method may include forming a combined ablation site including the first ablation site and the second ablation site and including a combined size. The combined depth may be about 20% to about 40% greater than either of the first depth and the second dimension.

Description

Catheters, systems and methods for combined ablation modalities

Technical Field

The present invention relates to catheters particularly suitable for performing pulsed field ablation in or near the heart. The catheters may also be used for mapping and/or thermal ablation using radio frequency electrical signals.

Background technique

Arrhythmias such as atrial fibrillation occur when an area of cardiac tissue abnormally conducts electrical signals to adjacent tissue, disrupting the normal cardiac cycle and causing an irregular heartbeat. The source of the unwanted signals is typically located in the tissue of the atria and ventricles. Regardless of the source, the unwanted signals are conducted through cardiac tissue to other locations where they can initiate or perpetuate the arrhythmia.

Treatment of arrhythmias may include disrupting the conduction pathway of electrical signals to cause the arrhythmia to stop, or modifying the propagation of unwanted electrical signals from one part of the heart to another. Such procedures typically include a two-step process: (1) mapping; and (2) ablation. During mapping, a catheter having an end effector, preferably with a high density of electrodes, is moved across the target tissue, an electrical signal is acquired from each electrode, and a map is generated based on the acquired signals. During ablation, non-conductive lesions are formed at areas selected based on the map to disrupt the electrical signals passing through those areas. The most common ablation technique currently involves applying radiofrequency ablation (RFA) electrical signals to tissue via electrodes to generate heat. Irreversible electroporation (IRE) ablation is a recently developed technique that involves applying short duration high voltage pulses across tissue to cause cell death, sometimes referred to as pulsed field ablation (PFA). Typically, RFA and PFA are applied as separate and distinct techniques. In the context of the present disclosure, RFA may be interchangeably referred to as RF, and PFA may be referred to as PF.

The different goals of mapping, ablation using RF signals, and IRE ablation generally lead to different catheter design objectives. As a non-exhaustive list, some catheters with circular, semicircular, or spiral end effectors for mapping and/or ablation are described in the following patents and patent applications: U.S. Patent No. 6,973,339, U.S. Patent No. 7,371,232, U.S. Patent No. 8,275,440, U.S. Patent No. 8,475,450, U.S. Patent No. 8,600,472, U.S. Patent No. 8,608,735, U.S. Patent No. 9,050,010, U.S. Patent No. 9,788,893, U.S. Patent No. 9,848,948, U.S. Patent Publication No. 2017/0100188, U.S. Patent Publication No. 2021/0369338, U.S. Patent Application No. 17/570,829, U.S. Provisional Patent Application No. 63/336,094, and U.S. Provisional Patent Application No. 63/220,312, each of which is incorporated herein by reference, copies of which are provided in the Appendix.

Summary of the invention

In general, examples presented herein may include a method of ablating tissue. The method may include positioning an electrode in contact with the tissue, and applying a first ablation signal to the tissue using the electrode. Applying the first ablation signal to the tissue may include forming a first ablation lesion including a first depth, wherein the temperature of the tissue has little or no first temperature change.

The method may include applying a second ablation signal different from the first ablation signal to the tissue using the electrode. Applying the second ablation signal to the tissue may include forming a second lesion including a second depth and generating a second temperature change in the tissue that differs from the first temperature change by at least 10°C.

The method may include forming a combined lesion including a first lesion and a second lesion and including a combined size. The combined depth may be approximately 20% to approximately 40% greater than either of the first depth and the second size.

The first ablation signal and the second ablation signal may be applied to the tissue at least sequentially or simultaneously.

The positioning step may include applying a contact force of about 5 grams to about 40 grams between the tissue and the electrode.

The first ablation signal may be one of a radio frequency (RF) signal or a pulsed field (PF) signal, and the second ablation signal is the other of the RF signal or the PF signal.

The method may also include setting the power of the RF signal to about 1 watt to about 400 watts; maintaining the RF signal for about 1 second to about 60 seconds; and generating one of the first temperature change or the second temperature change of about 20°C to about 70°C.

The method may also include setting the voltage of the PF signal to about 900 volts to about 3000 volts.

The RF signal may form one of the first depth or the second depth between about 3 mm and about 5 mm.

The PF signal may form one of the first depth or the second depth between about 4 mm and about 6 mm.

The disclosed technology may include a system for electrophysiology use. The system may include: an alternating current (AC) signal generator configured to provide a radio frequency signal at high power; a direct current (DC) signal generator configured to provide high voltage pulses; and a catheter having an end effector.

