Catheter with multiple sensing electrodes for use as ablation electrodes

Abstract

The invention is entitled "Catheter with multiple sensing electrodes for use as ablation electrodes." A system is disclosed that includes a switching assembly and a processor. The switching assembly is connected to a plurality of electrodes disposed on an inflatable distal end of the catheter and is configured to switch the electrodes between a location tracking system, an electrophysiology (EP) sensing module, and a generator of ablation power. The processor is configured to control the switching assembly to switch the electrodes.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to medical probes, and in particular to cardiac multi-electrode electrophysiology (EP) sensing and ablation catheters. BACKGROUND

[0002] Multi-electrode catheters for tissue sensing and ablation have been previously proposed in the patent literature. For example, U.S. Patent Application Publication 2010 / 0168548 describes a cardiac catheter in a system for electrical mapping of the heart, including a Lasso catheter, having a convex array of perforated electrodes in fluid communication with an irrigation lumen. Position sensors are present on a distal collar portion and a proximal base portion of the catheter. The electrodes are sensing electrodes that can be adapted for pacing or ablation. The convex electrodes safely contact cardiac tissue, thereby forming an electrical connection with little resistance.

[0003] As another example, U.S. Patent 5562720 describes an endometrial ablation device and methods of making and using the same. An electrically conductive inflatable member, such as a balloon, is used as a medium for passing RF current through endometrial tissue to heat the same. Power delivered from a power source to the balloon is selectively applied to a plurality of electrode area segments on the balloon, with each of the segments having a thermistor associated therewith, whereby temperature is monitored and controlled by a feedback arrangement from the thermistors. The selective application of power is provided based on a switching arrangement that provides either monopolar or bipolar energy to the electrodes. SUMMARY

[0004] Embodiments of the present invention provide a system including a switching assembly and a processor. The switching assembly is connected to a plurality of electrodes disposed on an inflatable distal end of the catheter and is configured to switch the electrodes between a position tracking system, an electrophysiology (EP) sensing module, and a generator of ablation power. The processor is configured to control the switching assembly to switch the electrodes.

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

[0006] In some embodiments, each of the electrodes includes a plurality of electrode segments.

[0007] In one embodiment, when a given electrode is connected to the position tracking system or the EP sensing module, the switching assembly and the processor are configured to individually connect each of the electrode segments of the given electrode. When the given electrode is connected to the generator of ablation power, the switching assembly and processor are configured to collectively connect all of the electrode segments of the given electrode.

[0008] In another embodiment, the processor is configured to control whether to use the electrode as a position sensor, as an EP sensor, or as an ablation electrode by evaluating a preset impedance criterion.

[0009] In some embodiments, the processor is configured to evaluate the impedance criterion by assessing whether a frequency dependence of the impedance is indicative of the electrode contacting blood or of the electrode contacting tissue.

[0010] According to embodiments of the present application, there is also provided a method comprising interchangeably switching a plurality of electrodes disposed on an inflatable distal end of a catheter between a position tracking system, an electrophysiological (EP) sensing module, and a generator of ablation power using a switching assembly. The switching assembly is controlled to switch the electrodes using a processor.

[0011] The present application will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings in which: BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a schematic illustration of a balloon catheter-based positioning tracking, electrophysiological (EP) sensing, and ablation system according to embodiments of the present application;

[0013] Figure 2 is a schematic depiction of a balloon catheter according to embodiments of the present application disposed in the region of a pulmonary vein (PV) and its ostium; Figure 1 is a schematic painted side view of a distal end of the balloon catheter of

[0014] Figure 3 is a schematic depiction of a processor-controlled switching box according to embodiments of the present application; Figure 1 is a block diagram schematically describing the functionality of the processor-controlled switching box of

[0015] Figure 4 is a flowchart schematically illustrating a method for interchangeably using the segmented electrodes of the balloon catheter of Figure 2 for position sensing, electrophysiological (EP) sensing, and ablation according to embodiments of the present application. DETAILED DESCRIPTION

[0016] SUMMARY

[0017] To utilize a medical probe, such as an intracardiac radiofrequency (RF) catheter and / or irreversible electroporation (IRE) catheter having a distal end provided with a plurality of electrodes, for effective sensing and ablation, it is important that (a) the distal end be accurately navigated to a tissue location most suitable for electrophysiological (EP) sensing and ablation, and (b) the electrodes provided on the distal end be able to effectively acquire EP signals from the tissue and / or ablate the tissue. For example, when a balloon catheter having a plurality of electrodes is used to treat a cardiac arrhythmia, the balloon must be brought to a cardiac location, such as the ostium of a pulmonary vein (PV), EP signals acquired to verify the cardiac arrhythmia, and the arrhythmogenic tissue ablated, all using the plurality of electrodes.

