DETECTING CONTACT AND PROXIMITY BETWEEN ABLATION ELECTRODES BY SENSING CHANGES IN THE VOLTAGE FORM OF NON-ACTIVATED ELECTRODES - Patent application

Abstract

To provide a system for detecting contact and proximity between ablation electrodes.SOLUTION: A system includes a catheter, a pulse generator, and a controller. The catheter includes at least a first electrode, a second electrode and a third electrode, which are disposed at a distal end and configured to contact a tissue within the body. The pulse generator is configured to apply one or more bipolar ablation pulses, for ablating the tissue in contact with the first and second electrodes. The controller is configured to: (i) control the pulse generator to apply the one or more bipolar ablation pulses between the first and second electrodes, (ii) receive a signal indicative of a voltage measured between the third electrode and a reference during the application of the ablation pulses, and (iii) issue a notification in response to detecting that the voltage violates a predefined criterion.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates generally to medical devices, and more particularly to methods and systems for improving bipolar ablation using flexible catheters. [Background technology]

[0002] A variety of techniques have been published for controlling bipolar ablation procedures and electroporation.

[0003] For example, US Patent Application Publication No. 2019 / 0307500 describes an electroporation system, a method of controlling an electroporation system that limits electroporation arcing through an intracardiac catheter, and a catheter for the electroporation system. One method of controlling an electroporation system is disclosed that includes a direct current (DC) energy source, a return electrode connected to the DC energy source, and a catheter connected to the DC energy source. The catheter has at least one catheter electrode. The method includes placing the return electrode near a target location within the body and positioning the catheter electrode adjacent to the target location within the body. A system impedance is determined with the return electrode positioned near the target location and the catheter electrode positioned within the body. The system impedance is adjusted to a target impedance that arcs from the catheter electrode.

[0004] US Patent Application Publication No. 2014 / 0276769 describes a medical device system configured to detect an internal improper energy transmission configuration. This condition may be detected by detecting a condition in which an energy transmission electrode of the medical device system is too close to or in contact with an object, resulting in the electrode being unable to transmit energy properly. For example, if the energy transmission electrode is a first electrode configured in its operative state to transmit energy to body tissue adjacent to the first electrode, but the first electrode inadvertently contacts a second electrode, such contact may cause at least some of the energy transmitted by the first electrode to follow an unintended path away from its intended path to the adjacent tissue. Such a condition may be detected based on an analysis of information obtained from at least the sensing device system. Summary of the Invention [Means for solving the problem]

[0005] One embodiment of the present invention described herein provides a system including a catheter, a pulse generator, and a controller. The catheter is configured for insertion into a patient's body, the catheter including at least a first electrode, a second electrode, and a third electrode disposed at a distal end of the catheter and configured to contact tissue within the body. The pulse generator is configured to apply one or more bipolar ablation pulses between the first electrode and the second electrode to ablate tissue in contact with the first electrode and the second electrode. The controller is configured to (i) control the pulse generator to apply one or more bipolar ablation pulses between the first electrode and the second electrode, (ii) receive a signal indicative of a voltage measured between the third electrode and a reference during application of the ablation pulses, and (iii) issue a notification in response to detecting that the voltage violates a predefined reference.

[0006] In some embodiments, upon detecting that the voltage violates the predefined criteria, the controller is configured to detect that the distance between at least one of (i) the first electrode and the second electrode and (ii) the third electrode is less than a distance threshold. In other embodiments, the pulse generator includes first, second, and third pulse generation circuits having respective output transformers connected between the reference and the first electrode, the second electrode, and the third electrode, respectively, and configured to apply bipolar ablation pulses to the first electrode, the second electrode, and the third electrode, respectively. In yet other embodiments, the controller is configured to disconnect the third electrode from the third output transformer for measurement of a signal indicative of the voltage between the third electrode and the reference.

[0007] According to an embodiment of the present invention, there is further provided a method, the method including inserting into a patient's body a catheter including at least a first electrode, a second electrode, and a third electrode, the electrodes being disposed at a distal end of the catheter for contacting tissue within the body. One or more bipolar ablation pulses are applied between the first electrode and the second electrode to ablate tissue in contact with the first electrode and the second electrode. During application of the ablation pulses, a signal is received indicative of a voltage measured between the third electrode and a reference. In response to detecting that the voltage violates the predefined reference, a notification is issued. [Brief description of the drawings]

[0008] The invention will be more fully understood from consideration of the following detailed description taken in conjunction with the drawings, in which: [Figure 1] 1 is a schematic, pictorial illustration of an ablation system during a cardiac ablation procedure, in accordance with an exemplary embodiment of the present invention. [Figure 2A] 1A-1C are schematic, pictorial illustrations of two shapes of a catheter distal end, according to an exemplary embodiment of the invention. [Figure 2B] 1A-1C are schematic, pictorial illustrations of two shapes of a catheter distal end, according to an exemplary embodiment of the invention. [Diagram 3] FIG. 2 is a schematic, pictorial illustration of a pulse generator for applying an ablation signal, in accordance with an exemplary embodiment of the present invention. [Figure 4] 1 is a flow chart that generally illustrates a method for detecting contact and proximity between ablation electrodes during a bipolar ablation procedure, in accordance with an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Overview Procedures for ablating soft tissue, such as irreversible electroporation (IRE) and radio frequency ablation (RFA) procedures, may involve, for example, applying a bipolar ablation pulse between two ablation electrodes of a catheter inserted into a patient organ to ablate the tissue of interest.

