Focal pulsed field ablation device and method

Abstract

Devices, systems and methods for more effectively using pulsed field ablation energy to ablate tissue while minimizing collateral damage to non-target tissue. In one embodiment, a system for ablating tissue at a treatment site includes: an energy delivery device; and a control unit including: an impedance-modifying fluid source in fluid communication with the energy delivery device; an energy generator in electrical communication with the energy delivery device and configured to transmit energy to the energy delivery device, and the energy delivery device is configured to deliver energy to the treatment site; and a processing circuit system configured to control the delivery of an impedance-modifying fluid from the energy delivery device to the treatment site. In one embodiment, a method for ablating tissue includes delivering an impedance-modifying fluid to the treatment site and delivering pulsed field ablation energy to the treatment site.

Description

Technical Field

[0001] The present technology generally relates to devices, systems and methods for more effectively using pulsed field ablation energy to ablate tissue while minimizing collateral damage to non-target tissue. In one embodiment, a system for ablating tissue at a treatment site includes: an energy delivery device; and a control unit including: an impedance-modifying fluid source in fluid communication with the energy delivery device; an energy generator in electrical communication with the energy delivery device and configured to transmit energy to the energy delivery device, and the energy delivery device is configured to deliver energy to the treatment site; and a processing circuit system configured to control the delivery of the impedance-modifying fluid from the energy delivery device to the treatment site. Background Art

[0002] Tissue ablation is a medical procedure commonly used to treat diseases such as cardiac arrhythmias, including atrial fibrillation. To treat cardiac arrhythmias, ablation may be performed to modify tissue, such as to block abnormal electrical propagation through cardiac tissue and / or interrupt abnormal electrical conduction through cardiac tissue. Although thermal ablation techniques, such as cryoablation and radiofrequency (RF) ablation, are often used, non-thermal techniques, such as pulsed field ablation (PFA), may also be used.

[0003] Pulsed field ablation involves the application of a short pulsed electric field (PEF), which can reversibly or irreversibly destabilize cell membranes by electroosmosis, but does not generally affect the structural integrity of tissue components (including acellular cardiac extracellular matrix). The properties of PFA allow for very short periods of therapeutic energy delivery, with a duration of about tens of milliseconds. In addition, PFA may not cause collateral damage to non-target tissues as frequently or severely as thermal ablation techniques. Additionally, it is preferred that drug preparations be introduced into cells of target tissues exposed to PEFs with reversible membrane penetration.

[0004] Pulsed electric field ablation therapy can be safely delivered from almost any intracardiac device electrode or electrode group, assuming that the (multiple) electrodes have sufficient surface area and inter-electrode spacing to avoid local heating when delivered in a bipolar manner between the electrodes. Devices such as irrigation catheters can be used to deliver pulsed electric field energy, but they generally have relatively small surface areas. High energy levels can also increase the risk of thromboembolic events. Further, at least some of the delivered pulsed field ablation energy may be unexpectedly directed toward non-target tissues. For example, even when (multiple) electrodes are in contact with target tissue, at least some of the delivered energy will be transferred into the blood pool instead of into the target tissue. When high voltages are applied to electrodes in a blood-tissue environment, such as when attempting to create deep damage in cardiac muscle, relatively high currents can be driven into both the blood and the target tissue. If such currents are above the threshold at which a large amount of heat is generated at the blood-electrode junction, undesirable release of bubbles and hemolysis may occur. These bubbles and / or heat-denatured blood proteins may be released as embolic emboli that are harmful to the patient. Summary of the invention

[0005] The technology disclosed herein generally relates to devices, systems, and methods for more effectively using pulsed field ablation energy to ablate tissue while minimizing the total energy delivered and collateral damage to non-target tissue. In one embodiment, a system for ablating tissue at a treatment site includes: an energy delivery device; and a control unit including: an impedance-modifying fluid source, the impedance-modifying fluid source being in fluid communication with the energy delivery device; an energy generator, the energy generator being in electrical communication with the energy delivery device and being configured to transmit energy to the energy delivery device, and the energy delivery device being configured to deliver energy to the treatment site; and a processing circuit system, the processing circuit system being configured to control the delivery of the impedance-modifying fluid from the energy delivery device to the treatment site.

[0006] In one aspect of this embodiment, the processing circuit system is configured to control the delivery of an impedance modifying fluid from the energy delivery device, thereby causing the energy delivery device to deliver the impedance modifying fluid to the treatment site before starting to deliver energy from the energy delivery device to the treatment site. In one aspect of this embodiment, the energy delivery device delivers the impedance modifying fluid to the treatment site at a flow rate between about 1 mL / min and about 120 mL / min (about 2 mL / sec). In one aspect of this embodiment, the energy delivery device delivers the impedance modifying fluid to the treatment site about two seconds before starting to deliver energy from the energy delivery device to the treatment site.

[0007] In one aspect of this embodiment, the processing circuitry is configured to control delivery of the impedance modifying fluid from the energy delivery device, thereby causing the energy delivery device to deliver the impedance modifying fluid to the treatment site simultaneously with initiating delivery of energy from the energy delivery device to the treatment site.

[0008] In one aspect of this embodiment, the impedance modifying fluid is a hypotonic fluid. In one aspect of this embodiment, the hypotonic fluid is a physiological saline solution comprising less than 0.9% by weight sodium chloride.

[0009] In one embodiment, the hypotonic fluid comprises at least one of glucose, dextrose, calcium, calcium gluconate, and calcium chloride.

[0010] In one aspect of this embodiment, the impedance modifying fluid is a hypertonic fluid.

[0011] In one aspect of this embodiment, the energy delivery device comprises at least one flushing port in fluid communication with a source of impedance-modifying fluid. In one aspect of this embodiment, the energy delivery device further comprises at least one energy delivery electrode, the at least one flushing port satisfying at least one of the following: in the at least one energy delivery electrode, and in close proximity to the at least one energy delivery electrode.

[0012] In one aspect of this embodiment, each of the at least one energy delivery electrode has a first edge and a second edge opposite the first edge, and at least one irrigation port in the energy delivery electrode is proximate to at least one of the first edge and the second edge.

[0013] In one aspect of this embodiment, the energy delivery device further comprises an electrode carrying structure to which the at least one energy delivery electrode is coupled, and in which the at least one irrigation port is located.

[0014] In one aspect of this embodiment, the impedance modifying fluid source is a first impedance modifying fluid source, the control unit further comprises a second impedance modifying fluid source in fluid communication with the energy delivery device. In one aspect of this embodiment, the first impedance modifying fluid is a hypotonic fluid, and the second impedance modifying fluid is a hypertonic fluid, the processing circuit system is configured to control delivery of the first impedance modifying fluid and the second impedance modifying fluid from the energy delivery device, thereby causing the energy delivery device to simultaneously deliver the first impedance modifying fluid to a first portion of the treatment site and the second impedance modifying fluid to a second portion of the treatment site.

[0015] In one aspect of this embodiment, the first impedance-modifying fluid is a hypotonic fluid and the second impedance-modifying fluid is a hypertonic fluid, the energy delivery device is configured to deliver the first impedance-modifying fluid and the second impedance-modifying fluid together as a mixture, and the processing circuit system is configured to modify the amount of at least one of the first impedance-modifying fluid and the second impedance-modifying fluid to change the mixture at least one of before or during delivery of energy from the energy delivery device.

[0016] In one embodiment, a method for ablating tissue includes delivering an impedance modifying fluid to a treatment site and delivering pulsed field ablation energy to the treatment site.

[0017] In one aspect of this embodiment, the treatment site includes a region of target tissue and blood in contact with the region of target tissue, pulsed field ablation energy is delivered to the region of target tissue and an impedance modifying fluid is delivered to the blood.