The end effector may be electrically coupled to the AC signal generator and the DC signal generator. The end effector may include at least one electrode disposed on the end effector such that the at least one electrode delivers high voltage pulses from the at least one electrode to organ tissue within the patient's body, to a first return electrode and a second return electrode coupled to the outside of the patient's body, and delivers a radio frequency signal between the at least one electrode and one of the first return electrode or the second return electrode.

The radio frequency signal and the high voltage pulses may be applied to the organ tissue sequentially or simultaneously.

The end effector may include a cylindrical member having a distal tip electrode and irrigation ports disposed on the cylindrical member to provide irrigation fluid proximate the distal tip electrode.

The distal tip electrode may be coupled to a force sensor. The radio frequency signal may be applied with a contact force of about 5 grams or more. The radio frequency signal may be provided with a power of at least 25 watts at a frequency of about 350 kHz to about 500 kHz. The radio frequency signal may include a frequency of 350 kHz to about 500 kHz, and the radio frequency signal may be provided for a duration of at least 1 second.

The high voltage pulses may include an amplitude of at least 800V. The duration of each of the high voltage pulses may be less than 20 microseconds. A plurality of high voltage pulses may provide a pulse train of about 100 microseconds. A time gap selected from any value of 0.3 milliseconds to 1000 milliseconds may be provided between adjacent pulse trains. A plurality of pulse trains may provide a PFA burst. A PFA burst may include any value between 2 pulse trains to 100 pulse trains, wherein the duration of the PFA burst includes any value selected from 0 milliseconds to 500 milliseconds. The high voltage pulses may provide about 60 joules or less.

BRIEF DESCRIPTION OF THE DRAWINGS

The above aspects and additional aspects of the present invention will be further discussed with reference to the following description and in conjunction with the accompanying drawings, in which like numbers indicate similar structural elements and features in the various figures. The accompanying drawings are not necessarily drawn to scale, but instead, emphasis is placed on illustrating the principles of the present invention. The accompanying drawings depict one or more specific implementations of the present apparatus, system, and method by way of example only and not by way of limitation.

FIG1 is a schematic illustration of a medical system including an exemplary medical probe that may be used in accordance with the disclosed technology;

2A is a side view of a catheter for use with the system of FIG. 1 according to the disclosed technology;

2B is a perspective view of a catheter for use with the system of FIG. 1 according to the disclosed technology;

3 is a schematic cross-sectional view of a heart chamber with a catheter inside the chamber in contact with the heart wall in accordance with the disclosed technology;

4A and 4B are pictures depicting the depth of tissue treated using RF energy and PFA energy according to the disclosed technology;

FIG5 shows a flow chart of a method for ablating tissue using RF energy and PFA energy according to the disclosed technology;

FIG6A illustrates a basket catheter according to the disclosed technology;

FIG6B illustrates a circular catheter according to the disclosed technology;

FIG. 6C illustrates a planar array catheter in accordance with the disclosed technology.

Detailed ways

Documents incorporated herein by reference shall be considered to be an integral part of this application, except that, to the extent that any term is defined in these incorporated documents in a manner that contradicts a definition explicitly or implicitly made in this specification, only the definition in this specification shall prevail.

Although the example embodiments of the disclosed technology are explained in detail herein, it should be understood that other embodiments can be envisioned. Therefore, it is not intended that the scope of the disclosed technology be limited to the details of the construction and arrangement of the components set forth in the following description or shown in the accompanying drawings. The disclosed technology can have other embodiments and can be practiced or implemented in various ways. As understood by those skilled in the relevant art according to the teachings of this article, the features of the embodiments disclosed herein (including those disclosed in the attached appendix) can be combined.

As used herein, the term "about" or "approximately" for any numerical value or range indicates a suitable dimensional tolerance that allows a collection of parts or elements to achieve its intended purpose as described herein. More specifically, "about" or "approximately" may refer to a range of ±20% of the value of the recited value, for example, "about 90%" may refer to a range of values from 71% to 99%.

As discussed herein, the term "ablation" as it relates to the devices and corresponding systems of the present disclosure refers to components and structural features configured to reduce or prevent the generation of unstable cardiac signals. Non-thermal ablation includes the use of irreversible electroporation (IRE) to cause cell death, and is interchangeably referred to as pulsed electric fields (PEF) and pulsed field ablation (PFA) throughout this disclosure. Thermal ablation includes the use of extreme temperatures to cause cell death and includes RF ablation. "Ablation" as used throughout this disclosure, when referring to the devices and corresponding systems of the present disclosure, refers to the ablation of cardiac tissue used for certain conditions, including but not limited to arrhythmias, atrial flutter ablation, pulmonary vein isolation, supraventricular tachycardia ablation, and ventricular tachycardia ablation. As understood by those skilled in the relevant art, the term "ablation" includes various forms of body tissue ablation when referring to known methods, devices and systems as a whole.