[0010] In principle, it is possible to use a flexible catheter that conforms to the tissue to be ablated. However, in some cases, the flexibility of the catheter may allow undesirable proximity or even physical contact between two or more electrodes of the catheter. Such proximity or contact may, for example, shunt at least a portion of the ablation energy to an undesirable location on the patient's tissue and may also cause inappropriate ablation of the tissue to be ablated.

[0011] The embodiments of the invention described below provide improved techniques for controlling IRE and bipolar RFA procedures while maintaining a safe distance between ablation electrodes of one or more ablation catheters inserted into a patient organ to perform tissue ablation.

[0012] In some embodiments, a system for ablating tissue comprises a catheter, a pulse generator, and a controller, the catheter configured to be inserted into a patient's body and comprising at least a first electrode, a second electrode, and a third electrode disposed at a distal end of the catheter and configured to be placed in contact with tissue to be ablated.

[0013] In some embodiments, the pulse generator is configured to apply one or more bipolar ablation pulses between a first electrode and a second electrode, also referred to herein as the active electrode, to ablate tissue in contact with the first electrode and the second electrode.

[0014] In some embodiments, the controller is configured to control the pulse generator to apply one or more bipolar ablation pulses between the active electrodes. The controller is further configured to receive a signal indicative of a voltage measured between the third electrode and a reference when the ablation pulses are applied to the active electrodes. It is noted that the ablation pulses described above are not applied to the third electrode, and therefore, in this configuration, the third electrode is also referred to herein as a non-active electrode.

[0015] In some embodiments, the controller is configured to issue a notification in response to detecting that the voltage violates a predefined standard.

[0016] Additionally or alternatively, based on the sensed voltages described above, the controller is configured to estimate the distance between a given active electrode and a non-active electrode, and issue a notification if the estimated distance is less than a distance threshold indicating a minimum distance allowed between the given electrodes.

[0017] In accordance with the disclosed technology, the controller is configured to detect when at least a portion of the energy of the ablation pulse is diverted from the active electrode to the inactive electrode and notify a user of the ablation system accordingly. Thus, the disclosed technology improves the quality of bipolar ablation procedures and enables the use of flexible catheters while improving patient safety in IRE and bipolar RFA procedures.

[0018] System Description 1 is a schematic, pictorial illustration of an ablation system 20 during a cardiac ablation procedure, in accordance with one embodiment of the present invention. In some embodiments, a physician 22 performs an ablation procedure on tissue 36 of a patient 24 using an ablation catheter 26, the distal end 28 of which is flexible to conform to the tissue 36 and includes a number of ablation electrodes 30. The ablation procedure may include either an irreversible electroporation (IRE) procedure or a bipolar radiofrequency ablation (RFA) procedure, or possibly a combination of both types of ablation procedures.

[0019] In some embodiments, physician 22 is performing a cardiac ablation procedure using ablation system 20. To begin the procedure, physician 22 inserts catheter 26 into the body of patient 24 and then uses control handle 32 to navigate the catheter to a target site inside or outside of heart 34 of patient 24. Physician 22 then positions distal end 28 in contact with tissue 36 of heart 34, such as myocardium or epicardial tissue.

[0020] In some embodiments, physician 22 selects a pair of electrodes 30a and 30b from among electrodes 30 to perform bipolar ablation. System 20 includes an electrical signal generator (SIG GEN) 38, or a pulse generator, also referred to herein as generator 38 for brevity. Physician 22 controls generator 38 to generate ablation pulses 40 having signal parameters selected to function, for example, as either an IRE signal or an RFA signal, or any suitable combination thereof.

[0021] In some embodiments, the signal 40 is conveyed through the catheter 26 to the ablation electrodes 30a and 30b via different respective channels such that the ablation current flows from one of the electrodes of the pair through the tissue 36 of the patient 24 and back through the other electrode of the pair.

[0022] In some embodiments, the ablation system 20 further comprises a controller (CTRL) 44 configured to receive procedure-appropriate setup parameters 46 from the physician 22 or from another user before and / or during the ablation procedure. Using one or more suitable input devices, such as, for example, a keyboard, mouse, or touch screen, the physician 22 defines the ablation mode (IRE, RFA), parameters of the ablation pulse (e.g., power, duration), and one or more pairs of ablation electrodes 30 to be used for ablation.

[0023] In some embodiments, physician 22 may also input additional setup parameters 46 for ablation pulse 40 using the input devices described above, such as, but not limited to, maximum power, maximum current amplitude, maximum voltage amplitude, duration of the signal, and / or any other relevant parameters. In response to receiving the setup parameters 46, controller 44 is configured to control signal generator 38 to generate signal 40 in accordance with the setup parameters. Controller 44 is further configured to display the setup parameters on display 48, which may comprise a touch screen as described above.