[0018] In an aspect of this embodiment, an impedance modifying fluid is delivered to the blood immediately prior to delivering pulsed field ablation energy to the region of target tissue.

[0019] In one aspect of this embodiment, an impedance modifying fluid is delivered to the blood simultaneously with delivering pulsed field ablation energy to a region of target tissue.

[0020] In one aspect of this embodiment, the treatment site includes a region of epicardial tissue and a pericardial space in contact with the region of epicardial tissue, pulsed field ablation energy is delivered to the region of epicardial tissue and an impedance modifying fluid is delivered to the pericardial space.

[0021] In one embodiment, a tissue ablation device includes: an elongated body having a distal portion and a proximal portion opposite the distal portion, the distal portion including a distal end; an energy delivery electrode located at the distal portion of the elongated body; an energy return electrode on the elongated body, proximal to the energy delivery electrode, the energy return electrode having a first outer diameter; and a distance keeping element on the elongated body, close to the energy return electrode, the distance keeping element having a second outer diameter greater than the first outer diameter.

[0022] In one aspect of this embodiment, the distance-keeping element is made of a non-conductive material.

[0023] In an aspect of this embodiment, the distance-keeping element is at least one of a fin, a ring, and a spline.

[0024] In one aspect of this embodiment, the distance keeping element is convertible between a delivery configuration and an expanded configuration, and when the distance keeping element is in the expanded configuration, the distance keeping element has a second outer diameter. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] A more complete understanding of the present invention, together with attendant advantages and features thereof, will be more readily appreciated by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which:

[0026] Figure 1 An exemplary delivery of pulsed field ablation energy to tissue as known in the art is shown;

[0027] Figure 2 An exemplary delivery of pulsed field ablation energy together with an impedance modifying fluid is shown;

[0028] Figure 3 An exemplary medical system for delivering pulsed field ablation energy with an impedance modifying fluid is shown;

[0029] Figure 4 A first configuration of a portion of a medical device for delivering pulsed field ablation energy and an impedance modifying fluid is shown;

[0030] Figure 5 A second configuration of a portion of a medical device for delivering pulsed field ablation energy and an impedance modifying fluid is shown;

[0031] Figure 6 A third configuration of a portion of a medical device for delivering pulsed field ablation energy and an impedance modifying fluid is shown;

[0032] Figure 7 A fourth configuration of a portion of a medical device for delivering pulsed field ablation energy and an impedance modifying fluid is shown;

[0033] Figure 8 A fifth configuration of a portion of a medical device for delivering pulsed field ablation energy and an impedance modifying fluid is shown;

[0034] Fig. 9 A sixth configuration of a portion of a medical device for delivering pulsed field ablation energy and an impedance modifying fluid is shown;

[0035] Fig.10 A seventh configuration of a portion of a medical device for delivering pulsed field ablation energy and an impedance modifying fluid is shown;

[0036] Fig.11 A portion of a medical device for ablating tissue using pulsed field ablation energy and delivering a first impedance modifying fluid and a second impedance modifying fluid is shown;

[0037] Fig.12 Shown for use with Fig.12 An exemplary medical system for use with a device of the type described herein, the medical system comprising a first fluid reservoir containing a first impedance modifying fluid and a second fluid reservoir containing a second impedance modifying fluid;

[0038] Fig.13 The use of an energy delivery device, such as a pulsed field ablation device, and an energy return electrode known in the art to heal tissue is shown;

[0039] Fig.14The use of an energy delivery device (such as a pulsed field ablation device) and an energy return electrode and the use of an impedance modifying fluid to heal tissue is shown;

[0040] Fig.15 Exemplary placement of energy delivery devices and secondary devices relative to myocardial tissue is shown;

[0041] Fig.16 A first embodiment of an energy delivery device is shown, the device comprising at least one energy return electrode and at least one distance maintaining element;

[0042] Fig.17 A second embodiment of an energy delivery device is shown, the device comprising at least one energy return electrode and at least one distance keeping element; and

[0043] Fig.18 A third embodiment of an energy delivery device is shown, the device comprising at least one energy return electrode and at least one distance keeping element. DETAILED DESCRIPTION

[0044] Before describing the exemplary embodiments in detail, it should be noted that the embodiments reside primarily in the combination of device components and processing steps related to ablating tissue. Therefore, the components of the system and method have been represented at appropriate locations by conventional reference numerals in the drawings, which only show those specific details that are relevant to understanding the embodiments of the present disclosure so as not to obscure the disclosure with details that are obvious to those skilled in the art having the benefit of the description herein.

[0045] As used herein, the term "pulsed field ablation" (PFA) or "pulsed field ablation energy" refers to a form of electrical energy delivery that generates tissue damage through the mechanism of irreversible electroporation (IRE). The electric field gradient generated by applying a high voltage to a single or multiple electrodes surrounds those electrodes to a degree exceeding the size of those electrodes, penetrating into the surrounding tissue to damage cell membranes through the process of IRE. Tissue exposed to a PFA electric field gradient at or above the IRE threshold will form damage, while tissue exposed to a field gradient below the IRE threshold will survive. This type of PFA delivery is expected to produce a high electric field gradient with minimal current, so that the delivered current is not enough to cause a large amount of heat in the surrounding tissue. The devices, systems and methods disclosed herein minimize the excess current delivered during the application of high voltage PFA.

[0046] As used herein, relational terms such as "first" and "second", "top" and "bottom", etc., may be used solely to distinguish one entity or element from another entity or element, without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the concepts described herein. The singular forms "a", "an", and "the" used herein are also intended to include the plural forms, unless the context clearly indicates otherwise. It will be further understood that when used herein, the terms "comprises", "comprising", "includes", and / or "including" specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0047] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by ordinary technicians in the field to which the present disclosure belongs. It will be further understood that the terms used herein should be interpreted as having the meaning consistent with their meaning in the context of this specification and the relevant technology, and unless explicitly stated herein, will not be interpreted as idealized or overly formal meanings.

[0048] In the embodiments described herein, "in communication with" and other connection terms may be used to indicate electrical or data communication, which may be accomplished by, for example, physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling, or optical signaling. Those skilled in the art will appreciate that the various components may interoperate, and modifications and variations may be possible to achieve electrical and data communication.

[0049] Reference now Figure 1 and Figure 2 , showing an exemplary delivery of pulsed field ablation energy. Figure 1 The delivery of pulsed field ablation energy 10 to an area of ​​tissue 12 as known in the art is shown. Specifically, at least a portion of a medical device 14, such as a portion of an energy delivery device 14 including one or more electrodes 16, is placed near or in contact with an area of ​​tissue 12. The pulsed field ablation energy 10 is delivered from the electrode(s) 16 to the tissue 12, but is also delivered to the blood 18 surrounding the tissue. The delivery of the pulsed field ablation energy 10 to the tissue 12 results in ablation lesions 20, but the delivery of the pulsed field ablation energy 10 to the blood 18 may result in the formation of gas bubbles, hemolysis, and / or heat-denatured blood proteins 22.

