Monopole impedance monitoring for diagnosing lead stability

Abstract

A method of operating a cardiac rhythm management (CRM) system includes: cyclically calculating, by a medical device of the CRM system, an impedance between a housing electrode included in a housing of the medical device and each of a plurality of pacing electrodes, where the plurality of pacing electrodes includes a left bundle pacing electrode configured to be placed in a left bundle of a subject; comparing the calculated impedance with one or more specified impedance values; and generating an alert regarding pacing electrode placement in response to the calculated impedance corresponding to the pacing electrode differing from the one or more specified impedance values by a predetermined threshold impedance value.

Description

[0001] Priority requirements

[0002] This application claims priority to U.S. Provisional Application No. 63 / 452,335, filed March 15, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0003] This document generally relates to cardiac rhythm management systems, and particularly, but not limited to, methods, systems, and devices for automatically monitoring the stability of cardiac pacing leads. Background Technology

[0004] The heart is the center of the human circulatory system and comprises an intrinsic electromechanical system that performs two main pumping functions. The left side of the heart (comprising the left atrium (LA) and left ventricle (LV)) draws oxygenated blood from the lungs and pumps it to the body's organs, providing them with the oxygen they need for metabolism. The right side of the heart (comprising the right atrium (RA) and right ventricle (RV)) draws deoxygenated blood from the body's organs and pumps it to the lungs, where it is oxygenated. These pumping functions are caused by the contraction of the heart's myocardium. In a normal heart, the sinoatrial (SA) node (the heart's natural pacemaker) generates intrinsic electrical impulses that propagate through the electrical conduction system to various regions of the heart to stimulate the myocardial tissue of the heart muscle. For example, intrinsic electrical impulses originating from the SA node propagate through the atrioventricular (AV) node located between the RA and RV. From the AV node, the electrical impulses use a specialized intrinsic conduction system to reach the ventricular myocardium, causing ventricular contraction. This specialized conduction system includes the His bundle, right and left conduction branches extending along the septum between the RV and LV, and Purkinje fibers that contact the myocardial tissue of the ventricle.

[0005] In a normal electrical conduction system, the inherent delay in the propagation of electrical impulses results in synchronized contractions of different parts of the heart, leading to effective pumping function. Heart disease can alter these normal intrinsic conduction pathways. Blockages in electrical conduction, or other abnormalities in conduction, can cause asynchronous cardiac contractions, resulting in poor hemodynamics, which may reduce the amount of blood supplied to the heart and other parts of the body. For example, blockage of electrical impulses in the left or right bundle branch can lead to asynchrony between the ventricles (RV and LV) of the heart. Blockage of normal conduction pathways can cause intrinsic electrical impulses to conduct along alternating pathways, which can cause one ventricle to contract slightly later than the other. In such cases of cardiac dysfunction, cardiac pacing therapy can be provided to resynchronize the contraction of the heart's ventricles. Summary of the Invention

[0006] Methods, systems, and devices for monitoring the efficacy of pacing electrodes used to treat cardiac conduction disorders are disclosed. Example 1 includes a subject matter (such as a method of operating a medical device) that includes cyclically calculating the impedance between a housing electrode included in the housing of the medical device and each of a plurality of pacing electrodes, wherein the plurality of pacing electrodes includes a left bundle branch pacing electrode configured to be placed in the left bundle branch of a subject; comparing the calculated impedance with one or more specified impedance values; and generating an alarm regarding the placement of the pacing electrode in response to a difference of a predetermined threshold impedance value between the calculated impedance corresponding to the pacing electrode and one or more specified impedance values.

[0007] In Example 2, the subject matter according to Example 1 may optionally include: cyclically calculating the impedance between the housing electrode and each electrode of the implantable lead, the implantable lead including a plurality of pacing electrodes, the plurality of pacing electrodes including a left bundle branch pacing electrode; and generating an alarm regarding the placement of the left bundle branch pacing electrode when the calculated impedance of the left bundle branch pacing electrode is greater than a predetermined threshold impedance value than one or more specified impedance values.

[0008] In Example 3, the subject matter according to Example 2 may optionally include: cyclically calculating the impedance between the housing electrode and another lead electrode configured for bipolar pacing with the left bundle branch pacing electrode; and generating an alarm regarding the placement of the implantable lead when the calculated impedance of at least one of the left bundle branch pacing electrode and the other lead electrode is greater than a predetermined threshold impedance value by one or more specified impedance values.

[0009] In Example 4, the subject matter according to Example 3 may optionally include generating an alarm when the calculated impedance between the housing electrode and the left bundle branch pacing electrode is less than a predetermined threshold impedance value than a specified impedance.

[0010] In Example 5, the subject matter described according to one or any combination of Examples 1-4 may optionally include: the calculation of the activation impedance of the medical device in response to the medical device determining the presence of the left bundle branch pacing electrode.

[0011] In Example 6, the subject matter described in Example 5 may optionally include: after determining the presence of a left bundle branch pacing electrode, the medical device activates a cyclic calculation of impedance for a specified duration.

[0012] In Example 7, the subject matter described according to one or any combination of Examples 1-6 may optionally include: initiating a capture threshold test in response to the calculated impedance differing from a specified impedance by more than a predetermined threshold impedance value; and generating an alarm in response to a detected change in the capture threshold and the calculated impedance differing from the specified impedance by a predetermined threshold impedance value.