[0024] In some embodiments, the controller 44 is configured to track the position of each of the ablation electrodes 30 within the patient's body during treatment using any suitable tracking technique. For example, the distal end 28 may include at least a magnetic position sensor (not shown) configured to output a position signal indicative of the position of the respective sensor in the presence of an external magnetic field generated by the magnetic field generator 50.

[0025] In some embodiments, based on the position signals, the controller 44 is configured to estimate the position of the distal tip 28 and the electrodes 30. In an alternative embodiment, for each electrode, the controller 44 may receive multiple signals indicative of the respective impedances measured between each electrode and the external electrodes 52 at various different locations disposed on the body surface of the patient 24. In some embodiments, the controller 44 is configured to calculate a ratio between the received impedances to estimate the position of each electrode within the body of the patient 24. As yet another alternative, the controller 44 can use both magnetic-based and impedance-based tracking, for example as described in U.S. Pat. No. 8,456,182, the disclosure of which is incorporated herein by reference.

[0026] In some embodiments, the distal end 28 may have additional sensors, such as, but not limited to, a contact force sensor configured to generate a contact signal indicative of contact between the electrodes 30 and the tissue 36. Based on the position signal and the contact signal, the controller 44 is configured to indicate which ablation electrodes 30 are in contact with the tissue 36. In this example, the electrodes 30a and 30b are in contact with the tissue 36, and in response to a command from the physician 22, the controller 44 is configured to control the signal generator 38 to apply an ablation pulse 40 to the tissue 36 via the electrodes 30a and 30b. It should be noted that in this example, the electrodes 30a and 30b are also referred to herein as "active electrodes," whereas the other electrodes 30 at the distal end 28 are not receiving the ablation pulse 40 and are referred to herein as "non-active electrodes."

[0027] In some embodiments, the controller 44 displays an image 54 of the patient's anatomy on the display 48 and displays the position and orientation of the distal end 28 superimposed on the image 54. Alternatively or additionally, based on signals received from additional sensors disposed at the distal end 28, the controller 44 is configured to track the temperature and / or impedance of the tissue 36 and control the signal generator 38 accordingly.

[0028] In some embodiments, the ablation system 20 includes a control console 56 having a controller 44, a signal generator 38, and a display 48. The catheter 26 is electrically connected to the console 56 via an electrical interface 58, such as a port or socket. Thus, the signal 40 is conveyed to the distal end 28 via the interface 58. Similarly, signals for tracking the position of the distal end 28 and / or signals for tracking the temperature and / or impedance sensed at the tissue 36 may be received by the controller 44 via the interface 58. The magnetic field generator 50 and the external electrode 52 are connected to the console 56 via cables 60 and 62, respectively.

[0029] In some embodiments, the controller 44 typically includes both analog and digital elements. Thus, the controller 44 may include multiple analog-to-digital converters (ADCs) for receiving analog signals from the catheter 26 and the signal generator 38. The controller 44 may further include multiple digital-to-analog converters (DACs) for transmitting analog control signals to the signal generator 38 and other system components. Alternatively, these control signals may be transmitted in digital form, provided that the signal generator 38 is configured to receive digital control signals. The controller 44 typically includes digital filters for extracting signals at given frequencies from the received signals.

[0030] Typically, the functionality of the controller 44 described herein is implemented at least in part in software. For example, the controller 44 may comprise a programmed digital computing device including at least a central processing unit (CPU) and suitable memory, such as any suitable type of random access memory (RAM). Program code, including software programs, and / or data are loaded into the RAM for execution and processing by the CPU. The program code and / or data can be downloaded to the controller in electronic form, for example, over a network. Alternatively or additionally, the program code and / or data may be provided and / or stored on a non-transitory tangible medium, such as a magnetic, optical, or electronic memory. Such program code and / or data, when provided to a processor, results in a machine or special-purpose computer configured to perform the tasks described herein.

[0031] In other embodiments, the controller 44 may comprise a general purpose controller, which is programmed with software to perform the functions described herein. The software may be downloaded to the controller in electronic form, for example over a network, or alternatively or additionally may be provided and / or stored on a non-transitory tangible medium, such as a magnetic, optical or electronic memory.

[0032] This particular configuration of system 20 is provided as an example to illustrate the particular problems addressed by embodiments of the present invention and to demonstrate the application of these embodiments in improving the performance of such systems, however, embodiments of the present invention are not limited to this particular type of exemplary system and the principles described herein may be applied to other types of ablation systems used in medical ablation procedures as well.

[0033] Performing bipolar ablation using a lasso-type catheter 2A and 2B are schematic, pictorial illustrations of two configurations of a distal end 28 of a catheter 26, according to an embodiment of the present invention. Items that are the same as items in FIG. 1 are marked with the same labels.

