Detection and mapping of the phrenic nerve by pacing

Abstract

The invention is entitled "Detecting and mapping phrenic nerve through pacing." The invention relates to an apparatus comprising an interface and a processor. The interface is configured to receive one or more magnetic localization signals from one or more position sensors coupled to one or more body surface patches attached to a body of a patient, the magnetic localization signals being indicative of respective positions of the position sensors. The processor is configured to (i) detect an unintentional stimulation of a phrenic nerve of the patient, the unintentional stimulation occurring due to cardiac pacing applied by an intracardiac electrode in a heart of the patient, (ii) estimate, based on the magnetic localization signals, a motion of one or more of the body surface patches occurring during the detected stimulation of the phrenic nerve, (iii) estimate, based on the estimated motion of the body surface patches, a distance between the pacing electrode and the phrenic nerve, and (iv) send an output derived from the estimated distance to an output device.

Description

Technical Field

[0001] This invention relates generally to invasive medical procedures using medical probes, and more specifically to cardiac pacing and ablation procedures. Background Technology

[0002] The left and right phrenic nerves (which can be collectively referred to as the "phrenic nerves") descend from the neck to the diaphragm, passing between the lungs and the heart, near the heart tissue. The phrenic nerves are involved in the control of breathing. Undesirable movement of the diaphragm caused by diaphragmatic stimulation (a side effect of cardiac pacing) can lead to hiccups and difficulty breathing, and may also trigger diaphragmatic spasms.

[0003] Techniques for detecting unintended pacing of the phrenic nerve have been previously disclosed in patent literature. For example, PCT application WO2018 / 212840 describes a phrenic nerve pacing monitor assembly used during cryoballoon ablation surgery, which monitors the movement of the patient's diaphragm. The assembly includes a pacing detector and a safety system. The pacing detector directly monitors the movement of the patient's diaphragm to detect when phrenic nerve pacing occurs. Additionally, the pacing detector generates a monitor output based on the movement of the patient's diaphragm. The safety system receives the monitor output and, at least in part based on the monitor output, selectively provides an alert when the movement of the patient's diaphragm is atypical. The safety system is configured to provide an alert only when at least one of (i) phrenic nerve pacing and (ii) cryoablation occurs.

[0004] For example, U.S. Patent 6,772,008 describes a cardiac rhythm management device in which an accelerometer is used to detect diaphragmatic contraction or other skeletal muscle contraction associated with the output of a pacing pulse. Upon detection of diaphragmatic contraction, the device can be configured to automatically adjust the pacing pulse energy and / or pacing configuration.

[0005] U.S. Patent Application Publication 2013 / 0109994 describes a system and method for monitoring the function of a patient's phrenic nerve, the system and method comprising: establishing a diaphragm motion value threshold; positioning a diaphragm motion sensor on the external surface of the patient's abdominal cavity; applying a treatment regimen to a tissue region adjacent to the phrenic nerve; measuring the diaphragm motion value using the diaphragm motion sensor; comparing the measured diaphragm motion value with the established diaphragm motion value threshold; and generating an alert in response to the comparison. Summary of the Invention

[0006] Embodiments of the present invention provide an apparatus including an interface and a processor. The interface is configured to receive one or more magnetic positioning signals from one or more position sensors coupled to one or more body surface patches attached to a patient's body, the magnetic positioning signals indicating corresponding positions of the position sensors. The processor is configured to (i) detect involuntary stimulation of the patient's phrenic nerve caused by cardiac pacing applied by an intracardiac electrode in the patient's heart, (ii) estimate, based on the magnetic positioning signals, movement of one or more body surface patches occurring during the detected stimulation of the phrenic nerve, (iii) estimate, based on the estimated movement of the body surface patches, the distance between the pacing electrode and the phrenic nerve, and (iv) send an output obtained based on the estimated distance to an output device.

[0007] In some implementations, the processor is configured to recognize that the distance is below a predefined safety limit and, in response, output a warning to an output device.

[0008] In some implementations, the processor is configured to estimate the distance by applying a predetermined relationship between the estimated motion and the distance.

[0009] In one embodiment, the estimated motion includes the estimated relative motion of at least two of the position sensors relative to each other. In another embodiment, the estimated motion includes the estimated velocity of at least one of the position sensors.

[0010] In some implementations, the estimated motion includes the estimated displacement of at least one of the position sensors.

[0011] In one implementation, the output includes a warning indicating harm to the phrenic nerve.