As discussed herein, the terms "bipolar" and "monopolar" when used to refer to ablation regimens describe ablation regimens that differ in terms of current paths and electric field distribution. "Bipolar" refers to an ablation regimen that utilizes a current path between two electrodes as described below, both electrodes being positioned at a treatment site inside the body; the current density and electric flux density at each of the two electrodes are typically approximately equal. "Monopolar" refers to an ablation regimen that utilizes a current path between two electrodes as described below, wherein one electrode having a high current density and a high electric flux density is positioned at the treatment site, and a second electrode having a relatively lower current density and a lower electric flux density is positioned away from the treatment site, typically positioned outside the body via a contact patch.

As discussed herein, the terms "biphasic pulse" and "monophasic pulse" refer to corresponding electrical signals. "Biphasic pulse" refers to an electrical signal having a positive voltage phase pulse (referred to herein as "positive phase") and a negative voltage phase pulse (referred to herein as "negative phase"). "Monophasic pulse" refers to an electrical signal having only a positive phase or only a negative phase. Preferably, the system providing the biphasic pulse is configured to prevent the application of a direct current voltage (DC) to the patient. For example, the average voltage of the biphasic pulse may be zero volts relative to ground or other common reference voltage. Additionally or alternatively, the system may include a capacitor or other protective component. The voltage amplitude of the biphasic and/or monophasic pulses is described herein, and it should be understood that the voltage amplitude expressed is the absolute value of the approximate peak amplitude of each of the positive voltage phase and/or the negative voltage phase. Each phase of the biphasic pulse and the monophasic pulse preferably has a square shape, which has a substantially constant voltage amplitude during most of the phase duration. The phases of the biphasic pulse are separated in time by an interphase delay. The interphase delay duration is preferably less than or approximately equal to the duration of the phase of the biphasic pulse. The interphase delay duration is more preferably about 25% of the duration of a phase of the biphasic pulse.

As discussed herein, the terms "tubular" and "tube" should be interpreted broadly and are not limited to structures that are perfect cylinders or have a completely circular cross-section or a uniform cross-section throughout their length. For example, tubular structures are often shown as structures that are substantially perfect cylinders. However, tubular structures may have tapered or curved outer surfaces without departing from the scope of the present disclosure.

Referring to FIG. 1 , an exemplary catheter-based electrophysiological mapping and ablation system 10 is shown. The system 10 includes a plurality of catheters that are inserted into a chamber or vascular structure of a heart 12 by a physician 24 through the patient's vascular system via the skin. Typically, a delivery sheath catheter is inserted into the left atrium or right atrium near a desired location in the heart 12. Multiple catheters may then be inserted into the delivery sheath catheter to reach the desired location. The multiple catheters may include a catheter dedicated to sensing intracardiac electrogram (IEGM) signals, a catheter dedicated to ablation, and/or a catheter dedicated to both sensing and ablation. An exemplary catheter 14 configured for sensing IEGM is shown herein. The physician 24 brings the distal end 28 of the catheter 14 into contact with the heart wall for sensing a target site in the heart 12. For ablation, the physician 24 would similarly bring the distal end of the ablation catheter to the target site for ablation.

The catheter 14 is an exemplary catheter that includes one (preferably multiple) electrodes 26, optionally distributed on a plurality of spines 22 at a distal tip 28 and configured to sense IEGM signals. The catheter 14 may additionally include a position sensor 29 embedded in or near the distal tip 28 for tracking the position and orientation of the distal tip 28. Optionally and preferably, the position sensor 29 is a magnetically based position sensor that includes three magnetic coils for sensing three-dimensional (3D) position and orientation.

The magnetic-based position sensor 29 can operate with the positioning pad 25, which includes a plurality of magnetic coils 32 configured to generate a magnetic field in a predetermined working space. The real-time position of the distal tip 28 of the catheter 14 can be tracked based on the magnetic field generated by the positioning pad 25 and sensed by the magnetic-based position sensor 29. The details of the magnetic-based position sensing technology are described in U.S. Patent Nos. 5,5391,199, 5,443,489, 5,558,091, 6,172,499, 6,239,724, 6,332,089, 6,484,118, 6,618,612, 6,690,963, 6,788,967 and 6,892,091.