[0050] on the contrary, Figure 2The delivery of pulsed field ablation energy 10 and impedance modifying fluid 24 to a region of tissue 12 is shown. Figure 1 As in the delivery of pulsed field ablation energy 10, at least a portion of a medical device 26, such as a portion of an energy delivery device 26 including one or more electrodes 28, is placed near or in contact with an area of ​​tissue 12. However, just prior to and / or during the delivery of pulsed field ablation energy 10, a bolus or volume of an impedance-modifying fluid 24 is injected from one or more flush ports 30 in the energy delivery device 26. In one embodiment, the impedance-modifying fluid 24 is a hypotonic fluid that briefly increases the electrical impedance of the blood 18 environment surrounding the (multiple) electrodes 28 to a level that reduces the current delivered through the blood 18, thereby reducing or eliminating local heating of the blood. By reducing the current delivered to the blood, the current intensity on the non-blood (i.e., tissue) side of the electrode 28 can be slightly higher because there is less electrode surface area for voltage to pass through to drive the current. Thus, the current that would otherwise be delivered to the blood (wasted current) is minimized, thereby allowing most of the current to be directed to the myocardium, i.e., the intended ablation target. This can also limit the total amount of hemolysis in the blood, bubbles generated by electrolysis, and / or coagulation of the blood, even during the creation of deep lesions. In addition, the use of the impedance-modifying fluid 24 helps focus the pulsed field ablation energy 10 only toward the target tissue 12, and thereby obtains more effective lesion formation, and / or helps form deeper lesions 36 compared to lesions 34 created using a technique that does not utilize the impedance-modifying fluid 24. When delivering a series of rapid high-voltage pulses, delivering the impedance-modifying fluid 24 immediately before and / or during the delivery of the pulsed field ablation energy 10 may be particularly useful. However, the method is not limited to pulsed field ablation, as it also has some advantages in the case of delivering conventional radiofrequency energy for tissue hyperthermia ablation. However, in another embodiment, the impedance-modifying fluid 24 is a hypertonic fluid that temporarily reduces the electrical impedance of the blood 18 environment around the (multiple) electrodes 28 to a level that increases the current delivered through the blood 18. Alternatively, both hypotonic and hypertonic fluids may be used.

[0051] Reference now Figure 3 , Figure 3An exemplary medical system for delivering pulsed field ablation energy and impedance-modifying fluid is shown. In one embodiment, the medical system 38 generally includes a medical device 26 (such as an energy delivery device 26) having one or more electrodes 28 and one or more flushing ports 30, and a control unit 40 in communication with the energy delivery device 26. The energy delivery device 26 can be used to deliver both impedance-modifying fluid 24 and pulsed field ablation energy 10 (and / or other types of energy or thermal treatment). The medical system 38 may additionally include one or more secondary devices 42, such as a secondary device 42 having one or more energy return electrodes 44 (e.g., such as a Fig.13 and Fig.14 ).

[0052] The control unit 40 includes one or more system components for delivering, controlling, and monitoring ablative energy and impedance-modifying fluid 24. The control unit 40 may be configured for use with one or more ablative energy modalities other than non-thermal pulsed field ablation, such as radiofrequency ablation, laser ablation, microwave ablation, cryoablation, and the like. In one embodiment, the control unit 40 includes an energy generator 46 for delivering pulsed field ablation energy 10 for irreversibly and / or reversibly electroporating tissue 12. The energy generator 46 communicates with the energy delivery device 26 so that energy is delivered from the energy generator 46 through one or more electrodes 28. The control unit 40 may further include one or more controllers, processors, and / or software modules that contain instructions or algorithms to provide automatic operation and execution of the features, sequences, or processes described herein. For example, in one embodiment, the control unit 40 includes a processing circuit system 48 having a memory and a processor. The memory is in electrical communication with the processor and includes instructions that, when executed by the processor, configure the processor to receive, process, or otherwise use signals from the energy delivery device and / or other system components. The processing circuit system 48 may further include at least one timing circuit for controlling the delivery of the impedance-modifying fluid 24 (e.g., for timing the delivery of the impedance-modifying fluid 24 relative to the delivery of the pulsed field ablation energy 10). Still further, the control unit 40 may include one or more user input devices, controllers, and / or displays (which, for simplicity, may each be generally referred to as a user input device 50) for collecting and transmitting information from and to a user.

[0053] Medical system 38 is configured to deliver at least irreversible electroporation energy (pulsed field ablation energy), and may also be optionally configured for use with other energy modalities, such as laser ablation, irreversible electroporation, cryoablation, microwave ablation, thermal radiofrequency ablation, and the like. Electroporation is a phenomenon that causes cell membranes to become "leaky" (i.e., permeable to molecules that would otherwise not permeate or semi-permeate the cell membrane). Electroporation, which may also be referred to as electropermeabilization, pulsed electric field therapy, non-thermal irreversible electroporation, irreversible electroporation, high-frequency irreversible electroporation, nanosecond electroporation, or nanoelectroporation, involves the application of high amplitude pulses to cause physiological modifications (i.e., permeabilization) of cells of tissues to which energy is applied. These pulses may preferably be shorter (e.g., nanosecond, microsecond, or millisecond pulse widths) to allow application of high voltage, high current (e.g., 20 amps or more) without the (multiple) longer durations of current flow that would otherwise cause significant tissue heating and muscle stimulation. The pulsed electrical energy can induce the formation of microscopic defects that lead to hyperpermeabilization of the cell membrane. Depending on the characteristics of the electric pulse, the electroporated cells can survive the electroporation, which is called "reversible electroporation", or the electroporated cells die, which is called "irreversible electroporation" (IRE). Reversible electroporation can be used to transfer agents including genetic materials and other macromolecules or small molecules into target cells for various purposes, including changing the action potential of cardiac muscle cells.

[0054] The energy generator 46 can deliver electrical pulses to the energy delivery device 26 to perform an electroporation procedure to cardiac tissue or other tissues in the patient's body (such as renal tissue, airway tissue, and organs or tissues within the cardiac interstitial or pericardial spaces). Specifically, the energy generator 46 can be configured and programmed to deliver a pulsed high voltage electric field (referred to as "pulsed field ablation" or "pulsed electric field ablation") and / or pulsed radiofrequency ablation suitable for achieving the desired pulsed high voltage ablation. As a reference point, the non-radio frequency pulsed high voltage ablation effect of the present disclosure can be distinguished from DC current ablation, and thermal induced ablation accompanied by traditional RF technology. For example, the pulse sequence delivered by the energy generator can be delivered at a frequency of less than 30kHz, and in an exemplary configuration, at a frequency of 1kHz (which is a lower frequency than radiofrequency treatment). For the purpose of completely blocking abnormal conduction paths along or through cardiac tissue, destroying the ability of the cardiac tissue so ablated to propagate or conduct cardiac depolarization waveforms and associated electrical signals, the pulsed field energy according to the present disclosure can be sufficient to cause cell death. Additionally or alternatively, the energy generator may be configured and programmed to deliver RF energy suitable for achieving tissue ablation.

[0055] Although not shown, the medical system 38 may include one or more sensors for monitoring operating parameters (such as pressure, temperature, delivered voltage, etc.) through the medical system 38, and for measuring and monitoring one or more tissue characteristics (such as EGM waveforms, monophasic action potentials, tissue impedance, etc.), and for monitoring, recording, or otherwise transmitting measurements or conditions of the surrounding environment within the energy delivery device 26 or within other components of the medical system 38 or at a distal portion of the energy delivery device 26. The sensor(s) may communicate with the control unit 40 for initiating or triggering one or more alarms or ablation energy delivery modifications during operation of the energy delivery device 26.

[0056] In one embodiment, the control unit 40 also includes at least one fluid reservoir 52 containing at least one impedance-modifying fluid 24 and at least one pump 54 for delivering the impedance-modifying fluid 24 before and / or during the delivery of the pulsed field ablation energy 10. In one embodiment, the at least one impedance-modifying fluid 24 is a hypotonic (low ionic strength) fluid for directing the electric field during ablation, such as 0.25% saline, 0.45% saline and / or glucose, Dextran-40, Dextran-70, 2.5% dextrose solution, glucose solution, etc. Optionally, the at least one impedance-modifying fluid 24 can be selected so that it matches the osmotic pressure of the blood or is reasonably close to the osmotic pressure of the blood. The at least one pump 54 communicates with the processing circuit system 48 of the control unit 40, and the processing circuit system 48 controls the timing and delivery of the impedance-modifying fluid 24 relative to the delivery of the pulsed field ablation energy 10. In one embodiment, the processing circuit system 48 is configured to time the delivery of the impedance-modifying fluid 24 relative to the delivery of the pulsed field ablation energy 10, such that the processing circuit system 48 instructs the pump 54 to deliver a bolus or volume of the impedance-modifying fluid 24 from the (multiple) flushing ports 30 of the energy delivery device 26 immediately prior to and / or during the delivery of the pulsed field ablation energy 10. In one embodiment, the processing circuit system 48 instructs the pump 54 to deliver the impedance-modifying fluid 24 between about one second and about three seconds of beginning to deliver the pulsed field ablation energy 10. Additionally or alternatively, the processing circuit system 48 instructs the pump 54 to deliver the impedance-modifying fluid 24 during the delivery of the pulsed field ablation energy 10. In one embodiment, upon completion of the pulsed field ablation energy delivery, the delivery of the impedance-modifying fluid 24 is immediately stopped.

