Dynamic ablation and sensing of contact based on segmented electrodes

Abstract

The present invention is entitled "Dynamic Ablation and Sensing Based on Contact of Segmented Electrodes." A system includes an expandable distal tip of a catheter and a processor. The expandable distal tip has a plurality of electrodes configured to be placed in contact with tissue in an organ and to apply ablative power to the tissue. The processor is configured to determine whether physical contact between the electrodes and the tissue meets a predefined contact quality during application of the ablation power, and if the physical contact between the electrodes and the tissue does not meet the predefined contact quality, reuse the electrodes for electrophysiological (EP) sensing.

Description

Technical Field

[0001] The present invention relates generally to medical probes and, in particular, to cardiac radiofrequency (RF) ablation and electrophysiological (EP) sensing multi-electrode catheters. Background Art

[0002] Techniques for performing temperature-monitored ablation of body tissue using medical probes have been previously proposed in the patent literature. For example, U.S. Patent 6,053,912 describes systems and associated methods for ablating body tissue that employ electrodes for contacting tissue to form a tissue-electrode interface. The electrodes are adapted to be connected to an ablation energy source to conduct ablation energy so that it is transmitted by the electrodes into the tissue at the tissue-electrode interface. The systems and methods also include an element for cooling the electrodes. The systems and methods maintain a tissue temperature sensing element in a carrier that is in thermally conductive contact with tissue below the tissue-electrode interface. The systems and methods include a controller coupled to the tissue temperature sensing element to control the supply of ablation energy or the rate of electrode cooling or both based at least in part on a temperature sensed by the temperature sensing element.

[0003] As another example, U.S. Patent No. 5,496,312 describes a control device that responds to the impedance and temperature between the active electrode and the return electrode of an electrosurgical generator during tissue desiccation. Tissue contacts are individually and independently supplied with high-frequency power to electrosurgically act on tissue. A control method responds to tissue impedance by individually and independently supplying high-frequency power to the contacts and monitoring, adjusting, and controlling the impedance between the contacts and the return electrode. The method sets the generator power applied by each contact and transmits a temperature value of each contact to a sensor to adjust the contact power. Summary of the Invention

[0004] The present invention provides a system comprising an expandable distal tip of a catheter and a processor. The expandable distal tip has a plurality of electrodes configured to be placed in contact with tissue in an organ and to apply ablative power to the tissue. The processor is configured to determine whether physical contact between the electrodes and the tissue meets a predefined contact quality during application of the ablative power, and if physical contact between one of the electrodes and the tissue does not meet the predefined contact quality, reuse the electrodes for electrophysiological (EP) sensing.

[0005] In some exemplary embodiments, the ablation power includes at least one of radio frequency (RF) power output by a RF generator and irreversible electroporation (IRE) pulses output by an IRE pulse generator.

[0006] In some exemplary embodiments, the system further includes a switching component configured to switch the electrode between the generator of the ablation power and an EP sensing system, wherein the processor is configured to control the switching component to (i) initially connect the electrode to the generator and (ii) subsequently connect the electrode to the EP sensing system so as to reuse the electrode for EP sensing.

[0007] In an exemplary embodiment, each of the electrodes comprises a plurality of electrode segments, wherein the switching assembly and the processor are configured to individually switch any one of the electrode segments between the generator and the EP sensing system.

[0008] In another exemplary embodiment, the system further comprises a switching assembly configured to initially connect each of the electrodes in parallel to the generator of the ablation power and the EP sensing system, wherein the processor is configured to control the switching assembly to subsequently disconnect the electrode from the generator so as to reuse the electrode for EP sensing.

[0009] In yet another exemplary embodiment, each of the electrodes comprises a plurality of electrode segments, wherein the switching assembly and the processor are configured to individually disconnect any one of the electrode segments from the generator.

[0010] In some exemplary embodiments, the processor is configured to determine whether the physical contact of the electrodes meets the predefined contact quality by evaluating a preset temperature criterion. In other exemplary embodiments, the processor is configured to evaluate the preset temperature criterion by evaluating the measured temperature of the electrodes relative to a preset threshold temperature.