The system 10 includes one or more electrode patches 38 positioned in contact with the skin of the patient 23 to establish a position reference for impedance-based tracking of the positioning pad 25 and the electrodes 26. For impedance-based tracking, current is directed toward the electrodes 26 and sensed at the electrode skin patches 38 so that the position of each electrode can be triangulated via the electrode patches 38. Details of impedance-based position tracking techniques are described in U.S. Patents Nos. 7,536,218, 7,756,576, 7,848,787, 7,869,865, and 8,456,182. The electrode patches 38 (one or more) can be used as return electrodes (also called indifferent electrodes) during the monopolar mode of ablation, whereby electrical energy is provided by one or more electrodes on the catheter so that the electrical energy completes a circuit via the tissue to the indifferent (or return) electrode 38. In practice, in cases where the surface area of the electrode patches 38 is not large enough to handle the power transfer, two separate return electrode patches (whose surface area is larger than the surface area of the patches 38) are used separately from the electrode patches 38.

Recorder 11 displays electrograms 21 captured using body surface ECG electrodes 18 and intracardiac electrograms (IEGMs) captured using electrodes 26 of catheter 14. Recorder 11 may include pacing capabilities for pacing the cardiac rhythm and/or may be electrically connected to a separate pacemaker.

The system 10 may include an ablation energy generator 50 adapted to conduct ablation energy to one or more electrodes at the distal end of a catheter configured for ablation. The energy generated by the ablation energy generator 50 may include, but is not limited to, radio frequency (RF) energy or pulsed field ablation (PFA) energy (including monopolar or bipolar high voltage DC pulses that can be used to achieve irreversible electroporation (IRE)), or a combination thereof.

The patient interface unit (PIU) 30 is an interface configured to establish electrical communication between catheters, electrophysiology equipment, a power source, and a workstation 55 for controlling the operation of the system 10. The electrophysiology equipment of the system 10 may include, for example, multiple catheters, a positioning pad 25, surface ECG electrodes 18, electrode patches 38, an ablation energy generator 50, and a recorder 11. Optionally and preferably, the PIU 30 additionally includes processing capabilities for enabling real-time calculation of the position of the catheter and for performing ECG calculations.

Workstation 55 includes memory, a processor unit with memory or storage loaded with appropriate operating software, and user interface capabilities. Workstation 55 can provide multiple functions, optionally including: (1) three-dimensional (3D) modeling of endocardial anatomy and rendering of the model or anatomical map 20 for display on display device 27; (2) displaying activation sequences (or other data) compiled from recorded electrograms 21 on display device 27 as representative visual markers or images superimposed on the rendered anatomical map 20; (3) displaying real-time positions and orientations of multiple catheters within the heart chambers; and (5) displaying sites of interest (such as sites to which ablation energy has been applied) on display device 27. A commercial product embodying elements of system 10 can be purchased from Biosense Webster, Inc., 31A Technology Drive, Irvine, CA 92618 as the CARTO ^™ 3 system.

As shown in FIG. 2A , the catheter 14 may include an elongated catheter body 17, a deflectable intermediate section 19, a distal section 13 carrying at least a terminal electrode 15 on its distal tip 28, and a control handle 16. The catheter 14 may be a steerable multi-electrode lumen catheter with a deflectable tip designed to facilitate electrophysiological mapping of the heart 12 and transmit radiofrequency (RF) and pulsed field (PF) currents to the terminal electrode 15 for ablation purposes. A physician 24 (such as a cardiologist) may insert the catheter 14 through the vascular system of a patient 23 so that the distal section 13 of the catheter enters a chamber of the patient's heart 12. The physician 24 pushes the catheter so that the distal tip 28 of the catheter engages endocardial tissue at a desired location or locations. The catheter 14 is connected to a console 55 by a suitable connector at its proximal end. The console 55 may include an ablation energy generator 50 that supplies high frequency electrical energy (AC or DC) via the catheter 14 for ablating tissue in the heart 12 at the location where the distal section 13 engages. For ablation, the catheter 14 may be used in conjunction with a dispersive pad (e.g., a return electrode or an indifferent electrode). In this regard, the catheter 14 may include a shaft that measures 7.5F using an 8F ring electrode. The catheter 14 may also have a force sensing system near the distal tip electrode 15 that provides real-time measurement of the contact force between the catheter tip 15 and the wall of the heart 12 (and the contact angle between the tip electrode 15 and the tissue).