[0018] Similarly, other multi-electrode catheters, such as a circular mapping catheter (manufactured by Biosense Webster of Irvine, California) or a basket catheter, also need to have their electrodes capable of such sensing and ablation.

[0019] Embodiments of the present invention described below provide techniques for interchangeably using an electrode provided on a distal end for sensing and ablation. In some embodiments, the electrode is initially used as a sensor to track the location of the distal end in order to navigate it to a cardiac tissue location within the heart. Subsequently, the electrode is used for EP sensing. Finally, the electrode is used to apply RF ablation and / or IRE ablation. Typically, the electrode can be used in a spatially selectable manner, where any subset of the electrodes can be switched for any of the above applications at any given time. For example, electrodes that are not in sufficient contact with the tissue can be used for location tracking, while other electrodes are used for EP sensing and subsequent ablation.

[0020] In the context of the present patent application, the term "applying ablation" encompasses both applying RF power and applying IRE pulses. Typically, the ablation power comprises RF power output by a radiofrequency (RF) generator or IRE pulses output by an irreversible electroporation (IRE) pulse generator. However, a single generator can be configured to interchangeably output RF power and IRE pulses.

[0021] In some embodiments, an inflatable multi-electrode catheter (e.g., an inflatable balloon catheter, which is used in the manner of the examples below) is provided, which includes electrodes that are divided into segments (i.e., into electrode segments). In some embodiments, the balloon catheter is provided with ten electrodes placed on the membrane of the balloon. Each of the ten electrodes is divided into four segments, with one or more temperature sensors, such as thermocouples, located on each electrode segment.

[0022] A processor-controlled switch box (also referred to as a switching assembly) is also provided. During navigation of the distal end of a catheter (e.g., a balloon catheter) to a target location for ablation, the disclosed system uses the electrode segments as position sensors for an electrical impedance-based location tracking subsystem, as described below. Once the balloon is determined to be at the target location (using the location tracking subsystem), the processor controlling the switch box switches the EP sensing module or ablation power to at least a portion of the electrode segments.

[0023] In one embodiment, once the catheter is placed at the target location, the processor analyzes the characteristics of the measured impedance, such as, for example, the different frequency dependence of the impedance of blood and tissue, and using the results of this analysis, provides an independent assessment for each electrode segment as to whether the electrode segment is in direct electrical contact (i.e., touching) with cardiac tissue or not (e.g., the electrode segment is mostly immersed in blood).

[0024] The impedance of the electrodes can be determined in any of the modes for which the electrodes are used (i.e., location tracking, EP sensing, and ablation). By using the switch box, each electrode with a frequency-dependent impedance indicative of tissue is subsequently switched by the processor to the EP sensing module or ablation power source. Electrode segments with a frequency-dependent impedance indicative of blood are kept by the processor as position sensing electrodes.

[0025] In some embodiments, the direction of the balloon in space is measured using a magnetic sensor on the catheter near the balloon, as described below, to further assist in optimal placement of the balloon against the ostium, for example, to achieve sufficient electrode contact over the entire circumference of the balloon.

[0026] Generally, the processor is programmed in software containing specific algorithms that enable the processor to perform each of the processor-related steps and functions described above.

[0027] By providing electrode segments that can be switched according to navigation tasks, EP sensing tasks, and ablation tasks, the disclosed segmented electrode sensing and ablation technology can provide safer and more effective diagnosis and treatment. This, in turn, can improve clinical outcomes for, for example, cardiac balloon ablation therapy, such as clinical outcomes for PV isolation to treat arrhythmias.

[0028] System Description

[0029] Figure 1Schematic illustration of a balloon catheter-based positioning tracking, electrophysiology (EP) sensing and ablation system 20 according to an embodiment of the present application. The system 20 includes a catheter 21 fitted at a distal end 22a of a shaft 22 of the catheter with an RF ablation inflatable balloon 40 including a segmented electrode 50 (see inset 25). In the embodiments described herein, the segmented electrode 50 is used to ablate tissue of an ostium 51 of a PV in a heart 26.