[0011] In another exemplary embodiment, the processor is configured to determine whether the physical contact of the electrodes meets the predefined contact quality by evaluating a preset impedance criterion. In another exemplary embodiment, the processor is configured to evaluate the impedance criterion by assessing whether the frequency dependence of the impedance indicates that the electrode is in contact with blood or in contact with tissue.

[0012] According to an exemplary embodiment of the present invention, a method is further provided, comprising placing an expandable distal end of a catheter having a plurality of electrodes in contact with tissue of an organ. Applying ablation power to the plurality of electrodes. During the application of the ablation power, determining whether physical contact between the electrodes and the tissue satisfies a predefined contact quality. If the physical contact between an electrode of the electrodes and the tissue does not satisfy the predefined contact quality, reusing the electrode for electrophysiological (EP) sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will be more fully understood through the following detailed description of embodiments of the present invention in conjunction with the accompanying drawings, in which:

[0014] Figure 1 is a schematic pictorial illustration of a catheter-based position tracking and balloon ablation system according to an exemplary embodiment of the present invention;

[0015] Figure 2 is deployed in the region of the pulmonary vein (PV) and its ostium according to an exemplary embodiment of the present invention Figure 1 A schematic pictorial side view of the distal end of a balloon catheter;

[0016] Figure 3 is a schematic description of an exemplary embodiment according to the present invention Figure 1 a block diagram of the functionality of a processor-controlled switching box; and

[0017] Figure 4 is a schematic illustration of an exemplary embodiment of the present invention for use interchangeably with Figure 2 Flowchart of a method of using a segmented electrode of a balloon catheter for sensing and ablation. DETAILED DESCRIPTION

[0018] Overview

[0019] In order to perform efficient ablation using a medical probe (such as an intracardiac radiofrequency (RF) multi-electrode catheter and / or an irreversible electroporation (IRE) multi-electrode catheter), it is important that the ablation electrodes disposed on the catheter make good physical contact with the tissue being ablated. For example, when a balloon catheter with multiple ablation electrodes is used to ablate tissue in an organ, such as the ostium of a pulmonary vein (PV), typically all of the catheter electrodes are positioned to contact the PV. However, some of the electrodes may not be in sufficient physical contact to achieve effective and safe ablation.

[0020] Similarly, with other multi-electrode catheters, such as the lasso catheter (manufactured by Biosense Webster, Irvine, California) or basket catheters, these multi-electrode catheters may also have only a portion of their electrodes in sufficient contact with tissue to perform ablation.

[0021] For these electrodes, instead of ablating tissue, the applied RF power may cause undesirable effects, such as clot formation. In the case of IRE, incomplete PV isolation may occur, but there are no known undesirable effects.

[0022] In the context of this patent application, the term "applying ablation power" encompasses both applying RF power and applying IRE pulses. Typically, ablation power includes RF power output by a radiofrequency (RF) generator or irreversible electroporation (IRE) pulses output by an IRE pulse generator. However, a single generator can be configured to output RF power and IRE pulses interchangeably.

[0023] The exemplary embodiments of the present invention described below provide techniques for applying ablation and electrophysiological (EP) sensing in a spatially selectable manner. In some exemplary embodiments, an expandable multi-electrode catheter (e.g., an inflatable balloon catheter) is provided, which includes electrodes divided into segments (i.e., divided into electrode segments). A processor-controlled switching box (also referred to as a switching assembly) is also provided. During the application of ablation power by the electrode segments, the processor can switch to reuse the electrode segments as sensors by controlling the switching box, depending on whether one of the electrode segments of the electrode segments of the multi-electrode catheter contacts tissue and the degree of contact of the one electrode segment with the tissue. In another exemplary embodiment, the processor controlling the switching box can switch the electrode segments between operating as an ablation electrode and operating as a sensing electrode, which is applied, for example, to acquire intracardiac electrogram signals (i.e., for electrophysiological (EP) sensing).