[0057] In one embodiment, the control unit 40 is configured to deliver one or more test pulses or a high frequency continuous signal from the electrode(s) 28 of the energy delivery device 26 for measuring the impedance at the electrode(s) 28 after delivering the impedance modifying fluid 24 and before delivering the pulsed field ablation energy 10 to verify that the impedance of the blood tissue environment 18 / 12 surrounding the electrode(s) 28 has been changed by a desired amount to enhance lesion formation and limit embolism formation (such as gas bubbles and / or heat-denatured blood proteins 22). If the control unit 40 (e.g., the processing circuit system 48) determines that the impedance of the blood tissue environment 18 / 12 has been sufficiently changed, the control unit 40 will instruct the energy generator 46 to deliver the pulsed field ablation energy 10 from the electrode(s) 28. On the other hand, if the control unit 40 determines that the impedance of the blood tissue environment 18 / 12 has not been sufficiently changed, the control unit 40 will instruct the pump 54 to deliver another bolus or another volume of the impedance modifying fluid 24. In this case, the control unit 40 will deliver one or more further test pulses before commencing delivery of the pulsed field ablation energy 10 from the energy generator 46.

[0058] The control unit 40 may optionally include at least one fluid recovery reservoir (not shown) for collecting recovered impedance-modifying fluid from the treatment site(s). In this embodiment, the control unit 40 also includes one or more system components for removing fluid and / or other particles from the treatment site. In one embodiment, the control unit 40 includes a fluid removal component (not shown), such as a vacuum pump, a syringe pump, or a vacuum reservoir, which applies suction to one or more fluid exhaust conduits of the energy delivery device 26 (disclosed in more detail below).

[0059] Reference now Figure 4-Figure 10 , shows an embodiment of an energy delivery device 26 for delivering pulsed field ablation energy 10 and an impedance modifying fluid 24. In general, Figure 4-Figure 10 Each of the embodiments includes an energy delivery device 26 having at least one electrode 28 and at least one irrigation port 30. The energy delivery device 26 can be a focal catheter having an elongated body having one or more electrodes 28. Alternatively, the energy delivery device 26 can have any other suitable configuration, including, but not limited to, a device having an expandable treatment element having an electrode array. The (multiple) electrodes 28 are in electrical communication with a control unit 40 (e.g., an energy generator 46 and a processing circuit system 48) for delivering pulsed field ablation energy 10. The (multiple) irrigation ports 30 are connected to the at least one fluid delivery conduit 56 (e.g., such as a Figure 418 ) is in fluid communication with at least one fluid reservoir 52. The flush port(s) 30 may be positioned on the energy delivery device 26 such that when the electrode(s) 28 are in contact with the target tissue, the flush port(s) 30 are oriented away from the target tissue (i.e., facing the blood 18). Additionally or alternatively, the flush port(s) 30 may be selectively operable such that the control unit 40 and / or the user may select from which port(s) 30 the impedance modifying fluid 24 is delivered. Thus, the delivery of the impedance modifying fluid 24 may create a bolus or volume of the impedance modifying fluid 24 opposite the electrode tissue contact location, thereby driving current away from the impedance modifying fluid 24 and toward the target tissue 12. In a similar manner, when the electrode(s) 28 are positioned within the pericardial space and in contact with the epicardial surface of the heart, delivery of an impedance modifying fluid 24 (such as a hypotonic impedance modifying fluid) may be injected into the pericardial space from the flush port(s) 30, thereby driving current into the epicardium of the heart and minimizing current passing into the pericardium and away from the heart. The irrigation port(s) 30 may be designed with an internal fluid manifold having a larger diameter than the more proximal fluid delivery lumen, thereby causing the fluid to exit the electrode(s) 28 at a relatively low pressure, thereby avoiding fluid extrusion from the irrigation port(s) 30 which may become blocked by tissue contact. In one embodiment, the energy delivery device 26 includes one or more chambers 57 within the elongated body and in fluid communication with the fluid delivery conduit 56 and the irrigation port(s) 30, each chamber 57 being located proximal to one or more energy delivery electrodes 28 (e.g., Figure 5 and Figure 6 ). In one embodiment, each chamber 57 provides an increased volume over the fluid delivery conduit 56. Such a configuration ensures that the electrode(s) 28 will maintain firm tissue contact as the impedance-modifying fluid exits the electrode(s) 28 on the tissue-contacting side. For example, it is desirable that the electrode(s) 28 be in firm contact with the tissue to be ablated; however, a high pressure jet of the impedance-modifying fluid 24 may lift the electrode(s) 28 out of contact with the tissue and / or form a layer of low conductivity fluid between the electrode(s) 28 and the target tissue.

[0060] Optionally, at least some of the (multiple) flush ports are in fluid communication with at least one fluid recovery reservoir and fluid removal component via at least one fluid discharge conduit (not shown, but it will be understood that at least one fluid delivery conduit 56 may additionally or alternatively be used as the at least one fluid discharge conduit). In one embodiment, each flush port 30 may selectively be used to deliver or discharge the impedance-modifying fluid 24, and the control unit 40 may be configured to automatically or semi-automatically selectively connect each of the (multiple) flush ports 30 to the pump 54 and the (multiple) fluid reservoirs or fluid removal components and the (multiple) fluid recovery reservoirs. Additionally or alternatively, a user may manually control the function of each flush port 30 (i.e., control whether each flush port 30 is used for fluid delivery or fluid discharge). For simplicity, the energy delivery device 26 shown in the accompanying drawings is described hereinafter as having a flush port 30 for delivering the impedance-modifying fluid 24, but it will be understood that each flush port 30 may additionally or alternatively be used for fluid discharge. In Figure 4-Figure 10 An exemplary configuration of flush port(s) 30 is shown in ; however, flush port(s) 30 are not limited to the configuration shown and may have any suitable size, shape, distribution pattern, location, or other characteristics.

[0061] refer to Figure 4 , the energy delivery device 26 includes an elongated body, rod, carrier arm, or other structure 58 carrying at least one electrode 28 for delivering pulsed field ablation energy 10. Each electrode 28 includes at least one flushing port 30 for delivering impedance-modifying fluid 24. In one embodiment, each flushing port 30 is in fluid communication with at least one fluid reservoir 52 via a fluid delivery conduit 56. Figure 5 , energy delivery device 26 and Figure 4 , but includes at least one flushing port 30 on or near the edge of the (multiple) electrode 28. In one embodiment, at least one flushing port 30 is close to at least one edge of the electrode 28, such as within 0.5 mm. The electric field delivered by the (multiple) electrode 28 can be highly concentrated in these areas, and is therefore a desired goal for minimizing current. The increase in blood impedance around the (multiple) electrode 28 generated by delivering an impedance modifying fluid 24 (such as a hypotonic fluid) reduces the overall current delivered, while maintaining the current passing through the side of each electrode 28 that is in direct contact with the target tissue 12, which has a lower impedance path. As a result, the current is diverted or directed toward the target tissue 12, and away from the blood 18 and non-target tissue. Additionally, bubble formation and / or charring can be minimized or prevented without continuous flushing throughout the duration of energy delivery.