[0034] In some embodiments, the distal end 28 of the catheter 26 comprises a "lasso" type catheter having multiple electrodes 30 mounted on a flexible arm, which is configured to conform to the shape of the tissue 36 of the patient 24. For example, when ablating pulmonary veins (PV) of the heart 34, the distal end 28 is configured to match the inner diameter of the PV to perform a PV isolation procedure.

[0035] In other embodiments, distal end 28 may comprise any other suitable type of catheter, such as, but not limited to, a multi-arm catheter, such as a basket catheter. Note that in both embodiments, electrodes 30 are disposed on distal end 28 using any suitable configuration, such as along the longitudinal axis of the arms or in different arms of the distal end.

[0036] 2A, in some embodiments, the distal end 28 forms a loop, but none of the electrodes 30 are positioned closely together or in contact with each other.

[0037] Referring now to Figure 2B, in some embodiments, distal end 28 is configured to form a tighter loop as compared to that of Figure 2A, in which electrode 30c is placed in contact with or in close proximity to electrode 30b.

[0038] 2B, when one or more bipolar ablation pulses 40 are applied between electrodes 30a and 30b, at least a portion of the current flowing through electrode 30b may leak (e.g., parasitically) through electrode 30c. As a result of the reduction in power actually applied to tissue 36, bipolar ablation between electrodes 30a and 30b is likely to be inefficient.

[0039] Estimating the proximity between ablation electrodes by sensing the voltage on a non-activated electrode 3 is a schematic, pictorial diagram of a generator 38 according to one embodiment of the present invention. In some embodiments, the generator 38 may be integrated into the console 56 (as shown in FIG. 1 above) or may be located in any other suitable module of the system 20.

[0040] In some embodiments, the generator 38 comprises multiple channels configured to conduct ablation pulses 40 between the pulse generator 38 and each electrode 30 of the catheter 26, as described in detail herein.

[0041] In some embodiments, the generator 38 includes pulse-generation circuits (PGC) 119, 129, 139, and 149 that are connected and configured to apply one or more bipolar ablation pulses 40 to the electrodes 30a, 30b, and 30c, respectively.

[0042] In some embodiments, the PGC 119 comprises a pulse generating apparatus (PGA) 117 connected to an output transformer, referred to herein as transformer 110, which is configured to transfer ablation pulses 40 between the PGA 117 and the electrode 30a of the catheter 26. The PGC 119 further comprises a channel 1 (shown in FIG. 3 as “Ch.1”) made of electrical conductors (e.g., electrical wires or traces) for connecting and disconnecting between the PGC 119 and the electrode 30a of the catheter 26.

[0043] In this embodiment, a first coil of the transformer 110 receives one or more ablation pulses from the PGA 117, and a second coil of the transformer 110, connected to a corresponding channel of the catheter 26 via channel 1, applies one or more ablation pulses 40 to the electrode 30a.

[0044] In some embodiments, the PGC 119 comprises switches 112 and 114 configured to connect and disconnect between the transformer 110 and channel 1, with the switch 114 further configured to connect and disconnect between the transformer 110 and the electrical traces 113. Note that when the switch 114 is closed (as shown in FIG. 3 ), the transformer 110 transfers one or more ablation pulses to the electrode 30a, which is now activated to apply the ablation pulses 40 to the tissue 36.

[0045] In some embodiments, the structure of PGC 119 is repeated in other PGCs of generator 38. For example, PGC 129 comprises (i) a PGA 127 for generating ablation pulses as described above for PGA 117, (ii) a channel 2 having the same characteristics of channel 1, and (iii) a transformer 120 configured to transfer ablation pulses 40 between PGA 127 and electrode 30b via channel 2. Similarly, PGC 139 comprises (i) a PGA 137 for generating ablation pulses as described above for PGA 117, (ii) a channel 3 having the same characteristics of channel 1, and (iii) a transformer 130 configured to transfer ablation pulses 40 between PGA 137 and electrode 30b via channel 3.

[0046] In some embodiments, PGC 149 comprises (i) a PGA 147 for generating ablation pulses as described above for PGA 117, (ii) a channel 4 having the same characteristics as channel 1, and (iii) a transformer 140 configured to transfer ablation pulses 40 between PGA 147 and electrode 30c via channel 4. Note that in the example of Figure 3, generator 38 has ten PCGs (only PGCs 119, 129, 139, and 149 are shown here) for connecting and disconnecting each PGA to and from a respective electrode of catheter 26.

[0047] In other embodiments, generator 38 may have any other suitable number of PGCs for connecting and disconnecting between a corresponding number of electrodes of catheter 26. In yet other embodiments, instead of the PGAs described above, generator 38 may include a single pulse generator (not shown) that is controlled by controller 44 and configured to provide ablation pulses to transformers 110, 120, 130, and 140.

[0048] In some embodiments, the generator includes similar routing and switching configurations for each PGC. For example, switches 122 and 124 are configured to connect and disconnect between transformer 120 and channel 2, switches 132 and 134 are configured to connect and disconnect between transformer 130 and channel 3, and switches 142 and 144 are configured to connect and disconnect between transformer 140 and channel 10.