As shown in FIG2B , the distal end section 13 may include an electrode assembly 15 and at least one microelement having an atraumatic distal end adapted to be in direct contact with the target tissue. The catheter body 17 may have a longitudinal axis, and an intermediate section 19 located distal to the catheter body 17 that may be unidirectionally or bidirectionally deflected off-axis from the catheter body 12. Distal to the intermediate section 19 is an electrode assembly carrying at least one electrode 15. Proximal to the catheter body is a control handle 16 that allows an operator to manipulate the catheter, including deflection of the intermediate section 14.

The elongated catheter body can be a relatively highly torsionable shaft, wherein the distal end segment 13 is attached to the deflectable middle segment 19 and includes an electrode assembly 15 with an electrode array. For example, the distal end segment 13 may include a 3.5 mm end dome with three microelectrodes. All electrodes can be used for recording and stimulation purposes. The rocker 34 can be used to deflect the distal end portion 13. The high torque shaft also allows the plane of the curved end to be rotated to facilitate accurate positioning of the catheter end at the desired site. Three curve type configurations named "D", "F" and "J" are available. The electrode assembly 15 is used to deliver ablation energy from the ablation generator 50 to the desired ablation site. The electrode assembly 15 and the ring electrode can be made of precious metals. In some examples, the catheter 14 may also include six thermocouple temperature sensors embedded in the 3.5 mm end electrode 15.

FIG. 3 is a schematic cross-sectional view of a chamber of the heart 12, showing the flexible deflectable middle section 19 of the catheter 14 inside the heart. The catheter 14 is typically inserted into the heart via the skin through a blood vessel (such as the vena cava or the aorta), and then inserted via the septum to reach the endocardial heart chamber. The electrode 15 on the distal end 28 of the catheter engages the endocardial tissue 31. The pressure applied by the distal end to the endocardium deforms the endocardial tissue locally, so that the electrode 15 contacts the tissue over a relatively large area. In the illustrated example, the electrode 15 engages the endocardium at an angle, rather than head-on. Therefore, the distal end 28 is bent relative to the deflectable middle section 19 of the catheter at the elastic joint 33. Such a bend is conducive to optimal contact between the electrode and the endocardial tissue.

Due to the elastic quality of the joint 33, the bend angle of the joint is generally proportional to the pressure applied by the tissue 30 on the distal tip 28 (or in other words, the pressure applied by the distal tip on the tissue). Therefore, the measurement of the bend angle gives an indication of this pressure. This pressure indication can be used by the operator of the catheter 14 to ensure that the distal tip is pressed firmly enough against the endocardium to obtain the desired treatment or diagnostic result, but not too hard to avoid causing undesirable tissue damage. U.S. Patent Nos. 8,357,152, 9,492,639 and 10,688,278 describe a system that uses a pressure sensing catheter in this manner, and the disclosures of these patents are incorporated herein by reference. The catheter 14 can be used in such a system.

The ablation energy generator 50 can generate radio frequency (RF) current according to known RF generators such as disclosed in U.S. Patent No. 5,906,614 and U.S. Patent No. 10,869,713, which discloses a high-power RF generator, and the disclosures of these two patents are incorporated herein by reference. The RF current forms an ablation lesion through a thermal process. RF ablation increases tissue temperature and destroys cells by heating. In addition, the ablation energy generator 50 can also generate a pulsed field (PF) current to form an ablation lesion using irreversible electroporation (IRE). IRE is primarily a non-thermal process that destroys cells by destroying cell membranes. Discussion of a dual-mode ablation energy generator 50 capable of generating RF signals and PF signals can be found in U.S. Publication No. 2021/0161592. U.S. Publication No. 2021/0161592 also discusses the combined use of PF ablation and RF ablation, and the patent is incorporated herein by reference, with a copy provided in the Appendix.

The use of the ablation energy generator 50 and the end effector discussed above can be used in a method of using RF and PF signals to increase the formation of ablation lesions. These ablation lesions are formed in the patient's tissue and, in one example, are used in a pulmonary vein isolation technique.

The depth of the ablation lesion formed by typical RF ablation in the tissue is about 3 mm to about 5 mm. An example of the parameters for forming the RF ablation lesion is to set the power of the RF signal to about 1 watt to about 400 watts. In addition, the RF signal is maintained for about 1 second to about 60 seconds.

Given that RF ablation uses heat to damage tissue, the RF signal typically produces a temperature change in the tissue of about 20°C to about 70°C above body temperature.

Typical PF differs from RF ablation in that at least the temperature change produced by the PF signal is only a few degrees. PF typically forms a lesion in the patient's tissue that is between about 4 mm and about 6 mm in size. To form the lesion, the voltage of the PF signal is set to about 800 volts to about 3000 volts. In addition, the PF signal is typically generated using a specific waveform.