[0062] refer to Figure 6 , the energy delivery device 26 includes an elongated body, rod, carrier arm, or other structure 58 carrying at least one electrode 28 for delivering pulsed field ablation energy 10. Figure 4 and Figure 5 In contrast to the embodiment shown in Figure 6 The embodiment shown in FIG. 5 includes at least one flush port 30 in the electrode-carrying structure 58 rather than on the electrode(s) 28 themselves. In one embodiment, each flush port 30 is in fluid communication with at least one fluid reservoir 52 via a fluid delivery conduit 56 .

[0063] refer to Figure 7 , the impedance-modifying fluid 24 is delivered from the device, rather than directly from the energy delivery device 26. In one embodiment, the impedance-modifying fluid 24 is delivered to the treatment site through the delivery sheath 60 of the energy delivery device 26. Additionally or alternatively, the impedance-modifying fluid 24 may be delivered through a secondary device (not in Figure 7 As shown in , a secondary sheath or secondary medical device) is delivered to the treatment site.

[0064] However, it will be appreciated that combinations of the above may also be used. Figure 8 , the energy delivery device 26 includes a combination of at least one irrigation port 30 in the electrode 28 and an irrigation port 30 in the electrode-carrying structure 58. Alternatively, Figure 8 The energy delivery device 26 shown in FIG. 2 may additionally be used to deliver an impedance-modifying fluid 24 from a delivery sheath 60 and / or a secondary device, such as Fig. 9 In another embodiment, as shown in Fig.10 As shown in , the energy delivery device 26 includes a combination of (multiple) irrigation ports 30 at or near the edge of at least one electrode 28 and (multiple) irrigation ports 30 in the electrode carrying structure 58, and a delivery sheath 60 and / or secondary device for delivering the impedance-modifying fluid 24. Further, other embodiments and combinations not shown herein are also contemplated for delivering the impedance-modifying fluid 24 to the treatment site.

[0065] Reference now Fig.11, shows a portion of an energy delivery device 26 that uses pulsed field ablation energy to ablate tissue 12 and delivers a first impedance modifying fluid 24 and a second impedance modifying fluid 24'. As discussed above, the hypotonic impedance modifying fluid will at least temporarily increase the impedance of the blood environment surrounding the electrode(s) to a level that reduces the current delivered through the blood 18, thereby mitigating or eliminating local heating generated by high current densities, and helping to direct the current toward and into the target tissue 12. However, the medical system 38 may include at least a first fluid reservoir 52 and a second fluid reservoir 52' ​​(which may optionally be in fluid communication with a second pump 54'), each of which contains a different impedance modifying fluid (24 and 24', respectively). In Fig.12 An exemplary medical system 38 for delivering a first impedance modifying fluid 24 and a second impedance modifying fluid 24' is shown in FIG. Fig.12 Medical system38 and Figure 3 The medical system 38 is similar, but includes a first fluid reservoir 52 and a second fluid reservoir 52'.

[0066] In one embodiment, Fig.11The energy delivery device 26 can be used to deliver a first impedance-modifying fluid 24 (e.g., from a first fluid reservoir 52) that is a hypotonic fluid from a first one or more flush ports 30 positioned proximal to a distal tip or distal electrode 28' of the energy delivery device 26. For example, the first one or more flush ports 30 include a first plurality of flush ports 30'. The hypotonic fluid 24 helps isolate the blood 18 from non-target tissue to reduce the occurrence of bubble and heat-denatured protein formation, and also drives electrical current toward and into the target tissue 12. The energy delivery device 26 is also used to deliver a second impedance-modifying fluid 24' (e.g., from a second fluid reservoir 52') from a second one or more flush ports 30' positioned at or near the distal tip or distal electrode 28' of the energy delivery device. For example, the second one or more flush ports 30' include a second plurality of flush ports 30' that can be similar in size and configuration to the first plurality of flush ports 30. In one embodiment, the second impedance-modifying fluid 24' is a hypertonic fluid, such as a fluid with a relatively high concentration of sodium chloride (e.g., a hypertonic solution containing 2%, 3%, 5%, or 7% sodium chloride by weight), or a fluid that includes ions that act as an adjuvant to enhance the killing power of the electric field (e.g., a solution containing calcium, such as calcium gluconate or calcium chloride). Calcium). The second impedance modifying fluid 24' will at least temporarily reduce the impedance of the blood environment surrounding the (multiple) electrodes 28 to a level that increases the current delivered through the area of ​​the first impedance modifying fluid 24 as the current approaches the target tissue 12, thereby enhancing lesion formation and filling any gaps in lesion formation of non-uniform tissue. In one embodiment, the second plurality of flush ports 30" includes fewer flush ports 30" than the first plurality of flush ports 30', and / or the pore size (diameter) of each of the first plurality of flush ports 30' is larger than the pore size of each of the second plurality of flush ports 30", thereby delivering a larger amount of the hypotonic first impedance modifying fluid 24 to the treatment site 12 compared to the hypertonic second impedance modifying fluid 24'. Further, the first impedance-modifying fluid 24 and the second impedance-modifying fluid 24' can be delivered in short bursts during or between bursts or pulses of delivered pulsed field ablation energy, thereby maintaining a certain amount of each impedance-modifying fluid 24 and 24' at a desired position (e.g., thereby maintaining the hypotonic first impedance-modifying fluid 24 at a position farther from the target tissue 12 than the hypertonic second impedance-modifying fluid 24').Alternatively, the first impedance modifying fluid 24 and the second impedance modifying fluid 24' may be delivered from the same (multiple) flushing ports 30, and the control unit 40 (e.g., the processing circuit system 48) may be configured to automatically or semi-automatically or accept user input to modify the relative concentrations of the impedance modifying fluids 24, 24' to have a greater degree of control over the depth, even with a limited set of ablation parameter selections. In one non-limiting example, the impedance modifying fluid mixture may be modified from a 20% hypertonic fluid / 80% hypotonic fluid solution (which may result in the creation of shallower lesions) to 100% hypotonic fluid (which may result in the creation of deeper lesions).

[0067] Additionally, Fig.11 The energy delivery device 26 can be used to deliver only hypertonic fluid from one or more flush ports 30, rather than only hypotonic fluid or both hypertonic and hypotonic fluids. The hypertonic fluid 24 helps the electric field spread in complex anatomical structures, thereby minimizing the effects of tissue contact. The hypertonic fluid also expands the effective surface area of ​​each electrode 28 and displaces blood from the area where the electric field is located around each electrode 28.

[0068] Reference now Figure 13-Figure 15 , shows focal delivery of bipolar pulsed field ablation energy, where Fig.14 Also shown is the delivery impedance modifying fluid 24. Fig.13 and Fig.14 In both, energy is delivered from a focal medical device, such as an energy delivery device 26 configured to deliver pulsed field ablation energy 10. In one embodiment, the energy delivery device 26 has an elongated body 62 having a distal portion 64, a proximal portion opposite the distal portion, and an energy delivery electrode 28 at the distal portion 64 (e.g., at the distal end of the elongated body 62). An energy return electrode 44 is also used, having a larger surface area than the energy delivery electrode 28 of the energy delivery device 26. The energy delivery electrode 28 provides a first (e.g., positive) polarity, while the energy return electrode 44 provides a second (e.g., negative) polarity, thereby causing the pulsed field ablation energy 10 delivered from the energy delivery electrode 28 to the target tissue 12 to flow to the energy return electrode 44. The energy return electrode 44 can be one or more energy return electrodes 44 on the secondary device 42 (e.g., such as Fig.13 and Fig.14 ) and / or one or more energy return electrodes 44 on the energy delivery device 26 (e.g., as shown in Figure 16-18). In one embodiment, the energy return electrode 44 is on the sheath. In another embodiment, the energy return electrode is on an in-dwelling device, which can reduce skeletal muscle stimulation depending on the pulse parameters and reduce the subsequent need for paralytic agents and / or reduce the risk of injury to the patient and / or user caused by unintended muscle stimulation. In another embodiment, the energy return electrode is a grounding patch applied to the patient's skin. However, any combination of energy return electrodes 44 may be used.