[0049] In some embodiments, the generator 38 comprises an electrical conductor, referred to herein as the back-patch (BP) 111, which is configured to make an electrical connection between the transformers of the generator 38. The BP 111 may serve as a reference for voltage measurements during application of the ablation pulse 40.

[0050] In some embodiments, generator 38 further comprises switches 118, 128, 138, and 148 for connecting and disconnecting between BP 111 and transformers 110, 120, 130, and 140, respectively. In the example of Figure 3, switches 118 and 138 are closed to connect between BP 111 and transformers 110 and 130, and switches 128 and 148 are opened to disconnect between BP 111 and transformers 129 and 140, respectively.

[0051] In some embodiments, the generator 38 further comprises: (i) a switch 116 for connecting and disconnecting between the transformer 110 and the transformer 120 of adjacent electrodes 30a and 30b; (ii) a switch 126 for connecting and disconnecting between the transformer 120 and the transformer 130 of adjacent electrodes 30 and 30b; (ii) a switch 136 for connecting and disconnecting between the transformer 130 of electrode 30b and the adjacent electrode and an additional transformer (not shown); and (iv) a switch 146 for connecting and disconnecting between the transformer 140 and the transformer 110 via trace 113.

[0052] In some embodiments, the controller 44 is configured to control the generator 38 to apply ablation pulses 40 (i) to electrode 30a via transformer 110 and channel 1, and (ii) to electrode 30b via transformer 130 and channel 3. Note that in this mode of operation, switches 112, 114, and 118 are closed to apply ablation pulses 40 to electrode 30a, and similarly, switches 132, 134, and 138 are closed to apply ablation pulses 40 to electrode 30b.

[0053] In this embodiment, the controller 44 is configured to control the generator 38 to apply a bipolar ablation pulse 40 having an amplitude of about 900V activated in antiphase between channel 1 and channel 3. For example, when channel 1 outputs about +900V to channel 3 of electrode 30a, it outputs about -900V to electrode 30b. Thus, the total amplitude of the bipolar ablation pulse 40 applied between electrodes 30a and 30b is about 1,800V.

[0054] In the context of this disclosure, the term "about" or "approximately" used in connection with any numerical value or range of numerical values ​​indicates a suitable dimensional tolerance that enables a portion of a component or a collection of components to function in accordance with its intended purpose as described herein.

[0055] In some embodiments, during the ablation described above, the voltage amplitude on BP 111 serving the connection between transformer 110 and transformer 130 is substantially zero. Similarly, transformers 120 and 140 are idle and the electrodes connected to channels 2 and 4 are not receiving any ablation pulses.

[0056] In some embodiments, when a bipolar ablation pulse 40 is applied between electrodes 30a and 30b, the controller 44 is configured to receive a signal indicative of the voltage measured between (i) point 145 of the channel 10 connected to electrode 30c and (ii) any suitable reference point on the BP 111, such as reference point 141.

[0057] In some embodiments, when distal end 28 is positioned as shown in FIG. 2A, electrodes 30, 30a, 30b, and 30c are sufficiently far from one another (e.g., about 2 mm or more between any pair of adjacent electrodes). Thus, when about 1800 V is applied between electrodes 30a and 30b (e.g., a voltage of about +900 V is applied to electrode 30a and, simultaneously, about −900 V is applied to electrode 30b), the voltage measured between points 141 and 145 is about 0.

[0058] In some embodiments, when measuring the current through an active electrode, such as electrodes 30a and 30b, the typical impedance measured on each active electrode is typically constant, for example, about 100 Ω.

[0059] In other embodiments, when distal end 28 is positioned as shown in FIG. 2B, electrodes 30b and 30c are in close proximity to one another, for example, less than about 1 mm away, or even in direct contact with one another.

[0060] In some embodiments, in the example of FIG. 2B, when approximately 1800V is applied between electrodes 30a and 30b, a current associated with the ablation pulse 40 can flow in electrode 30b. However, due to the proximity (or physical contact) between electrodes 30b and 30c, a voltage is formed between 30b and 30c. Furthermore, when electrodes 30b and 30c are (unintentionally) placed in contact with each other, the surface area of ​​the "combined" electrodes (including electrodes 30b and 30c) is greater than the surface area of ​​electrode 30b. Thus, the impedance measured on the combined electrodes is substantially different from the approximately 100Ω measured in the example described in FIG. 2A above. Furthermore, the measured current through the combined electrodes is substantially different from the measured current through electrode 30b in the example described in FIG. 2A above.

[0061] Additionally or alternatively, the voltage measured between points 141 and 145 is substantially greater than zero. For example, (i) when the distance between electrodes 30b and 30c is about 1 mm, the voltage measured between points 141 and 145 is about 400 V, and (ii) when electrodes 30b and 30c are in direct contact, the voltage measured between points 141 and 145 is greater than about 800 V.