However, one aspect of the present invention uses both RF signals and PF signals on the same portion of tissue to form larger (i.e., deeper) ablation lesions than the RF signal or PF signal alone can produce. Figures 4A and 4B show tissues treated using an example of the present invention. The light/white tissue is an RF ablation lesion 402. In this example, an RF ablation lesion is formed by generating an RF signal with a power of approximately 50 W and a duration of approximately 10 seconds. The RF ablation signal forms an ablation lesion with a specific depth 404. The PF signal is then applied to the same location on the tissue. The PF signal results in the formation of a PF ablation lesion 406. This is shown by the darker tissue surrounding the RF ablation lesion 402. The PF signal is generated using a standard PF protocol, as described in U.S. Patent Publication No. 2021/0161592.

Applying the PF signal to the same location as the location where the RF signal was applied creates a combined lesion. A combined lesion depth 410 is formed by the RF lesion 402 and the PF lesion 406. The combined lesion depth or depth 410 is greater or deeper than the RF lesion depth 404 or the PF lesion depth 408. The combined lesion depth 410 may be approximately 20% to about 40% greater than the RF lesion depth 404 and the PF lesion depth 408. One consideration for this surprising result is that the RF signal "primes" or "prepares" the non-ablated tissue surrounding the RF ablation area 402, allowing the PF signal to penetrate deeper into the tissue. This priming may weaken cells in the area below the area 402, so that the PF ablation signal may form a deeper lesion 408. In contrast, applying the PF signal first may disrupt the voltage difference in the cell wall, allowing the lesion to be just as deep when the RF signal is applied. Both the PF signal and the RF signal may also be applied simultaneously to achieve substantially the same lesion depth. It should be noted here that for ease of measurement, the ablation lesion "depth" (the maximum range measured from the electrode contact point to the deep inside of the incised tissue) is measured to the maximum depth, but the average depth can also be used to quantify the ablation effect of each ablation modality.

To date, we have designed an ablation system for electrophysiological ablation that provides a combined ablation lesion depth via two different energy modalities: (a) an alternating current (AC) signal generator configured to provide a radio frequency signal at high power; and (b) a direct current (DC) signal generator configured to provide high voltage pulses. The system also includes a catheter having an end effector electrically coupled to the AC signal generator and the DC signal generator. The end effector may have at least one electrode disposed on the end effector so that the electrode delivers a high voltage pulse from the at least one electrode to an organ tissue within a patient's body, to a first return electrode and a second return electrode coupled to the outside of the patient's body, and to deliver an RF signal between the at least one electrode and one of the first return electrode or the second return electrode to one of the first return electrode or the second return electrode. The RF signal and the high voltage pulse may be applied to the organ tissue sequentially or simultaneously.

In an example, an end effector may have a cylindrical member having a distal tip electrode and irrigation ports disposed on the cylindrical member to provide irrigation fluid proximate the distal tip electrode.

Another example may have a distal tip electrode coupled to a force sensor. In addition, the RF signal may be applied with a contact force of about 5 grams or more. In addition, the RF signal may be provided with a power of at least 25 watts (up to 400 watts) at a frequency of about 350 kHz to about 500 kHz. The RF signal may also include a frequency of 350 kHz to about 500 kHz, and the RF signal may be provided for a duration of at least 1 second to about 240 seconds.

For other examples, the high voltage pulses may include an amplitude of at least 800V to about 3000V. In addition, the duration of each high voltage pulse may be less than 20 microseconds and provide a pulse train of about 100 microseconds. A time gap selected from any value of 0.3 milliseconds to 1000 milliseconds may be provided between adjacent pulse trains. These pulse trains may provide PF bursts. The PF burst may have any value between 2 pulse trains and 100 pulse trains, wherein the duration of the PF burst includes any value selected from 0 milliseconds to 500 milliseconds. In addition, the high voltage pulses may provide about 60 joules or less.

In view of the systems and disclosures provided herein, we have devised a method 500 for ablating tissue using the present invention, as shown in FIG5 . The method 500 may include positioning an electrode in contact with the tissue (step 502 ). Once in contact, the method 500 may include applying a first ablation signal to the tissue using the electrode (step 504 ). In one example, the first ablation signal may be an RF ablation signal. However, in other examples, a PF ablation signal may be the first ablation signal. The first ablation signal may form a first ablation lesion including a first depth, and may produce a first temperature change in the tissue.