[0024] In some exemplary embodiments, in the manner of an example of a multi-electrode catheter, a balloon catheter is provided with ten electrodes placed on the membrane of the balloon. Each of the ten electrodes is divided into four segments, wherein one or more temperature sensors (such as thermocouples) are located on each electrode segment. Initially, when the catheter is positioned to contact the port, the switching box connects all segments of each electrode as ablation electrodes, and RF ablation power is supplied to the electrodes. During the application of ablation power to the electrode segments, one or more temperature sensors sense the rising temperature of the electrode segments in real time.

[0025] The temperature of each electrode segment is monitored by a processor that receives temperature readings sensed by one or more temperature sensors. The processor uses a preset temperature criterion (such as the relationship of the temperature reading relative to a preset threshold temperature) to determine the adequacy of the contact (i.e., determine whether the physical contact between any one of the electrodes and the tissue meets a predefined contact quality with the tissue). For example, if the temperature reading of the electrode segment is above a preset threshold temperature (e.g., a threshold determined by a previous experiment), the processor determines that the contact between the electrode segment and the tissue is good, i.e., the predefined contact quality criterion is met, and determines that the tissue is being ablated. In this case, the switch box continues to connect the electrode segment to the ablation power source.

[0026] On the other hand, if the temperature of the electrode segment does not rise above the threshold temperature, the processor determines that the level of contact of the electrode segment with the tissue is insufficient (meaning that the ablation energy is mainly heating the blood). In this case, the processor controls the switch box to switch the electrode segment from receiving ablation power to acting as a sensing electrode.

[0027] In one exemplary embodiment, it is sufficient that one of the one or more temperature sensors measures a temperature below or equal to a threshold temperature to switch an electrode segment to a sensing electrode. In another exemplary embodiment, the processor compares the average temperature sensed by the one or more temperature sensors with the threshold temperature and controls the switching box based on the average electrode segment temperature.

[0028] In an alternative exemplary embodiment, the switching assembly is configured to initially connect each of the electrode segments in parallel to a generator of ablation power and the EP sensing system. Upon determining that the level of contact of a given electrode segment with tissue is insufficient, the processor is configured to control the switching assembly to disconnect the electrode segment from the generator.

[0029] In some exemplary embodiments, the ablation system is additionally or alternatively configured to measure the impedance between each electrode segment and the tissue. The system's processor analyzes characteristics of the measured impedance, such as the different frequency dependencies of the impedance of blood and tissue, and uses the results of this analysis to provide an independent assessment for each electrode segment as to whether the electrode segment is in direct electrical contact with the cardiac tissue (i.e., touching) or not in contact (e.g., the electrode segment is mostly immersed in blood).

[0030] When using impedance measurement alone, the switch box initially connects all electrode segments in all electrodes as sensing electrodes. The catheter is positioned in contact with tissue (such as tissue at the ostium of a PV) and the impedance is measured. Each electrode has a frequency-dependent impedance that indicates tissue connected to the ablation power source by the processor using the switch box. Electrode segments with frequency-dependent impedances indicative of blood are switched to sensing electrodes by the processor.

[0031] In some exemplary embodiments, just before applying RF power, the aforementioned impedance measurement-based indication of contact with tissue can be used, for example, to reposition the multi-electrode catheter inside the lumen to improve contact at electrode segments determined to be mostly in contact with blood.

[0032] Techniques for sensing electrode-tissue physical contact using analysis of the frequency response of tissue are described in U.S. patent application Ser. No. 15 / 991,291, filed May 29, 2018, entitled "Touch Detection by Different Frequency Response of Tissue," which is assigned to the assignee of the present patent application and the disclosure of which is incorporated herein by reference. In one exemplary embodiment, a processor may use this method to analyze acquired intracardiac signals. However, other techniques that utilize electrical measurements provided by segmented electrodes to assess the level of contact with tissue may be used.

[0033] In some exemplary embodiments, electrode segment temperature and impedance are measured and analyzed in real time (ie, during application of ablation power). Using both indicators to determine whether an electrode segment can be used for ablation or only for sensing can enhance the clinical selectivity of the disclosed technology.

[0034] Typically, the processor is programmed with software containing specific algorithms that enable the processor to perform each of the processor-related steps and functions listed above.