[0062] In some embodiments, controller 44 is configured to issue a notification in response to detecting that the voltage measured between points 141 and 145 violates a predefined criterion. For example, controller 44 is configured to maintain a threshold value for the voltage measured between points 141 and 145 and to issue a notification if the measured voltage exceeds (i.e., is greater than) the threshold voltage. Additionally or alternatively, controller 44 is configured to maintain a predefined pulse shape for the voltage measured between points 141 and 145. The pulse shape may have a predefined waveform, for example, the waveform may include voltage amplitude plotted as a function of measurement time.

[0063] In some embodiments, controller 44 is configured to maintain a preassigned inter-electrode distance threshold (e.g., about 1.5 mm), also referred to herein as the distance threshold. Based on the voltage measured between points 141 and 145, controller 44 is configured to detect whether the distance between electrodes 30b and 30c is less than the distance threshold.

[0064] In some embodiments, the measured voltage increases as the distance between electrodes 30b and 30c decreases, and therefore controller 44 is configured to estimate the distance between electrodes 30b and 30c based on the measured voltage. For example, when the measured voltage is between about 400V and 550V, the distance between electrodes 30b and 30c is less than about 1 mm.

[0065] Additionally or alternatively, controller 44 is configured to issue a notification in response to detecting that the current flowing through an active electrode (in this example, electrode 30b) and / or the current flowing through a non-active electrode (such as electrode 30c) violates respective predefined criteria.

[0066] In some embodiments, the controller 44 is configured to disconnect the electrode 30c from the transformer 140, for example by opening the switches 142 and 144, in order to measure a signal indicative of the voltage between the points 141 and 145.

[0067] FIG. 4 is a flow chart that generally illustrates a method for detecting contact and proximity between ablation electrodes 30b and 30c during a bipolar ablation procedure, in accordance with one embodiment of the present invention.

[0068] The method begins with a catheter insertion step 100 in which a catheter 26 is inserted into the heart 34 or any other suitable organ within the body of the patient 24. As described above in FIGS. 1-3 , the catheter 26 includes at least electrodes 30 a, 30 b, and 30 c disposed at a distal end 28 for placement in contact with tissue 36 of the heart 34.

[0069] In a tissue ablation step 102, the controller 44 controls the generator 38 to apply one or more bipolar ablation pulses 40 between electrodes 30a and 30b to ablate tissue 36 in contact with electrodes 30a and 30b, as described above in Figures 1, 2A, and 2B.

[0070] In signal receiving step 104, when applying the ablation pulse 40, the controller 44 receives a signal indicative of the voltage measured between points 141 and 145, which constitutes the voltage between electrode 30c and BP111, which serves as a reference, as described in FIG. 3 above.

[0071] In a first decision step 106, the controller 44, which maintains one or more thresholds for the electrical parameters, such as a voltage threshold, checks whether the measured parameter exceeds the respective threshold. Additionally or alternatively, the controller 44 may maintain a distance threshold and estimate the distance between the electrodes 30b and 30c based on the measured voltage. In some embodiments, the controller 44 checks whether the estimated distance is less than or greater than the distance threshold.

[0072] In some embodiments, in step 106, controller 44 may detect that the voltage measured between points 141 and 145 is greater than a voltage threshold and / or that the estimated distance is less than a distance threshold. In such embodiments, the method proceeds to an alert and adjustment step 108 with a notification issued by controller 44 to cease application of the bipolar ablation pulse 40. Additionally or alternatively, controller 44 may automatically control generator 38 to cease application of the bipolar ablation pulse 40 between electrodes 30a and 30b.

[0073] In some embodiments, the controller 44 may also issue a notification to the physician 22 to adjust the position of the electrode at the distal end 28 relative to the tissue 36 because the active electrode (e.g., electrode 30b) and the inactive electrode (e.g., electrode 30c) are touching each other or are positioned too close to each other.

[0074] In some embodiments, after adjusting the position of the electrode at the distal end 28 relative to the tissue 36, the controller 44 may estimate the need to apply additional bipolar ablation pulses 40 to the tissue 36, and if more ablation is required, the method loops back to step 102 to apply an ablation pulse as described above.

[0075] In other embodiments, in step 106, controller 44 may detect that the voltage measured between points 141 and 145 is less than a voltage threshold and / or that the estimated distance is greater than a distance threshold. In such embodiments, the method proceeds to a continue ablation step 109, where controller 44 controls generator 38 to continue applying one or more bipolar ablation pulses 40 between electrodes 30a and 30b according to the ablation plan.

[0076] In a second decision step 110, the controller 44 checks whether the ablation procedure is complete, for example, when sufficient bipolar ablation pulses 40 have been applied to the tissue 36. If the ablation procedure is not complete, the method loops back to step 109. If the ablation is complete, the method proceeds to a catheter extraction step 112, which ends the method, such that the physician 22 extracts the catheter 26 from the body of the patient 24.

[0077] Although the embodiments described herein are primarily directed to bipolar ablation procedures using flexible catheters with multiple electrodes, such as lasso-type catheters, the methods and systems described herein can also be used in other applications, such as bipolar ablation procedures using other types of catheters to maintain a predetermined distance between the electrodes of the catheter. Additionally, the embodiments described herein can also be used in various types of electroporation procedures, such as, but not limited to, irreversible electroporation and electrosurgical procedures.