A second ablation signal may be applied to the tissue using the electrode to form a second ablation lesion in the tissue (step 506). In an example, the second ablation signal may be different from the first ablation signal. The second ablation lesion may be formed to have a second size. The second ablation signal may produce a second temperature change in the tissue that differs from the first temperature change by at least 10°C. As above, if the RF signal is the first signal, the PF signal may be the second signal, and when the PF signal is the first signal, the RF signal may be the second signal. In the case where RF ablation causes a temperature change of the tissue greater than 20°C, the temperature change caused by PF is only a few degrees.

Alternatively, a first lesion may be formed with little or no first temperature change in the temperature of the tissue, and a second lesion may be formed by creating a second temperature change in the tissue that differs by at least 10° C. from the first temperature change.

The method may include 500 forming a combined ablation lesion (step 508), which may be caused by applying a first ablation signal and a second ablation signal. A deeper/larger combined ablation lesion may be formed by a combination of a first ablation lesion and a second ablation lesion having a combined size. The combined depth may be approximately 20% to approximately 40% greater than either of the first depth and the second size. In addition, the method 500 may include sequentially applying the first ablation signal and the second ablation signal. This may include first applying the RF signal and then applying the PF signal, or vice versa. However, given that the RF signal may be generated using an alternating current (AC) and the PF signal may be generated using a direct current (DC), another example may cause the two signals to be generated simultaneously or at least have some overlap in the application of the RF signal and the PF signal. In addition, it is known that the contact force between the tissue and the electrode is a factor in the effectiveness of forming the ablation lesion. In one example, the contact force may be from about 5 grams to about 40 grams.

Although the present disclosure is described as being applicable to a catheter 14 having a terminal electrode 15 as shown and described with respect to FIGS. 2A to 3 , the disclosed technology is not limited thereto and may be applicable to catheters having other configurations. For example, the disclosed technology may be applicable to: a basket-shaped catheter 600A (as shown in FIG. 6A and as described in U.S. Provisional Patent Application No. 63/336,094, which is incorporated herein by reference); a circular catheter 600B having a circular region substantially transverse to the longitudinal axis of the catheter (as shown in FIG. 6B and as described in U.S. Provisional Patent Application No. 63/220,312, which is incorporated herein by reference); and a planar array catheter 600C having a planar array of electrodes (as shown in FIG. 6C and as described in U.S. Patent Publication No. 2021/0369338). In addition, the disclosed technology may be applicable to catheters with or without the ability to deliver irrigation to an area proximal to the electrode. In addition, the disclosed technology may be applicable to catheters with force sensors and catheters without force sensors, wherein the force sensor is configured to detect a force applied to the distal end of the catheter. In other words, the disclosed technology is applicable to a range of catheters having electrodes configured to ablate tissue.

FIG. 6A is a perspective view of a basket catheter 600A having a basket electrode assembly 610 attached to the distal end of a deflectable intermediate section 619. The basket electrode assembly 610 may include a plurality of spines 622, each of which has one or more electrodes 626 attached thereto. The electrodes 626 may be configured for mapping and/or ablation. For example, the electrodes 626 may be configured to deliver RF energy or PF energy to ablate tissue according to the techniques described herein. As will be appreciated, by using the basket electrode assembly 610 to deliver RF energy or PF energy, the disclosed techniques may be configured to ablate a larger area of tissue than the tip electrode 15 described with respect to FIGS. 2A to 3 . In some examples, selected electrodes 626 on the basket electrode assembly 610 may be energized to ablate selected areas of tissue contacted by the basket electrode assembly 610, enabling the physician 24 to better control the basket electrode assembly 610.

6B is an illustration of a profile view of a circular catheter 600B having a circular region 630 attached to a deflectable intermediate section 619. The circular region 630 is disposed substantially orthogonal to a longitudinal axis passing through the distal end of the deflectable intermediate section 619. The circular region 630 is preferably substantially perpendicular to the catheter body and forms a flat circle, or may be slightly spiral, as shown in FIG6B .

The circular area 630 includes electrodes 626 distributed around its circumference. The electrodes 626 can be configured for mapping and/or ablation. During an exemplary treatment in which the electrodes 626 are used to ablate tissue, the electrodes 626 can be configured to deliver RF energy and PF energy to ablate tissue according to the techniques disclosed herein. When the diameter of the circular main area corresponds roughly to the diameter of the pulmonary vein or the coronary sinus, the depth of the roughly circular area 630 can allow ablation of tissue along the diameter of the pulmonary vein or other tubular structures of or near the heart 12. The circular arrangement of the electrodes 626 facilitates the formation of a circular or annular ablation lesion to interrupt the electrical activity through the circumference of the tubular body structure, thereby electrically isolating the tubular structure from the tissue on the opposite side of the annular ablation lesion. In other examples, each electrode 626 can be energized separately to provide RF ablation or PF ablation only at a selected portion of the tissue.