[0012] In some embodiments, the processor is configured to identify stimulation of the phrenic nerve by recognizing that the frequency of the estimated motion corresponds to the frequency at which a pacing current is applied to the heart. In other embodiments, the processor is also configured to detect unintentional stimulation of the patient's phrenic nerve caused by cardiac ablation.

[0013] In one implementation, the cardiac ablation method is radiofrequency (RF) ablation and / or irreversible electroporation (IRE) and / or pulsed field ablation (PFA).

[0014] According to another embodiment of the invention, a method is also provided, comprising receiving one or more magnetic positioning signals from one or more position sensors coupled to one or more body surface patches attached to a patient's body, the magnetic positioning signals indicating corresponding positions of the position sensors. Involuntary stimulation of the patient's phrenic nerve, the involuntary stimulation occurring due to cardiac pacing applied by an intracardiac electrode in the patient's heart, is detected. Movement of one or more body surface patches occurring during the detected stimulation of the phrenic nerve is estimated based on the magnetic positioning signals. The distance between the pacing electrode and the phrenic nerve is estimated based on the estimated movement of the body surface patches. An output obtained based on the estimated distance is sent to an output device. Attached Figure Description

[0015] The invention will be more fully understood through the following detailed description of embodiments thereof, taken in conjunction with the accompanying drawings, wherein:

[0016] Figure 1 This is a schematic diagram of a system for pacing and ablation of a patient's tissue according to an exemplary embodiment of the present invention, the system being configured to protect the patient's phrenic nerve from ablation damage;

[0017] Figure 2 This is a schematic diagram of the phrenic nerve separated from the catheter tip by the cardiac chamber wall according to an exemplary embodiment of the present invention; and

[0018] Figure 3 The flowchart illustrates, according to an exemplary embodiment of the present invention, a method for estimating the distance from the pacing and ablation electrodes of a catheter to the phrenic nerve prior to ablation of cardiac tissue. Detailed Implementation

[0019] Overview

[0020] When performing cardiac ablation on a patient, it is important to ensure that the phrenic nerve is not damaged by the ablation power (e.g., by overheated nerve tissue).

[0021] Exemplary embodiments of the present invention help prevent damage to the phrenic nerve from ablation power by providing devices and methods for accurately estimating the distance between an ablation power source (e.g., a catheter electrode) and the phrenic nerve.

[0022] In some exemplary embodiments, prior to ablation, the heart is paced, for example using a dual-purpose pacing and ablation probe such as a catheter, to detect tissue location for ablation. The processor, for example, uses the same catheter to measure the resulting electrophysiological activity of the heart and determine whether the tissue at the pacing site is arrhythmogenic.

[0023] To perform bipolar pacing, the catheter includes a pair of electrodes. In addition to stimulating and sensing electrophysiological signals, one electrode in the pair is configured to be driven by an ablation power generator to ablate the tissue site identified as arrhythmogenic. If monopolar pacing is used, a single catheter electrode can be used for both pacing and ablation.

[0024] In some exemplary embodiments, the distance between the ablation electrode and the phrenic nerve is estimated. If the electrode at the arrhythmogenic tissue location identified by pacing surgery is determined to be sufficiently far from the phrenic nerve, the method disclosed in this invention utilizes the same electrode used for pacing to achieve safe electroablation of the tissue location for accurate treatment of the arrhythmia.

[0025] In some exemplary embodiments of the exemplary embodiments disclosed in this invention, as part of pacing and ablation procedures, an impedance-based position tracking system is used to measure the position of electrodes in the heart. This is accomplished using a body surface patch with electrodes. An example of an impedance-based catheter position tracking system is the Active Current Position (ACL) system (manufactured by Biosense-Webster, Irvine, California), which applies an impedance-based position tracking method. Using the ACL method, the processor receives the magnitude of the impedance measured between an electrode fitted at the distal end of the catheter and a surface electrode attached to the patient's skin, indicating the position. Based on both the measured impedance magnitude and the stored position-calibrated impedance magnitude, the system's processor estimates the catheter's position within the patient's organ.

[0026] In an exemplary embodiment disclosed in this invention, one or more patches are further fitted with a magnetic position tracking system (such as CARTO manufactured by Biosense Webster). TM The system uses position sensors. During and / or after each such signal transmission, magnetic position sensors incorporated into the electrodes are used to measure the position of one or more pairs of patch electrodes coupled to the patient's body. If the pacing current stimulates the phrenic nerve, the patient's breathing typically begins to tremble, thus causing the measured position to exhibit a relative motion characteristic of the tremor pattern. The processor (i) identifies unintentional stimulation of the phrenic nerve due to pacing and (ii) receives magnetic positioning signals from sensors on the patches. Based on these signals, the processor estimates the motion of one or more patches that occurred during the unintentional stimulation. Based on the estimated motion of the patches, the processor estimates the distance between the phrenic nerve and the pacing electrodes and generates an appropriate output to the user. The processor is configured to recognize the pattern and, in response, alert the physician that the catheter tip is close to the phrenic nerve.