[0078] It will therefore be understood that the above-described embodiments are cited by way of example, and that the present invention is not limited to what has been particularly shown and described above. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described in the above specification, as well as variations and modifications thereof that would occur to one skilled in the art upon reading the foregoing description, and that are not disclosed in the prior art. Documents incorporated by reference into this patent application are to be considered as part of this application, except that if any term is defined in these incorporated documents in a manner that is inconsistent with the definition expressly or impliedly given herein, then only the definition in this specification shall be considered.

[0079] [Embodiment] (1) A system for detecting contact and proximity between ablation electrodes by sensing changes in a voltage profile of a non-active electrode, the system comprising: a catheter configured for insertion into a patient's body, the catheter including at least a first electrode, a second electrode, and a third electrode disposed at a distal end of the catheter and configured to contact tissue within the body; a pulse generator configured to apply one or more bipolar ablation pulses between the first electrode and the second electrode to ablate the tissue in contact with the first electrode and the second electrode; 1. A system comprising: a controller configured to: (i) control the pulse generator to apply the one or more bipolar ablation pulses between the first electrode and the second electrode; (ii) receive a signal indicative of a voltage measured between the third electrode and a reference during application of the ablation pulses; and (iii) issue a notification in response to detecting that the voltage violates a predefined reference. (2) The system of embodiment 1, wherein when detecting that the voltage violates the predetermined criterion, the controller is configured to detect that a distance between (i) at least one of the first electrode and the second electrode and (ii) the third electrode is less than a distance threshold. (3) The system of embodiment 1, wherein the pulse generator includes first, second, and third pulse generating circuits having respective output transformers connected between the reference and the first electrode, the second electrode, and the third electrode, respectively, and configured to apply the bipolar ablation pulses to the first electrode, the second electrode, and the third electrode, respectively. (4) The system of embodiment 3, wherein the controller is configured to disconnect the third electrode from the third output transformer for measuring the signal indicative of the voltage between the third electrode and the reference. (5) A method for detecting contact and proximity between ablation electrodes by sensing a change in a voltage profile of a non-activated electrode, the method comprising: inserting a catheter into a patient's body, the catheter including at least a first electrode, a second electrode, and a third electrode disposed at a distal end of the catheter for contacting tissue within the body; applying one or more bipolar ablation pulses between the first electrode and the second electrode to ablate the tissue in contact with the first electrode and the second electrode; receiving a signal indicative of a voltage measured between the third electrode and a reference during application of the ablation pulse; and issuing a notification in response to detecting that the voltage violates a predefined standard.

[0080] (6) The method of embodiment 5, wherein detecting that the voltage violates the predetermined criteria includes detecting that a distance between (i) at least one of the first electrode and the second electrode and (ii) the third electrode is less than a distance threshold. (7) The method of embodiment 5, wherein applying one or more bipolar ablation pulses comprises applying the bipolar ablation pulses to the first electrode, the second electrode, and the third electrode, respectively, in a pulse generator including first, second, and third pulse generation circuits having respective output transformers connected between the reference and the first electrode, the second electrode, and the third electrode, respectively. (8) The method of embodiment 7, wherein receiving the signal includes disconnecting the third electrode from the third output transformer for measuring the signal indicative of the voltage between the third electrode and the reference.

Claims

1. 1. A system for detecting contact and proximity between ablation electrodes by sensing changes in a voltage profile of a non-active electrode, the system comprising: a catheter configured for insertion into a patient's body, the catheter including at least a first electrode, a second electrode, and a third electrode disposed at a distal end of the catheter and configured to contact tissue within the body; a pulse generator configured to apply one or more bipolar ablation pulses between the first electrode and the second electrode to ablate the tissue in contact with the first electrode and the second electrode; 1. A system comprising: a controller configured to: (i) control the pulse generator to apply the one or more bipolar ablation pulses between the first electrode and the second electrode; (ii) receive a signal indicative of a voltage measured between the third electrode and a reference during application of the one or more bipolar ablation pulses; and (iii) issue a first warning notification to a physician to stop application of the one or more bipolar ablation pulses or a second warning notification to adjust a position of the distal end of the catheter relative to the tissue if the voltage is greater than a threshold voltage.

2. 1. A system for detecting contact and proximity between ablation electrodes by sensing changes in a voltage profile of a non-active electrode, the system comprising: a catheter configured for insertion into a patient's body, the catheter including at least a first electrode, a second electrode, and a third electrode disposed at a distal end of the catheter and configured to contact tissue within the body; a pulse generator configured to apply one or more bipolar ablation pulses between the first electrode and the second electrode to ablate the tissue in contact with the first electrode and the second electrode; 1. A system comprising: a controller configured to: (i) control the pulse generator to apply the one or more bipolar ablation pulses between the first electrode and the second electrode; (ii) receive a signal indicative of a voltage measured between the third electrode and a reference during application of the one or more bipolar ablation pulses; and (iii) control the pulse generator to stop application of the one or more bipolar ablation pulses if the voltage is greater than a threshold voltage.