Fig. 6C shows a planar array catheter 600C, which has a plurality of ridges 622 arranged in a plane and attached to the distal end of a deflectable intermediate section 619. Each ridge 622 has one or more electrodes 626 disposed thereon. Each electrode 626 can be configured for mapping and/or ablation. For example, electrode 626 can be configured to deliver RF energy or PF energy to ablate tissue according to the technology described herein. By arranging electrodes 626 into a planar array along ridge 622, planar array catheter 600C can be configured to facilitate ablation of tissues with a larger area than the distal electrode 15 described in relation to Fig. 2 A to Fig. 3. In some examples, the selected electrode 626 on the planar array catheter 600C can be energized to ablate the selected area of the tissue contacted by the electrode 626 so that the physician 24 can better control the planar array catheter 600C.

As will be appreciated, the method 500 described herein may vary according to the various elements and examples described herein. That is, the method according to the disclosed technology may include all or some of the steps described above, and/or may include additional steps not explicitly disclosed above. Certain steps may be performed sequentially or simultaneously. In addition, the method according to the disclosed technology may include some of the specific steps described above, but not all of the specific steps. In addition, the various methods described herein may be combined in whole or in part.

Although the present disclosure has been described in conjunction with a plurality of exemplary aspects as shown in the accompanying drawings and as described above, it should be understood that other similar aspects may be used, or the described aspects may be modified and added without departing from the present disclosure to perform the same functions of the present disclosure. For example, in various aspects of the present disclosure, methods and components are described according to various aspects of the subject matter disclosed in the present invention. However, the teachings herein also contemplate other methods or components equivalent to these described aspects. Therefore, the present disclosure should not be limited to any single aspect, but should be interpreted in terms of breadth and scope according to the appended claims.

Claims (14)

1. An ablation system for electrophysiological use, the system comprising:

An Alternating Current (AC) signal generator configured to provide a radio frequency signal at high power;

A Direct Current (DC) signal generator configured to provide a high voltage pulse; and

A catheter having an end effector electrically coupled to the AC signal generator and the DC signal generator, the end effector including at least one electrode disposed on the end effector such that the at least one electrode delivers the high voltage pulse from the at least one electrode to organ tissue within a patient, to first and second return electrodes coupled to the patient's body, and the radio frequency signal between the at least one electrode and one of the first or second return electrodes;

Wherein the at least one electrode is configured to deliver the high voltage pulse and the radio frequency signal to tissue to form a combined ablation focus in the tissue such that the combined ablation focus is at least 20% larger than an ablation focus formed by the same radio frequency signal alone or by the same high voltage pulse alone.

2. The ablation system of claim 1, wherein the radio frequency signal and the high voltage pulse are applied to the organ tissue sequentially or simultaneously.

3. The ablation system of any of the preceding claims, wherein the end effector comprises a cylindrical member having a distal tip electrode and an irrigation port disposed on the cylindrical member to provide irrigation fluid proximate the distal tip electrode.

4. The ablation system of any of the preceding claims, wherein the distal tip electrode is coupled to a force sensor.

5. The ablation system of any of the preceding claims, wherein the radio frequency signal is applied with a contact force of about 5 grams or greater.

6. The ablation system of any of the preceding claims, wherein the radio frequency signal is provided with a power of at least 25 watts.

7. The ablation system of any of the preceding claims, wherein the radio frequency signal comprises a frequency of 350kHz to about 500kHz and the radio frequency signal is provided for a duration of at least 1 second.

8. The ablation system of any of the preceding claims, wherein the high voltage pulse comprises an amplitude of at least 800V.

9. The ablation system of any of the preceding claims, wherein each of the high voltage pulses has a duration of less than 20 microseconds.

10. The ablation system of any of the preceding claims, wherein the plurality of high voltage pulses provide a pulse train of about 100 microseconds.

11. The ablation system of any of the preceding claims, wherein a time gap of any value selected from 0.3 milliseconds to 1000 milliseconds is provided between adjacent bursts.

12. The ablation system of any of the preceding claims, wherein the plurality of pulse trains provides PF bursts.

13. The ablation system according to any of the preceding claims, wherein the PF burst comprises any value between 2 bursts and 100 bursts, wherein the duration of the PF burst comprises any value selected from 0 milliseconds to 500 milliseconds.

14. The ablation system of any of the preceding claims, wherein the high voltage pulse provides about 60 joules or less.