[0069] In another embodiment, if Fig.15 As shown in , the secondary device 42 can be positioned within the pericardial space to act as a ground plane for delivering pulsed field ablation energy from the energy delivery device 26 positioned within the heart chamber. Thus, the energy return electrode 44 can be segmented, or the secondary device 42 can include multiple energy return electrodes 44, whereby the user can select / activate multiple segments of the energy return electrode 44 or multiple energy return electrodes 44 to obtain a relatively larger surface area compared to the energy return electrode 28, or the user can select / activate fewer segments of the energy return electrode 44 or fewer energy return electrodes 44 to obtain a smaller surface area to act as an opposing electrode in an endocardial to epicardial ablation vector arrangement. When the effective surface area of ​​the (multiple) energy delivery electrode 28 is similar or identical to that of the (multiple) energy return electrode 44, the lesion 36 formed in the tissue can be formed from both the endocardium and the epicardium, thereby converging in the middle myocardium in the form of a continuous transmural lesion. When a relatively larger effective surface area of ​​the energy return electrode 44 is selected / activated, the lesion 36 will extend from the endocardium to a certain depth within the mid-myocardium, but minimal lesion formation may occur from the epicardial direction (e.g., as Fig.15 Additionally, it may be advantageous to infuse the pericardial space adjacent to the energy return electrode(s) 44 with a hypertonic solution, such as a hypertonic saline solution, to create a larger effective surface area for overall impedance reduction.

[0070] like Fig.13 and Fig.14 As shown in , delivering an impedance-modifying fluid 24 immediately prior to and / or during delivery of pulsed field ablation energy 10 enhances lesion size and depth, even during focal delivery of bipolar ablation energy using an energy return electrode. In one embodiment, the energy delivery device 26 includes one or more irrigation ports 30 proximal to the energy delivery electrode 28. Fig.14 As shown in , delivery of a hypotonic impedance modifying fluid 24 from the flush port(s) 30 will direct the current 10 away from the area of ​​increased impedance and toward and through the target tissue 12. Thus, compared to a lesion 34 created without the use of an impedance modifying fluid 24 (e.g., Fig.13), delivering the impedance-modifying fluid 24 immediately prior to and / or during the delivery of the pulsed field ablation energy 10 creates a deeper lesion 36 (e.g., as shown in Fig.14 ).

[0071] Reference now Figure 16-18 , shows an embodiment of an energy delivery device 26 that includes at least one energy return electrode 44 and at least one distance-keeping element 66. As mentioned above, the at least one energy return electrode 44 may include one or more energy return electrodes 44 on the energy delivery device 26. Figure 16-18 In the embodiment shown in FIG. 1 , the energy delivery device 26 includes an elongated body 62 having an energy delivery electrode 28 at a distal portion 64 and a plurality of energy return electrodes 44 along the elongated body 62 proximal to the energy delivery electrode 28. Fig.16 As shown in FIG. 1 , the energy delivery electrode 28 may be a distal tip electrode 28′, but it will be understood that the energy delivery electrode 28 may additionally or alternatively be an electrode positioned proximal to the distal tip of the elongated body 62. The energy delivery device 26 optionally also includes one or more flushing ports 30 for delivering the impedance modifying fluid 24. The pulsed field ablation energy 10 delivered from the energy delivery electrode 28 to the target tissue 12 may flow to a plurality of energy return electrodes 44, such as Fig.13 and Fig.14 As shown in . Further, each energy return electrode 44 can be in electrical communication with the control unit 40 (during automatic or semi-automatic system operation) and can be individually controlled by the control unit 40 and / or the user (during manual system operation). In one embodiment, the energy delivery electrode 28 and / or additional (multiple) electrodes 67 (such as mapping electrodes) at the distal portion 64 of the slender body 62 are used to record electrograms (EGMs) from the target tissue 12 and transmit the data to the control unit 40. Additionally or alternatively, the control unit 40 and / or the user selectively activates or disables individual energy return electrodes 44 based on their positions relative to the (multiple) energy delivery electrodes 28, so as to achieve the desired energy delivery vector pathway, potentially avoid non-target structures (such as nerves or skeletal muscles), and also create a desired ablation pattern or lesion depth. For example, the control unit 40 may compare the recorded EGM with a threshold EGM value and selectively activate or disable a single energy return electrode 44 based on the comparison. The control unit 40 may also be configured to warn the user and / or prevent the delivery of pulsed field ablation energy if the control unit 40 determines that too few energy return electrodes 44 are activated. The control unit 40 may also collect position navigation information via an electromagnetic or potentiometric navigation system that will define the relative physical locations of the energy delivery electrode(s) 28 and the energy return electrode(s) 44 in space.

[0072] exist Figure 16-18 In the embodiment shown in , the energy delivery device 26 further includes at least one distance-keeping element 66. Each distance-keeping element 66 is made of a non-conductive material, such as plastic, silicone, rubber, etc. Further, each distance-keeping element 66 maintains a distance d between the (multiple) energy return electrodes 44 and the non-target tissue 12', and during the energy delivery procedure, the (multiple) energy return electrodes 44 may contact the non-target tissue 12'. In other words, the outer diameter of each distance-keeping element 66 is larger than the outer diameter of the energy return electrode 44. Fig.16 , at least one distance-keeping element 66 includes a plurality of fins 68 that spirally surround at least a portion of the elongated body 62. However, the distance-keeping element 66 may have other configurations, including but not limited to Fig.17 and Fig.18 Those configurations shown in .

[0073] refer to Fig.17 , each distance-keeping element 66 includes one or more rings 70. In one embodiment, each distance-keeping element 66 includes a plurality of rings 70 having various outer diameters, thereby making each distance-keeping element 66 tapered in at least one of the proximal-to-distal direction and the distal-to-proximal direction. Additionally or alternatively, each distance-keeping element 66 includes a single ring 70 having a diameter greater than the outer diameter of the elongated body 62 near the distance-keeping element 66. Additionally or alternatively, with reference to Fig.18 , each distance-keeping element 66 includes one or more curved or arcuate splines 72 extending in a direction parallel to the elongated body 62. However, it will be understood that other configurations may be used, provided that each distance-keeping element 66 is sized and configured to maintain a distance d between the (multiple) energy return electrodes 44 and the non-target tissue 12'. Further, each distance-keeping element 66 can be convertible between a delivery configuration and an extended configuration. In the delivery configuration, the distance-keeping element 66 is positioned proximate to or against the elongated body 62 to facilitate navigation through the patient's vasculature and reduce the possibility of patient injury. Figure 16-18 An exemplary extended configuration is shown in FIG. The distance-keeping element 66 may be mechanically connected to one or more actuating elements (e.g., one or more rods, pullwires, knobs, etc.) that enable a user to switch the distance-keeping element 66 between the delivery configuration and the extended configuration. Additionally or alternatively, the distance-keeping element 66 may be constructed of a flexible or highly flexible material that is biased toward the extended configuration but allows the distance-keeping element 66 to be easily compressed against the elongated body 62 (delivery configuration) during navigation to the treatment site without causing damage to surrounding tissue.