[0035] By providing electrode segments that can be switched based on the quality of contact with tissue, the disclosed segmented balloon ablation technology can provide safer and more effective balloon ablation treatments. This, in turn, can improve the clinical outcomes of cardiac balloon ablation treatments, such as pulmonary vein (PV) isolation for the treatment of arrhythmias.

[0036] System Description

[0037] Figure 1 is a schematic pictorial illustration of a catheter-based position tracking and balloon ablation system 20 according to an exemplary embodiment of the present invention. The system 20 includes a catheter 21 fitted with an RF ablation inflatable balloon 40 including a segmented electrode 50 (see inset 25) at the distal end 22a of the catheter's shaft 22. In the exemplary embodiment described herein, the segmented electrode 50 is used to ablate tissue at the ostium 51 of a PV in the heart 26.

[0038] The proximal end of the catheter 21 is connected to a console 24 that includes an ablation power source 45. The console 24 includes a switch box 46 (also called a switch assembly) that can switch any segment of the segmented electrode 50 between acting as an ablation electrode and acting as a sensing electrode. An ablation protocol including ablation parameters (including preset temperature and / or impedance criteria) is stored in a memory 48 of the console 24.

[0039] A physician 30 inserts the distal end 22a of the shaft 22 through the sheath 23 into the heart 26 of a patient 28 lying on a table 29. The physician 30 navigates the distal end of the shaft 22 to a target location in the heart 26 by manipulating the shaft 22 using a manipulator 32 near the proximal end of the catheter and / or by deflecting the sheath 23. During insertion of the distal end 22a, the balloon 40 is held in a collapsed configuration by the sheath 23. By containing the balloon 40 in a collapsed configuration, the sheath 23 also serves to minimize trauma to blood vessels along the way to the target location.

[0040] Once distal end 22a of shaft 22 has reached the target location, physician 30 retracts sheath 23 and inflates balloon 40 and further manipulates shaft 22 to place segmented electrodes 50 disposed over the perimeter of balloon 40 in contact with ostia 51 of the pulmonary veins.

[0041] Electrode 50 is connected by wires passing through shaft 22 to processor 41 which controls switch box 46 of interface circuit 44 located in console 24. To perform its functions, processor 41 includes ablation electrode impedance sensing module 47 and temperature sensing module 49.

[0042] The impedance sensing module 47 receives the electrical impedance signals measured between the segmented electrodes 50 and the surface electrodes 38, which in the exemplary system are considered to be attached by wires that pass through the cable 37 to the chest of the patient 28. Methods for tracking the position of the electrodes 50 using the measured impedance are implemented in various medical applications, such as in the CARTO TM The method is implemented in a system and is described in detail in U.S. Patents 7,756,576, 7,869,865, 7,848,787, and 8,456,182, the disclosures of which are incorporated herein by reference. This method is sometimes referred to as Advanced Catheter Positioning (ACL). Console 24 drives display 27, which displays the tracked position of balloon 40 inside heart 26.

[0043] As further shown in inset 25, distal end 22a includes a magnetic position sensor 39 contained within distal end 22a, just proximal to inflatable balloon 40. During navigation of distal end 22a in heart 26, console 24 receives signals from magnetic sensor 39 in response to a magnetic field from external field generator 36, for example, to measure the position of ablation balloon 40 in the heart, and optionally presents the tracked position on display 27. Magnetic field generator 36 is placed at a known location external to patient 28, for example, beneath the patient's table 29. Console 24 also includes drive circuitry 34 configured to drive magnetic field generator 36.

[0044] Position sensing methods using external magnetic fields are implemented in various medical applications, such as in the CARTO TM 6,332,089, PCT Patent Publication No. WO 96 / 05768, and U.S. Patent Application Publication Nos. 2002 / 0065455 Al, 2003 / 0120150 Al, and 2004 / 0068178 Al, the disclosures of which are incorporated herein by reference.

[0045] As noted above, console 24 includes a processor 41, typically a general purpose computer, having a suitable front end, and interface circuitry 44 for receiving signals from catheter 21 and for applying RF energy therapy to the left atrium of heart 26 via catheter 21, and for controlling other components of system 20. Processor 41 typically includes software in memory 48 of system 20 that is programmed to implement the functions described herein. The software may be downloaded to the computer in electronic form over a network, for example, or it may alternatively or additionally be provided and / or stored on a non-transitory tangible medium such as magnetic, optical, or electronic memory. Specifically, processor 41 operates as disclosed herein and includes Figure 4 , which enables the processor 41 to perform the disclosed steps, as further described below.