[0027] In some exemplary embodiments, the processor analyzes the magnetically measured motion of the patch electrodes during pacing and converts the patch motion (e.g., displacement amplitude or velocity) into electrode-nerve distance using a calibration in the form of a function or table. In one embodiment, the processor analyzes the amount of relative motion between the patch electrodes and each other and uses calibration to estimate the corresponding distance between the pacing electrodes and the phrenic nerve. The measured motion can be used to estimate the distance between the electrodes and the phrenic nerve by, for example, using a predetermined relationship between the motions and such distances that can be obtained offline through calibration.

[0028] The processor can compare the estimated distance between the ablation electrode at the location of the arrhythmia-inducing tissue and the phrenic nerve with a predetermined minimum safe distance. If the estimated distance is below the minimum pre-specified value (i.e., below a predefined safety limit), the system can automatically, or the physician can decide, avoid ablation to prevent any potential damage to the phrenic nerve. Alternatively or additionally, the locations where the tremor pattern is identified and quantified can be marked for subsequent examination.

[0029] In yet another exemplary embodiment, the processor is configured to identify stimulation of the phrenic nerve by recognizing that the frequency of the estimated motion corresponds to the frequency at which a pacing current is delivered to the tissue. In another embodiment, the processor is also configured to detect unintentional stimulation of the patient's phrenic nerve caused by cardiac ablation. Ablation methods may include radiofrequency (RF) ablation, irreversible electroporation (IRE), and / or pulsed field ablation (PFA).

[0030] By combining magnetic position tracking and pacing sensing, the combined technology disclosed in this invention can provide accurate information that allows physicians to perform acutely necessary cardiac ablation treatments that might otherwise be discontinued due to uncertainty about the level of harm to nearby phrenic nerves.

[0031] System Description

[0032] Figure 1 This is a schematic diagram of a pacing and ablation system 10 for tissue of a patient 14 according to an exemplary embodiment of the present invention, the system being configured to protect the patient's phrenic nerve from ablation damage.

[0033] System 10 includes an ablation catheter 12, which includes a distal end 13, the distal end of which includes an ablation electrode 33 as seen in illustration 31. Electrode 33 is a dual-purpose electrode that can be used to apply unipolar or bipolar pacing signals, wherein electrode 35 is located just proximal to the distal end 13.

[0034] As shown in the figure, catheter 12 is inserted into patient 14 by physician 16. For example, catheter 12 may be inserted into the patient's vascular system via insertion point 30 and can then be navigated to a specific location within the patient's heart, as further described below. Subsequently, as further described below, catheter 12 is used to determine whether the patient's phrenic nerve is located near that specific location. If the phrenic nerve is not nearby, electrode 33 ablates the patient's arrhythmogenic tissue at that location by delivering an ablation current to the tissue.

[0035] System 10 also includes a plurality of patch electrodes 28 coupled to the body of patient 14. Typically, the patch electrodes 28 are coupled to the exterior of the patient's body, for example, via patches 29 attached to the patient's skin. Figure 1 In the specific embodiment shown, system 10 includes six electrodes, one subset (patch electrodes 28a, 28b and 28c) coupled to the patient's chest, and another subset (patch electrodes 28d, 28e and 28f) coupled to the patient's upper back opposite the patient's chest.

[0036] Each of the patch electrodes 28a-f includes a corresponding magnetic position sensor 40a-f. Typically, each of these sensors 40a-f includes a triaxial coil that generates a position indication signal in the presence of a magnetic field generated by the magnetic position tracking subsystem of system 10. For this purpose, console 18 also includes drive circuitry 38 configured to drive magnetic field generator 36.

[0037] During cardiac pacing using catheter 12, console 18 receives position signals from sensors 40a-f in response to a magnetic field from an external field generator 36. The magnetic field generator 36 is placed at a known location outside the patient 14, for example, under the worktable where the patient lies. These position signals indicate the position of sensors 40a-f in the coordinate system of the magnetic position tracking subsystem. Using the received signals, processor (PROC) 20 calculates the position of sensors 40a-f over time.

[0038] Position and orientation sensing methods using external magnetic fields are implemented in various medical applications, such as the aforementioned CARTO. TM The 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 entire contents of which are incorporated herein by reference, as if listed in full herein.