[0074] In a first step of an exemplary method for delivering pulsed field ablation energy and an impedance-modifying fluid 24, at least one energy delivery electrode 28 of an energy delivery device 26 is positioned within the patient's body and proximate to a region of target tissue 12. In an optional second step, at least one energy return electrode 44 is positioned at a desired distance from the at least one energy delivery electrode 28. In one embodiment, the at least one energy return electrode 44 is on or coupled to the energy delivery device 26 (e.g., such as Figure 16-18 ). Additionally or alternatively, at least one energy return electrode 44 is positioned on a secondary device 42 (such as a device that remains in the body), and / or adhered to an external surface of the patient's body. In an optional third step, EGMs from the target tissue 12 are recorded by one or more mapping electrodes on the energy delivery electrode 28 and / or the energy delivery device 26 and / or the secondary mapping device, coupled to the energy delivery device 26 and / or the secondary mapping device, or otherwise carried on the energy delivery device 26 and / or the secondary mapping device. The EGM data is then transmitted from the energy delivery device 26 and / or the secondary mapping device 42 to the control unit 40, where the processing circuit system 48 can use the EGM data to determine whether to: selectively activate or disable one or more of the at least one energy return electrode 44 and / or display an alert or suggestion to the user to manually activate or disable one or more of the at least one energy return electrode 44 (for example, via a user input device 50 that communicates with the control unit 40 or is included in the control unit 40). Additionally, EGM may continue to be recorded and activation / deactivation of at least one energy return electrode 44 modified during and / or after delivery of pulsed field ablation energy 10 .

[0075] In a first exemplary fourth step, the processing circuit system 48 instructs the pump 54 to deliver a bolus or volume of at least one impedance-modifying fluid 24 from the energy delivery device 26 at a location proximate to the target tissue / treatment site 12. In one embodiment, the processing circuit system 48 instructs the pump 54 to deliver a volume of approximately 4 mL of hypotonic fluid over a period of approximately two seconds. In another embodiment, the processing circuit system instructs the pump 54 to deliver a first volume of hypotonic fluid 24 and a second volume of hypertonic fluid 24' (e.g., Fig.11). Optionally, the impedance-modifying fluid 24 may be expelled from the treatment site 12 during and after delivery of the impedance-modifying fluid and after delivery of pulsed field ablation energy. The energy return electrode(s) 44 provide a low impedance, large conductive region that generally does not achieve a sufficiently high electric field strength around it to ablate adjacent tissue. Delivery of a second impedance-modifying fluid 24' having a higher conductivity to the region around the energy return electrode(s) 44 increases the effective conductivity of the energy return path and reduces the likelihood that the local field gradient reaches the ablation threshold field gradient, particularly at points where the metal energy return electrode(s) 44 contact non-target tissue. In such cases, it may be advantageous to deliver a hypertonic solution (such as a second impedance-modifying fluid 24', e.g., a 2% saline solution) around the return path electrode.

[0076] In a first exemplary fifth step, the processing circuit system 48 instructs the energy generator 46 to deliver pulsed field ablation energy (current) 10 from the at least one energy delivery electrode 28 to the target tissue 12 after a duration of about two seconds has occurred since delivery of the impedance-modifying fluid 24. That is, immediately prior to or about two seconds prior to at least the first pulse of the delivery current 10 (i.e., the first pulse of the pulsed field ablation energy 10), the impedance-modifying fluid 24 is delivered to the treatment site 12. In one embodiment, between about 1 mL (±0.2 mL) and about 6 mL (±0.2 mL) of the fluid is delivered to the treatment site at a delivery rate of about 1 mL / sec to about 2 mL / sec.

[0077] In a second exemplary fourth step, and in addition to or in lieu of the first exemplary fourth step, the processing circuit system 48 instructs the pump 54 and the energy generator 46 to simultaneously deliver the impedance-modifying fluid 24 and the pulsed field ablation energy 10, respectively, so that the impedance-modifying fluid 24 and the current 10 are delivered to the treatment site 12 at the same time. The impedance-modifying fluid 24 is delivered as a small volume and / or is delivered for a short duration. For example, the impedance-modifying fluid 24 is delivered at a rate of about 1 mL / min to about 2 mL / sec. Optionally, one or more additional volumes of the impedance-modifying fluid 24 are delivered to the treatment site 12 during the delivery of the pulsed field ablation energy. Optionally, the impedance-modifying fluid 24 may be discharged from the treatment site 12 during or after the delivery of the pulsed field ablation energy.

[0078] Although these steps include delivering an impedance-modifying fluid 24, it will be understood that the pulsed field ablation energy 10 may be delivered to the treatment site prior to delivering the impedance-modifying fluid 24 or after the volume of the impedance-modifying fluid 24 has dissipated from the treatment site 12. This may allow the user to have greater control over creating lesions of various depths and sizes and / or modifying the size or depth of previously created lesions. Additionally, one or both of a hypotonic and a hypertonic fluid may be used. If a mixture of hypotonic and hypertonic fluids is used, the relative concentrations of each fluid may be adjusted prior to and / or during the delivery of the pulsed field ablation energy to create the desired lesion size and / or depth.

[0079] In a sixth step, the energy delivery device 26 and any secondary devices are removed from the patient.

[0080] In one embodiment, a system for ablating tissue at a treatment site includes: an energy delivery device; and a control unit including: an impedance-modifying fluid source in fluid communication with the energy delivery device; an energy generator in electrical communication with the energy delivery device and configured to transmit energy to the energy delivery device, and the energy delivery device is configured to deliver energy to the treatment site; and a processing circuit system configured to control the delivery of the impedance-modifying fluid from the energy delivery device to the treatment site.

[0081] In one aspect of this embodiment, the processing circuit system is configured to control the delivery of an impedance modifying fluid from the energy delivery device, thereby causing the energy delivery device to deliver the impedance modifying fluid to the treatment site before commencing delivery of energy from the energy delivery device to the tissue site. In one aspect of this embodiment, the energy delivery device delivers the impedance modifying fluid to the treatment site at a flow rate between about 1 mL / min and about 120 mL / min (about 2 mL / sec). In one aspect of this embodiment, the energy delivery device delivers the impedance modifying fluid to the treatment site about two seconds before commencing delivery of energy from the energy delivery device to the tissue site.

[0082] In one aspect of this embodiment, the processing circuitry is configured to control delivery of an impedance modifying fluid from the energy delivery device, thereby causing the energy delivery device to deliver the impedance modifying fluid to the treatment site simultaneously with initiating delivery of energy from the energy delivery device to the tissue site.

[0083] In one aspect of this embodiment, the impedance modifying fluid is a hypotonic fluid. In one aspect of this embodiment, the hypotonic fluid is a physiological saline solution comprising less than 0.9% by weight sodium chloride.

[0084] In one embodiment, the hypotonic fluid comprises at least one of glucose, dextrose, calcium, calcium gluconate, and calcium chloride.

[0085] In one aspect of this embodiment, the impedance modifying fluid is a hypertonic fluid.

[0086] In one aspect of this embodiment, the energy delivery device comprises at least one flushing port in fluid communication with a source of impedance-modifying fluid. In one aspect of this embodiment, the energy delivery device further comprises at least one energy delivery electrode, the at least one flushing port satisfying at least one of the following: in the at least one electrode, and in close proximity to the at least one electrode.

[0087] In one aspect of this embodiment, each of the at least one energy delivery electrode has a first edge and a second edge proximal to the first end, and at least one irrigation port in the electrode is proximate to at least one of the first edge and the second edge.

[0088] In one aspect of this embodiment, the energy delivery device further comprises an electrode carrying structure to which the at least one electrode is coupled, and wherein the at least one irrigation port is in the electrode carrying structure.

[0089] In one aspect of this embodiment, the impedance modifying fluid source is a first impedance modifying fluid source, the control unit further comprises a second impedance modifying fluid source in fluid communication with the energy delivery device. In one aspect of this embodiment, the first impedance modifying fluid is a hypotonic fluid, and the second impedance modifying fluid is a hypertonic fluid, the processing circuit system is configured to control delivery of the first impedance modifying fluid and the second impedance modifying fluid from the energy delivery device, thereby causing the energy delivery device to simultaneously deliver the first impedance modifying fluid to a first portion of the treatment site and the second impedance modifying fluid to a second portion of the treatment site.