[0046] Dynamic ablation and sensing of contact based on segmented electrodes

[0047] Figure 2 is deployed in the area of ​​the pulmonary vein (PV) and its ostium 51 according to an exemplary embodiment of the present invention Figure 1Schematic pictorial side view of a balloon catheter. The balloon catheter is used to ablate tissue 51 to isolate the source of an arrhythmia. The balloon 40 has ten segmented electrodes 50 disposed on a membrane 71 of the balloon. RF power can be delivered from an ablation power source 45 independently to each of the four electrode segments 55 of each of the ten electrodes 50, depending on the level of physical contact each segment 55 has with the tissue during ablation.

[0048] Each of the electrode segments 55 is adapted with a temperature sensor 57 in order to monitor the temperature of the electrode segment 55 during ablation. Figure 2 A single temperature sensor 57 is shown for each electrode segment 55, but typically several temperature sensors 57 are provided on each electrode segment 55. The lowest temperature reading or the average temperature reading for each electrode segment can be used to determine the quality of the physical contact of the segment 55 with the tissue.

[0049] like Figure 2 As can be seen in FIG, electrode segment 55a is not in good contact with the tissue. Based on the temperature reading from sensor 57a being lower than or equal to the preset threshold temperature during ablation, processor 41 determines that the physical contact of electrode segment 55a is insufficient. In response, processor 41 controls switch box 46 to switch electrode segment 55a to a sensing electrode.

[0050] In an alternative exemplary embodiment, the switch box 46 initially connects all electrode segments 55 of all electrodes 50 in parallel to the ablation power source 45 and the EP sensing system. Upon determining that the level of contact with the tissue by a given electrode segment 55 is insufficient, the processor 41 controls the switch box 46 to disconnect the electrode segment from the generator and, in this manner, facilitate reuse of that electrode segment for EP sensing.

[0051] Figure 2 The pictorial side view shown in is selected by way of example, wherein other embodiments are also possible. For example, in another exemplary embodiment, cooling fluid is sprayed through irrigation holes (not shown) in the electrode 50 to cool the ablated tissue. Although Figure 2 A multi-electrode balloon catheter is described, but the principles of the disclosed technology are applicable to any catheter having a distal end fitted with multiple electrodes, such as the aforementioned lasso and basket catheters.

[0052] Figure 3 is a schematic description of an exemplary embodiment according to the present invention Figure 1FIG4 is a block diagram of the functionality of a processor-controlled switch box 46. As shown, in response to commands from processor 41, switch box 46 connects the electrode segments to ablation power or connects the electrode segments as sensing electrodes. For example, switch box 46 connects the electrode segments to the position sensing subsystem of system 20 to provide a signal position to be used with the aforementioned ACL position tracking method.

[0053] Highly simplified Figure 3 Therefore, system components that do not directly contribute to the clarity of the presentation have been omitted.

[0054] Figure 4 is a schematic illustration of an exemplary embodiment of the present invention for use interchangeably with Figure 2 FIG2 is a flow chart of a method for using a segmented electrode of a balloon catheter for sensing and ablation. According to the exemplary embodiment shown, the algorithm implements a process that begins at a balloon catheter positioning step 80 when the physician 30 positions the balloon catheter at a target location within the patient's lumen, such as at the ostium 51. Next, at a balloon inflation step 82, the physician 30 inflates the balloon 40 to contact the lumen wall with the electrode segments 55 over the entire circumference of the lumen.

[0055] Next, at an ablation step 84, the physician 30 connects all of the segments 55 of the electrode 50 and provides RF ablation power to each electrode 50. At a subsequent temperature monitoring step 86, the processor 41 monitors the resulting temperature of each electrode segment 55 using measurements from one or more temperature sensors 57. At a segment temperature check step 88, the processor 41 compares the temperature readings from the sensors 57 on each segment to a preset threshold temperature.