[0039] Using position sensors 40a-f, the exact positions of the corresponding electrodes 28a-f (which change over time due to the patient 14's breathing) can be accurately determined to monitor the relative movement of electrodes 28a-f at any given time, quantifying the patient 14's breathing pattern during pacing. Using magnetic sensors 40a-f, different estimated positions can be accurately determined, thus improving the detection of chest wall displacement during the patient's breathing.

[0040] Electrodes 28a-f and corresponding sensors 40a-f are typically connected via cable 32 to console 18, which includes one or more units to facilitate the execution of the techniques described herein. For example, console 18 may include processor 20 configured to receive information from the electrodes and corresponding sensors and, based on that information, navigate the catheter and check the catheter's proximity to the phrenic nerve. Console 18 may also include a pacing stimulator 21 configured to generate a pacing current and a radiofrequency (RF) generator 22 configured to generate an RF ablation signal delivered by electrodes 33 of catheter 12 to the patient's tissue.

[0041] Typically, system 10 also includes a display 34 configured to facilitate the execution of the procedure by showing relevant information to physician 16. For example, processor 20 may indicate the location of the catheter on display 34, for instance, by overlaying an icon representing the electrode 33 of the catheter onto an image of the patient's anatomy. Figure 2 The diagram is shown schematically. Alternatively or otherwise, when the processor 20 detects that the electrode 33 of the catheter is near the phrenic nerve, the processor may alert the physician 16 using an appropriate warning on the display 34.

[0042] In some exemplary embodiments, electrode 28 is used to navigate a catheter within a patient's body using impedance-based tracking techniques, such as those described in U.S. Patent 8,456,182 and U.S. Patent Application Publication 2015 / 0141798, the disclosures of which are incorporated herein by reference. Such techniques involve repeatedly probing the position of the catheter (specifically, its distal end) in response to, for example, different corresponding impedances exhibited between electrode 33 of the catheter and each of the electrodes in electrode 28, and then generating an output indicating the probing position. As described above, such output may include the display of relevant icons on display 34 to indicate the current position of the catheter to the physician. Based on this output, the physician can guide the catheter to the desired location.

[0043] More specifically, to determine the position of electrode 33 at any given time, a current of known amplitude is transmitted from electrode 33, and the resulting voltage and / or current are measured at each of the electrodes 28. These voltages and currents vary between electrode 33 and electrode 28 because the amount of impedance tissue between electrode 33 and each of the patch electrodes 28 differs. Therefore, processor 20 can determine the position of the catheter based on the ratio between the measured voltages and / or currents, or the ratio between the impedances implied by these voltages and currents.

[0044] Advantageously, with the support of the magnetic detection technology disclosed in this invention, the same patch electrode 28 used for the navigation catheter can also be used to detect whether the catheter electrode 33 is near the phrenic nerve. U.S. Patent Application Publication 2018 / 0344244 discloses a system and method for identifying the proximity of the catheter tip to the phrenic nerve using patch electrodes, the disclosure of which is incorporated herein by reference.

[0045] Processor 20 typically includes a general-purpose computer having software programmed to perform the functions described herein. This software can be downloaded to the computer electronically via a network, or alternatively or additionally, it can be located and / or stored on a non-transitory tangible medium (such as magnetic storage, optical storage, or electronic storage). Specifically, processor 20 operates as disclosed herein, including... Figure 3 A dedicated algorithm is used to enable the processor 20 to perform the steps disclosed in this invention, as further described below.

[0046] Through pacing detection and mapping of the phrenic nerve

[0047] Figure 2 This is a schematic diagram of the phrenic nerve (25, 27) separated from the catheter tip by the muscular tissue of the cardiac chamber wall and the pericardial sheath of the heart, according to an exemplary embodiment of the present invention. As shown, the electrode 33 on the distal end 13 is located inside the cardiac chamber (e.g., the right atrium 47), at a distance 55 from the right phrenic nerve 27, just outside the heart 26. A similar situation may occur if the catheter is inserted into the left ventricle 45 and brought to a position close to the wall tissue of the left phrenic nerve 25.

[0048] Distance 55 is approximately the thickness of the myocardial wall muscle plus the pericardial spacing and the additional thickness of the capsule, which can be as small as a few millimeters. Performing ablation at any location in the heart chamber without prior estimation of the distance (such as distance 55) can damage the relevant phrenic nerve and can cause serious respiratory disturbances to the patient, for example, due to incorrect nerve signals to the diaphragm 50.