[0090] In one aspect of this embodiment, the first impedance-modifying fluid is a hypotonic fluid and the second impedance-modifying fluid is a hypertonic fluid, the energy delivery device is configured to deliver the first impedance-modifying fluid and the second impedance-modifying fluid together as a mixture, and the processing circuit system is configured to modify the amount of at least one of the first impedance-modifying fluid and the second impedance-modifying fluid to change the mixture at least one of before or during delivery of energy from the energy delivery device.

[0091] In one embodiment, a method for ablating tissue includes delivering an impedance modifying fluid to a treatment site and delivering pulsed field ablation energy to the treatment site.

[0092] In one aspect of this embodiment, the treatment site includes a region of target tissue and blood in contact with the region of target tissue, pulsed field ablation energy is delivered to the region of target tissue and an impedance modifying fluid is delivered to the blood.

[0093] In an aspect of this embodiment, an impedance modifying fluid is delivered to the blood immediately prior to delivering pulsed field ablation energy to the region of target tissue.

[0094] In one aspect of this embodiment, an impedance modifying fluid is delivered to the blood simultaneously with delivering pulsed field ablation energy to a region of target tissue.

[0095] In one aspect of this embodiment, the treatment site includes a region of epicardial tissue and a pericardial space in contact with the region of epicardial tissue, pulsed field ablation energy is delivered to the region of epicardial tissue and an impedance modifying fluid is delivered to the pericardial space.

[0096] In one embodiment, a tissue ablation device includes: an elongated body having a distal portion and a proximal portion opposite the distal portion, the distal portion including a distal end; an energy delivery electrode located at the distal portion of the elongated body; an energy return electrode on the elongated body, proximal to the energy delivery electrode; and a distance maintaining element on the elongated body, close to the energy return electrode.

[0097] In one aspect of this embodiment, the distance maintaining element has a first outer diameter and the energy return electrode has a second outer diameter that is smaller than the first outer diameter.

[0098] In one aspect of this embodiment, the distance-keeping element is composed of a non-conductive material. In one aspect of this embodiment, the distance-keeping element is at least one of a fin, a ring, and a spline.

[0099] In an aspect of this embodiment, the distance keeping element is convertible between a delivery configuration and an extended configuration.

[0100] It should be understood that the various aspects disclosed herein may be combined in combinations different from those specifically presented in the specification and drawings. It should also be understood that, according to examples, certain actions or events of any of the processes or methods described herein may be performed in different orders, and certain actions or events of any of the processes or methods described herein may be added, merged, or omitted altogether (e.g., not all described actions or events are necessary for performing the technology). In addition, although certain aspects of the present disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the technology of the present disclosure may be performed by a combination of units or modules associated with, for example, a medical device.

[0101] In one or more examples, the described techniques may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or codes on a computer-readable medium and executed by a hardware-based processing unit. A computer-readable medium may include a non-transient computer-readable storage medium, which corresponds to a tangible medium, such as a data storage medium (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and can be accessed by a computer).

[0102] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuit systems. Accordingly, the term "processor" as used herein may refer to any of the above structures or any other physical structure suitable for implementing the described techniques. In addition, these techniques may be fully implemented in one or more circuits or logic elements.

[0103] It will be appreciated by those skilled in the art that the present invention is not limited to the contents specifically shown and described herein above. In addition, unless otherwise mentioned above, it should be noted that all drawings are not to scale. Various modifications and variations are possible under the inspiration of the above teachings without departing from the scope and spirit of the present invention, which is limited only by the appended claims.

Claims

1. A system for ablating tissue at a treatment site, the system comprising: an energy delivery device comprising one or more energy delivery electrodes; as well as A control unit, the control unit comprising: a source of impedance modifying fluid in fluid communication with the energy delivery device; an energy generator in electrical communication with the one or more energy delivery electrodes of the energy delivery device, the energy generator being configured to transmit pulsed field ablation energy to the one or more energy delivery electrodes of the energy delivery device, and the one or more energy delivery electrodes of the energy delivery device being configured to deliver the pulsed field ablation energy to the treatment site; and processing circuitry configured to: controlling delivery of the impedance modifying fluid from the energy delivery device to the treatment site, to change the impedance of the blood tissue environment; and If the impedance of the blood-tissue environment has changed sufficiently by a desired amount to enhance lesion formation and limit embolism formation, the energy generator is commanded to deliver the pulsed field ablation energy.

2. The system according to claim 1, characterized in that The processing circuitry is configured to control delivery of the impedance modifying fluid from the energy delivery device, thereby causing the energy delivery device to deliver the impedance modifying fluid to the treatment site prior to initiating delivery of energy from the energy delivery device to the treatment site.

3. The system according to claim 1, characterized in that The impedance modifying fluid is at least one of a hypotonic fluid and a hypertonic fluid.

4. The system according to claim 3, characterized in that The impedance modifying fluid is a hypotonic fluid, which is a physiological saline solution comprising less than 0.9% by weight of sodium chloride.

5. The system according to claim 3, characterized in that The impedance modifying fluid is a hypotonic fluid comprising at least one of glucose, dextrose, calcium, calcium gluconate, and calcium chloride.

6. The system according to any one of claims 1 to 5, characterized in that: The energy delivery device includes at least one flush port in fluid communication with the impedance modifying fluid source.

7. The system according to claim 6, characterized in that The at least one irrigation port satisfies at least one of the following: within the one or more energy delivery electrodes, and in close proximity to the one or more energy delivery electrodes.

8. The system according to claim 7, characterized in that Each of the one or more energy delivery electrodes has a first edge and a second edge opposite the first edge, and the at least one irrigation port in the energy delivery electrode is proximate to at least one of the first edge and the second edge.

9. The system according to claim 7, characterized in that The energy delivery device further comprises an electrode carrying structure to which the one or more energy delivery electrodes are coupled, the at least one irrigation port being in the electrode carrying structure.

10. The system according to any one of claims 1 to 5, characterized in that: The impedance modifying fluid source is a first impedance modifying fluid source, and the control unit further comprises a second impedance modifying fluid source in fluid communication with the energy delivery device.

11. The system according to claim 10, characterized in that The first impedance-modifying fluid is a hypotonic fluid and the second impedance-modifying fluid is a hypertonic fluid, the processing circuitry being configured to control delivery of the first impedance-modifying fluid and the second impedance-modifying fluid from the energy delivery device, thereby satisfying at least one of the following: the energy delivery device simultaneously delivering the first impedance modifying fluid to a first portion of the treatment site and the second impedance modifying fluid to a second portion of the treatment site; as well as The energy delivery device delivers the first impedance modifying fluid and the second impedance modifying fluid together as a mixture, and the processing circuit system is configured to modify the amount of at least one of the first impedance modifying fluid and the second impedance modifying fluid to change the mixture at least one of before and during energy delivery from the energy delivery device.

12. The system according to any one of claims 1 to 5, characterized in that: The energy delivery device comprises: an elongated body having a distal portion and a proximal portion opposite the distal portion, the distal portion including a distal end; an energy delivery electrode located at the distal portion of the elongated body; an energy return electrode on the elongated body proximal to the energy delivery electrode, the energy return electrode having a first outer diameter; and A distance-keeping element is on the elongated body, adjacent to the energy return electrode, the distance-keeping element being made of a non-conductive material and having a second outer diameter greater than the first outer diameter.

13. The system according to claim 12, characterized in that The distance keeping element is convertible between a delivery configuration and an extended configuration, and when the distance keeping element is in the extended configuration, the distance keeping element has the second outer diameter.

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