3. 1. A system for detecting contact and proximity between ablation electrodes by sensing changes in a voltage profile of a non-active electrode, the system comprising: a catheter configured for insertion into a patient's body, the catheter including at least a first electrode, a second electrode, and a third electrode disposed at a distal end of the catheter and configured to contact tissue within the body; a pulse generator configured to apply one or more bipolar ablation pulses between the first electrode and the second electrode to ablate the tissue in contact with the first electrode and the second electrode; 1. A system comprising: a controller configured to: (i) control the pulse generator to apply the one or more bipolar ablation pulses between the first electrode and the second electrode; (ii) receive a signal indicative of a voltage measured between the third electrode and a reference during application of the one or more bipolar ablation pulses; and (iii) issue a first warning notification to a physician to stop application of the one or more bipolar ablation pulses or a second warning notification to a physician to adjust a position of the distal end of the catheter relative to the tissue if a distance between the second electrode and the third electrode estimated based on the voltage is less than a distance threshold.

4. 1. A system for detecting contact and proximity between ablation electrodes by sensing changes in a voltage profile of a non-active electrode, the system comprising: a catheter configured for insertion into a patient's body, the catheter including at least a first electrode, a second electrode, and a third electrode disposed at a distal end of the catheter and configured to contact tissue within the body; a pulse generator configured to apply one or more bipolar ablation pulses between the first electrode and the second electrode to ablate the tissue in contact with the first electrode and the second electrode; 1. A system comprising: a controller configured to: (i) control the pulse generator to apply the one or more bipolar ablation pulses between the first electrode and the second electrode; (ii) receive a signal indicative of a voltage measured between the third electrode and a reference during application of the one or more bipolar ablation pulses; and (iii) control the pulse generator to stop application of the one or more bipolar ablation pulses when a distance between the second electrode and the third electrode estimated based on the voltage is less than a distance threshold.

5. 5. The system of claim 1, wherein the pulse generator includes first, second, and third pulse generating circuits having respective output transformers connected between the reference and the first electrode, the second electrode, and the third electrode, respectively, and configured to apply the one or more bipolar ablation pulses to the first electrode, the second electrode, and the third electrode, respectively.

6. 6. The system of claim 5, wherein the controller is configured to disconnect the third electrode from the output transformer of the third pulse generating circuit for measuring the signal indicative of the voltage between the third electrode and the reference.

7. A method of operating a controller, wherein the controller detects contact and proximity between ablation electrodes by sensing a change in a voltage profile of a non-activated electrode, the method comprising: receiving, by the controller, a signal indicative of a voltage measured between a third electrode disposed at the distal end of the catheter and a reference while one or more bipolar ablation pulses are applied by a pulse generator between a first electrode and a second electrode disposed at the distal end of the catheter under control of the controller to ablate tissue in contact with the first and second electrodes; and issuing a first warning notification to a physician to stop application of the one or more bipolar ablation pulses or a second warning notification to a physician to adjust the position of the distal end of the catheter relative to the tissue when the voltage is greater than a threshold voltage.

8. A method of operating a controller, wherein the controller detects contact and proximity between ablation electrodes by sensing a change in a voltage profile of a non-activated electrode, the method comprising: receiving, by the controller, a signal indicative of a voltage measured between a third electrode disposed at the distal end of the catheter and a reference while one or more bipolar ablation pulses are applied by a pulse generator between a first electrode and a second electrode disposed at the distal end of the catheter under control of the controller to ablate tissue in contact with the first and second electrodes; and the controller controlling the pulse generator to cease application of the one or more bipolar ablation pulses when the voltage is greater than a threshold voltage.

9. A method of operating a controller, wherein the controller detects contact and proximity between ablation electrodes by sensing a change in a voltage profile of a non-activated electrode, the method comprising: receiving, by the controller, a signal indicative of a voltage measured between a third electrode disposed at the distal end of the catheter and a reference while one or more bipolar ablation pulses are applied by a pulse generator between a first electrode and a second electrode disposed at the distal end of the catheter under control of the controller to ablate tissue in contact with the first and second electrodes; and issuing a first warning notification to a physician to stop applying the one or more bipolar ablation pulses or a second warning notification to a physician to adjust a position of the distal end of the catheter relative to the tissue when a distance between the second electrode and the third electrode estimated based on the voltage is less than a distance threshold.

10. A method of operating a controller, wherein the controller detects contact and proximity between ablation electrodes by sensing a change in a voltage profile of a non-activated electrode, the method comprising: receiving, by the controller, a signal indicative of a voltage measured between a third electrode disposed at the distal end of the catheter and a reference while one or more bipolar ablation pulses are applied by a pulse generator between a first electrode and a second electrode disposed at the distal end of the catheter under control of the controller to ablate tissue in contact with the first and second electrodes; and controlling the pulse generator to stop applying the one or more bipolar ablation pulses when a distance between the second electrode and the third electrode estimated based on the voltage is less than a distance threshold.

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