[0030] The proximal end of the catheter 21 is connected to a console 24 including an ablation power source 45 capable of delivering IRE power and / or RF power. The console 24 includes a processor 41 that controls a switch box 46 (also referred to as a switching assembly) to switch any one segment of the segmented electrode 50 between acting as a position sensing electrode and acting as an ablation electrode. An ablation protocol including ablation parameters including impedance criteria is stored in a memory 48 of the console 24.

[0031] A physician 30 inserts the distal end 22a of the shaft 22 through a sheath 23 into the heart 26 of a patient 28 lying on a table 29. The physician 30 advances the distal end of the shaft 22 to a target location in the heart 26 and / or deflects the distal end of the shaft relative to the sheath 23 by manipulating the shaft 22 using a manipulator 32 proximal to the proximal end of the catheter. 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 the collapsed configuration, the sheath 23 also serves to minimize trauma to blood vessels along the way to the target location.

[0032] Once the distal end 22a of the shaft 22 has reached the heart 26, the physician 30 retracts the sheath 23 and partially inflates the balloon 40, and further manipulates the shaft 22 to navigate the balloon 40 to the ostium 51 of a pulmonary vein.

[0033] In one embodiment, the physician 30 navigates the distal end of the shaft 22 to the target location by tracking the position of the balloon 40 using impedance measured between the segmented electrode 50 and surface electrodes 38.

[0034] To perform its functions, the processor 41 includes an electrode-impedance-sensing module 47. In this illustrative system, the impedance-sensing module 47 receives electrical impedance signals measured between the segmented electrode 50 and surface electrodes 38, which are seen as attached by wires passing through a cable 37 to the chest of the patient 28. The electrode 50 is connected through a wire passing through the shaft 22 to the processor 41 of the switch box 46 controlling an interface circuit 44 located in the console 24.

[0035] The method for using the aforementioned impedance measurement to track the position of electrodes such as electrode 50 can be implemented in various medical applications, such as in CARTO manufactured by Biosense-Webster (Irvine, California). TM The system is implemented and 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 and copies are provided in the appendix. This method is sometimes referred to as Advanced Catheter Positioning (ACL). In one embodiment, console 24 drives display 27, which displays the tracking position of balloon 40 inside heart 26.

[0036] When at the target location (e.g., at the mouth 51), the physician 30 fully inflates the balloon 40 and positions the segmented electrode 50, positioned above the periphery of the balloon 40, in contact with the tissue at the mouth 51. Next, the physician 30 measures the impedance of each segmented electrode segment, for example, using the impedance sensing module 47, as described above. The processor 41 compares the measured impedance of each segment to a preset threshold impedance. If the segment impedance is lower than or equal to the preset impedance threshold, meaning the electrode segment is in contact with blood rather than with good tissue, the processor 41 controls the switching box 46 to keep the segment operating as a position-sensing electrode. Conversely, if the segment impedance is higher than the preset threshold, meaning the electrode segment is in good tissue contact, the processor controls the switching box 46 to operate the segment as an ablation electrode.

[0037] As further shown in Illustration 25, the distal end 22a includes a magnetic position sensor 39 contained within the distal end 22a, just proximal to the inflatable balloon 40. During navigation of the distal end 22a within the heart 26, the console 24 receives signals from the magnetic sensor 39 in response to a magnetic field from an external field generator 36, for example, to measure the orientation of the ablation balloon 40 within the heart and optionally to display the tracking orientation on the display 27, for example, the orientation relative to an approximate axis of symmetry of the port 51. The magnetic field generator 36 is positioned at a known location outside the patient 28, for example, below the patient's workbench 29. The console 24 also includes drive circuitry 34 configured to drive the magnetic field generator 36.

[0038] The use of external magnetic field orientation sensing methods has been implemented in various medical applications, such as in CARTO manufactured by BiosenseWebster Inc. TMThe system is implemented and is described in detail in U.S. Patents 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612, and 6,332,089, PCT Patent Publication WO 96 / 05768, and U.S. Patent Application Publications 2002 / 0065455A1, 2003 / 0120150A1, and 2004 / 0068178A1, the disclosures of which are incorporated herein by reference in their entirety as if listed in full in this application and copies are provided in the appendix.

[0039] In one implementation, the signal from sensor 39 is also used for the aforementioned CARTO TM The system performs position sensing.

[0040] Processor 41 is typically a general-purpose computer with suitable front-end and interface circuitry 44 for receiving signals from catheter 21, 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, which is programmed to perform the functions described herein. This software can be downloaded electronically to a computer via a network, or alternatively or additionally set and / or stored on a non-transitory tangible medium (such as magnetic storage, optical storage, or electronic storage). Specifically, processor 41 operates as disclosed herein and includes... Figure 4 A dedicated algorithm is used to enable processor 41 to perform the steps disclosed in this invention, as further described below.