[0049] Therefore, the real-time in-situ estimation of distance 55 disclosed in this invention and the comparison of this distance with a minimum pre-specified safe distance may be crucial for avoiding damage to the phrenic nerve during cardiac ablation using electrode 33.

[0050] Figure 2 The exemplary illustrations shown are chosen purely for clarity of concept; however, actual anatomical structures often vary from patient to patient.

[0051] Figure 3 A flowchart illustrating, according to an exemplary embodiment of the invention, is provided for estimating the distance 55 of the pacing and ablation electrodes 33 of catheter 12 to the phrenic nerve (25, 27) prior to ablation of cardiac tissue. According to the presented embodiment, at pacing step 70, the algorithm performs a process beginning with physician 16 pacing a specific cardiac location within the heart 26 using, for example, electrode 33, to apply a monopolar pacing signal to the tissue.

[0052] At the respiratory pattern measurement step 72, the processor 20 uses position signals from the magnetic sensors 40a-f inside the patch electrode 28 to measure the resulting respiratory pattern (e.g., as confirmed by the movement of one or more body surface patches in the body surface patch), as described above. Next, at the distance estimation step 74, using the measured respiratory pattern (e.g., inter-electrode movement) and calibration between the electrode-nerve distance, the processor 40 estimates the distance 55 between the pacing electrode 33 and the phrenic nerve.

[0053] At arrhythmia diagnosis step 76, if the physician or processor determines that the pacing site is a normal tissue location, i.e., it does not require treatment, then at catheter movement step 78, the physician continues pacing by moving the catheter to another location. The process then returns to pacing step 70.

[0054] On the other hand, if the location is identified as arrhythmogenic tissue, at distance check step 80, the processor compares distance 55 with a minimum pre-specified safe distance. If the estimated distance 55 is determined to be sufficiently large (i.e., above the predefined safe limit), then at step 82, the physician uses the same electrodes used for pacing to ablate the tissue at that location.

[0055] Figure 3 The exemplary flowchart shown is chosen solely for clarity of concept. In alternative embodiments, for example, a bipolar pacing signal may be applied between electrodes 33 and 35. During pacing surgery, an additional reference signal sensing catheter (not shown) may be inserted and placed inside the coronary sinus of the heart 26.

[0056] It should be understood that the above embodiments are cited by way of example, and the invention is not limited to what has been specifically shown and described above. Rather, the scope of the invention includes combinations and sub-combinations 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. Documents incorporated herein by reference are considered an integral part of this application, except that if any terminology defined in such incorporated documents conflicts with the definitions expressly or implicitly given in this specification, only the definitions in this specification shall be considered.

Claims

1. A device for detecting and mapping the phrenic nerve, comprising: An interface configured to receive one or more magnetic positioning signals from one or more position sensors coupled to one or more body surface patches attached to a patient's body, the magnetic positioning signals indicating the corresponding positions of the position sensors; and Processor, the processor being configured to: The detection of unintentional stimulation of the patient's phrenic nerve, the unintentional stimulation being caused by cardiac pacing applied by an intracardiac electrode in the patient's heart; The movement of one or more body surface patches during the detected stimulation of the phrenic nerve is estimated based on the magnetic positioning signal. The distance between the pacing electrode and the phrenic nerve is estimated based on the estimated motion of the body surface patch; as well as The output obtained based on the estimated distance is sent to the output device. The processor is configured to identify stimulation of the phrenic nerve by recognizing that the frequency of the estimated motion corresponds to the frequency at which a pacing current is applied to the heart.

2. The device of claim 1, wherein the processor is configured to identify that the distance is below a predefined safety limit and, in response, output a warning to the output device.

3. The device of claim 1, wherein the processor is configured to estimate the distance by applying a predetermined relationship between the estimated motion and the distance.

4. The device of claim 1, wherein the estimated motion includes the estimated relative motion of at least two of the position sensors relative to each other.

5. The device of claim 1, wherein the estimated motion includes the estimated velocity of at least one of the position sensors.

6. The device of claim 1, wherein the estimated motion includes the estimated displacement of at least one of the position sensors.

7. The device of claim 1, wherein the output includes a warning indicating harm to the phrenic nerve.

8. The device of claim 1, wherein the processor is further configured to detect unintentional stimulation of the phrenic nerve of the patient, the unintentional stimulation occurring due to cardiac ablation.

9. The device of claim 8, wherein the cardiac ablation method comprises one of radiofrequency (RF) ablation, irreversible electroporation (IRE), and pulsed field ablation (PFA).

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