[0056] If the segment temperature is above the preset threshold, which means that the electrode segment is in good contact with the tissue being ablated, the processor controls the switch box 46 to maintain the segment operation as an ablation electrode at an ablation continue step 90. On the other hand, if the segment temperature is below or equal to the preset temperature threshold, the processor 41 controls the switch box 46 to stop supplying RF power to the segment and switch the segment to operate as a sensing electrode at a switch step 92.

[0057] Figure 4 The exemplary flow chart shown in is chosen solely for conceptual clarity. In alternative embodiments, additional steps may be performed, such as processor 41 monitoring the measured impedance of the segment and acting upon the measured impedance, as described above. Figure 4 Methods using a multi-electrode balloon catheter are described, but the principles of the present disclosure are applicable to any catheter having a distal end fitted with multiple electrodes, such as the aforementioned lasso and basket catheters.

[0058] Although the embodiments described herein primarily relate to pulmonary vein isolation, the methods and systems described herein may also be used in other applications requiring definitive occlusion, such as, for example, renal denervation, and generally for ablation of other organs.

[0059] It should therefore be understood that the embodiments described above are cited by way of example, and that the present invention is not limited to what is specifically shown and described above. On the contrary, the scope of the present invention includes combinations and subcombinations of the various features described above, as well as variations and modifications thereof, which will occur to those skilled in the art upon reading the above description and which are not disclosed in the prior art. The documents incorporated by reference into this patent application are considered an integral part of this application, except that if any term defined in these incorporated documents conflicts with a definition explicitly or implicitly given in this specification, only the definition in this specification shall be considered.

Claims

1. A medical system comprising: an expandable distal end of the catheter, the expandable distal end having a plurality of electrodes configured to be placed in contact with tissue in the organ and to apply ablative power to the tissue; and a processor configured to: During application of the ablation power, determining whether physical contact between the plurality of electrodes and tissue satisfies a predefined contact quality; as well as If the physical contact of an electrode of the plurality of electrodes with the tissue does not meet the predefined contact quality, reusing the electrode for electrophysiological (EP) sensing.

2. The system of claim 1, wherein the ablation power comprises at least one of radio frequency (RF) power output by a radio frequency (RF) generator and irreversible electroporation (IRE) pulses output by an irreversible electroporation (IRE) pulse generator.

3. A system according to claim 1, and comprising a switching component configured to switch the electrode between the generator of the ablation power and an electrophysiological (EP) sensing system, wherein the processor is configured to control the switching component to (i) initially connect the electrode to the generator, and (ii) subsequently connect the electrode to the electrophysiological (EP) sensing system so as to reuse the electrode for electrophysiological (EP) sensing.

4. The system of claim 3 , wherein each of the plurality of electrodes comprises a plurality of electrode segments, and wherein the switching component and the processor are configured to individually switch any one of the plurality of electrode segments between the generator and the electrophysiological (EP) sensing system.

5. A system according to claim 1, and comprising a switching component configured to initially connect each of the plurality of electrodes in parallel to the generator of the ablation power and an electrophysiological (EP) sensing system, wherein the processor is configured to control the switching component to subsequently disconnect the electrode from the generator so as to reuse the electrode for electrophysiological (EP) sensing.

6. The system of claim 5, wherein each electrode of the plurality of electrodes comprises a plurality of electrode segments, and wherein the switching assembly and the processor are configured to individually disconnect any one of the plurality of electrode segments from the generator. 7 . The system of claim 1 , wherein the processor is configured to determine whether the physical contact of the electrodes meets the predefined contact quality by evaluating a preset temperature criterion.

8. The system of claim 7, wherein the processor is configured to evaluate the preset temperature criterion by evaluating the measured temperature of the electrode in relation to a preset threshold temperature.

9. The system of claim 1, wherein the processor is configured to determine whether the physical contact of the electrodes meets the predefined contact quality by evaluating a preset impedance criterion.

10. The system of claim 9, wherein the processor is configured to evaluate the impedance criterion by assessing whether a frequency dependence of the impedance indicates that the electrode is in contact with blood or in contact with tissue.

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