[0041] Although Figure 1 Multi-electrode balloon catheters have been described, but the principles of this technique are also applicable to any catheter with a distal end adapted to multiple electrodes, such as the aforementioned lasso catheters and basket catheters.

[0042] A catheter having multiple sensing electrodes that serve as ablation electrodes

[0043] Figure 2 It is deployed in the region of the pulmonary vein (PV) and its orifice 51 according to an embodiment of the present invention. Figure 1 A schematic side view of a balloon catheter. This balloon catheter is used to sense EP signals from the tissue at the mouth 51 to identify arrhythmias and to ablate the tissue at the mouth 51 to isolate the source of the arrhythmia. The balloon 40 has ten segmented electrodes 50 disposed on a membrane 71 of the balloon. IRE and / or RF power can be delivered from the ablation power source 45 independently of each of the four electrode segments 55 of each of the ten electrodes, for example, depending on the level of physical contact between each segment 55 and the tissue during ablation.

[0044] likeFigure 2 As seen in FIG. 5B, electrode segment 55a is not in good contact with tissue. Based on the impedance reading from electrode segment 55a being below or equal to the preset impedance value, processor 41 determines insufficient physical contact of electrode segment 55a. In response, processor 41 controls switch box 46 to keep electrode segment 55a as the sensing electrode.

[0045] On the other hand, electrode segment 55b is in good contact with tissue. Based on the impedance reading from electrode segment 55b being above the preset threshold impedance value, processor 41 determines sufficient physical contact of electrode segment 55a. In response, processor 41 controls switch box 46 to switch electrode segment 55b to be used as an EP sensing electrode or as an ablation electrode.

[0046] In some embodiments, to determine the sufficiency of contact with tissue, the impedance of each electrode segment is monitored by a processor that receives the impedance reading sensed by the electrode segment. The processor uses a preset impedance criterion, such as the relationship of the impedance reading relative to a preset threshold impedance, to determine whether the physical contact between any of the electrodes and the tissue meets a predefined contact quality with the tissue. For example, if the impedance of the electrode segment does not rise above the threshold impedance, the processor determines that the level of contact of the electrode segment with the tissue is insufficient (meaning that EP sensing is sensing a blood signal or that ablation energy will primarily heat blood). In this case, the processor controls the switch box to maintain the electrode segment as a position sensing electrode. On the other hand, if the impedance reading from the electrode segment is above the preset threshold impedance (e.g., above a threshold determined by prior experiments), the processor determines that the electrode segment is in good contact with the tissue, i.e., meets the predefined contact quality criterion, and determines that the tissue can be EP sensed or ablated with the electrode segment. In this case, the switch box switches the electrode segment to connect the electrode segment to the EP sensing module or the ablation power source.

[0047] Techniques for sensing electrode-tissue physical contact using analysis of the frequency response of tissue are described in U.S. Patent Application 15 / 991,291, entitled "Touch Detection by Different Frequency Response of Tissue," filed May 29, 2018, assigned to the assignee of the present patent application and the disclosure of which is incorporated by reference herein as if fully set forth in the present application and provided in the appendix. In one embodiment, the processor can use this method to analyze the acquired intracardiac signals. However, other techniques that use electrical measurements provided by the segmented electrode to assess the level of contact with tissue can be used.

[0048] Figure 2The drawing side view shown in FIG. 6 is chosen by way of example, as other embodiments are possible. For example, in another embodiment, cooling fluid is injected via irrigation holes (not shown) in the electrode 50 to cool the ablated tissue. As another example, a temperature sensor (not shown) adapted on the electrode 50 is used to measure tissue temperature.

[0049] Figure 3 is a block diagram schematically describing the function of the processor-controlled switch box 46 according to an embodiment of the present application. Figure 1 As shown, in response to commands of the processor 41, the switch box 46 connects the electrode segments to the above-described ACL position sensing subsystem of the system 20 to provide position signals for use with the ACL position tracking method, or to the EP sensing module, or to the RF power source to be used as an ablation electrode.

[0050] In another embodiment, when connecting a given electrode to the position tracking system or the EP sensing module, the switch assembly and processor are configured to individually connect each of the electrode segments of the given electrode, while when connecting the given electrode to the generator of the ablation power, the switch assembly and processor are configured to collectively connect all of the electrode segments of the given electrode.

[0051] The block diagram of FIG. 7 is highly simplified Figure 3 to maintain clarity of the presentation. Information from other system elements, such as temperature sensors on the balloon 40, is therefore omitted as not directly contributing to the clear presentation.

[0052] Figure 4 is a flowchart schematically showing a method for interchangeably using Figure 2 segmented electrodes of a balloon catheter for position sensing, electrophysiology (EP) sensing, and ablation according to an embodiment of the present application. According to the presented embodiment, the algorithm performs a process that begins with: at a balloon catheter navigation step 80, the physician 30 navigates the balloon catheter to a target tissue location within a lumen of a patient, such as at the ostium 51, using the electrodes 55 as ACL sensing electrodes.

[0053] Next, at a balloon catheter positioning step 82, the physician 30 positions the balloon catheter at the ostium 51. Next, at a balloon inflation step 84, the physician 30 fully inflates the balloon 40 to bring the lumen wall into contact with the electrode segments 55 over the entire circumference of the lumen.

[0054] Next, using impedance readings of the module 47, the impedance of each of the electrode segments 55 (typically to one of the surface electrodes 38) is measured, and based on impedance criteria, the processor 41 switches some or all of the electrode segments 55 to be used as EP sensing electrodes.

[0055] At switch step 88, after using the electrodes as EP sensors to verify arrhythmia, the processor controls the switch box 46 to operate the segments as ablation electrodes (e.g., connecting the electrodes to the ablation power source 45). At switch step 90, the physician 30 re-switches some or all of the electrode segments 55 to function as EP sensing electrodes to verify that the arrhythmia is eliminated.

[0056] Figure 4 The exemplary flowchart shown in FIG. 6 is chosen for conceptual clarity. In alternative embodiments, additional steps can be performed, such as the processor 41 monitoring the measured contact force of the segments and acting according to the measured contact force.

[0057] While Figure 4 A multi-electrode balloon catheter is described, but the principles of the present technology are also applicable to any catheter having a distal end adapted with multiple electrodes, such as the aforementioned lasso catheter and basket catheter.

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

[0059] It should therefore be understood that the embodiments described above are cited by way of example, and that the present application is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present application includes both combinations and sub-combinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons of ordinary skill in the art upon reading the foregoing description, which are not to be excluded therefrom. Documents incorporated by reference in the present patent application are to be considered an integral part of the application except that to the extent any terms are defined in such incorporated documents in a manner inconsistent with the definitions expressly set forth in the present specification, the terms as expressly used in the present specification take precedence.

Claims

1. A balloon catheter-based positioning, tracking, electrophysiological sensing, and ablation system, comprising: A switching assembly connected to a plurality of electrodes disposed on an expandable distal end of a catheter, the switching assembly being configured to electrically connect the plurality of electrodes to one of a position tracking system, an electrophysiological sensing module, and an ablation power generator; and A processor configured to control the switching component to switch the plurality of electrodes to one of the position tracking system, the electrophysiological sensing module, and the ablation power generator; Wherein, when the impedance reading from one of the plurality of electrodes is lower than or equal to a preset impedance value, the processor is configured to maintain the connection of the electrode among the plurality of electrodes to the position tracking system; and Wherein, when the impedance reading from at least one of the plurality of electrodes is higher than the preset impedance value, the processor is configured to switch the at least one of the plurality of electrodes from being connected to the position tracking system to being connected to the electrophysiological sensing module or the generator of the ablation power.

2. The system according to claim 1, wherein the ablation power includes at least one of radio frequency power output by a radio frequency generator and irreversible electroporation pulse output by an irreversible electroporation pulse generator.

3. The system of claim 1, wherein each of the electrodes comprises a plurality of electrode segments.

4. The system according to claim 3, wherein: When a given electrode is connected to the position tracking system or the electrophysiological sensing module, the switching component and the processor are configured to individually connect each electrode segment of the given electrode. and When the given electrode is connected to the generator of the ablation power, the switching component and the processor are configured to jointly connect all electrode segments of the given electrode.

5. The system of claim 1, wherein the processor is configured to control whether the electrode is used as a position sensor, an electrophysiological sensor, or an ablation electrode by evaluating a preset impedance criterion.

6. The system of claim 5, wherein the processor is configured to evaluate the impedance criterion by assessing whether the frequency correlation of the impedance indicates that the electrode is in contact with blood or that the electrode is in contact with tissue.

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