[0013] In Example 8, the subject matter described according to one or any combination of Examples 1-7 may optionally include: initiating a sensing threshold test in response to the calculated impedance differing from a specified impedance by more than a predetermined threshold impedance value; and generating an alarm in response to a detected change in the sensing threshold and the calculated impedance differing from the specified impedance by a predetermined threshold impedance value.

[0014] In Example 9, the subject matter described according to one or any combination of Examples 1-8 may optionally include: measuring the baseline impedance value between the housing electrode and the left bundle branch pacing electrode by a medical device.

[0015] Example 10 includes a subject matter (such as a device) comprising: a treatment circuit configured to provide electrical pacing energy to the left bundle branch of a subject when operatively connected to a plurality of pacing electrodes, including a left bundle branch pacing electrode; a housing for housing the electronic circuitry of the device and including housing electrodes formed on the housing; a sensing circuit configured to sense at least one of a voltage or current relative to the housing electrode of each of the pacing electrodes; and a control circuit operatively coupled to the treatment circuit and the sensing circuit. The control circuit includes an impedance measurement circuit configured to measure the impedance between the housing electrode and each of the pacing electrodes. The control circuit is configured to: cyclically initiate impedance measurements between the housing electrode and each of the plurality of pacing electrodes, including the left bundle branch pacing electrode; compare the calculated impedance with one or more specified impedance values; and generate an alarm regarding pacing electrode placement in response to a difference of a predetermined threshold impedance value between the calculated impedance corresponding to the pacing electrode and one or more specified impedances.

[0016] In Example 11, the subject matter according to Example 10 may optionally include control circuitry configured to: cyclically initiate impedance measurements between the housing electrode and each lead electrode of the implantable lead, the implantable lead including a left bundle branch pacing electrode as a lead tip electrode; and generate an alarm regarding the placement of the implantable lead in response to an impedance measured for the left bundle branch pacing electrode being greater than a predetermined threshold impedance value by one or more specified impedance values.

[0017] In Example 12, the subject matter according to Example 11 may optionally include control circuitry configured to: cyclically initiate impedance measurements between a housing electrode and a ring electrode for implantable leads, the ring electrode being configured for bipolar pacing with a left bundle branch pacing electrode; and generate an alarm regarding the placement of the implantable lead in response to an impedance measured for at least one of the left bundle branch pacing electrode and the ring electrode being greater than a predetermined threshold impedance value by one or more specified impedance values.

[0018] In Example 13, the subject matter according to one or both of Examples 11 and 12 may optionally include control circuitry configured to generate an alarm when the calculated impedance between the housing electrode and the left bundle branch pacing electrode is less than a predetermined threshold impedance value than a specified impedance.

[0019] In Example 14, the subject matter described according to one or any combination of Examples 11-13 may optionally include control circuitry configured to: determine the presence of a pacing electrode configured for placement in the left bundle branch; and, upon determining the presence of the pacing electrode, initiate cyclically impedance measurements for a specified duration.

[0020] In Example 15, the subject matter described according to one or any combination of Examples 10-14 may optionally include control circuitry configured to: initiate a capture threshold test in response to a calculated impedance differing from a specified impedance by more than a predetermined threshold impedance value; and generate an alarm in response to a detected change in the capture threshold and the calculated impedance differing from the specified impedance by the predetermined threshold impedance value.

[0021] In Example 16, the subject matter described according to one or any combination of Examples 10-15 may optionally include: initiating a sensing threshold test in response to the calculated impedance differing from a specified impedance by more than a predetermined threshold impedance value; and generating an alarm in response to a detected change in the sensing threshold and the calculated impedance differing from the specified impedance by a predetermined threshold impedance value.

[0022] In Example 17, the subject matter described according to one or any combination of Examples 10-16 may optionally include control circuitry configured to: initiate a baseline impedance measurement between the housing electrode and the left bundle branch pacing electrode; and use the measured baseline impedance value as a specified impedance value.

[0023] Example 18 includes a subject matter (such as a heart rhythm management system) or may optionally be combined with one or any combination of Examples 1-17 to include such a subject matter, comprising: an implantable lead configured for placement in the right ventricle of a subject, the implantable lead having a plurality of pacing electrodes, including a left bundle branch pacing electrode configured for placement in the left bundle branch of the subject; and a medical device for coupling to the implantable lead. The medical device includes a housing to house the electronic circuitry of the device and includes a housing electrode formed on the housing; a treatment circuit configured to provide electrical pacing energy to the left bundle branch pacing electrode; a sensing circuit configured to sense at least one of a voltage or current of each of the pacing electrodes relative to the housing electrode; and a control circuit operatively coupled to the treatment circuit and the sensing circuit including an impedance measurement circuit. The impedance measurement circuit is configured to measure the impedance between the housing electrode and each of the pacing electrodes. The control circuit is configured to: cyclically initiate impedance measurements between each of the housing electrode and the pacing electrodes (including the left bundle branch pacing electrode) of the lead; compare the calculated impedance with one or more specified impedance values; and generate an alarm regarding the placement of the implantable lead in response to a predetermined threshold impedance value differing between the calculated impedance corresponding to the pacing electrode and one or more specified impedances.

[0024] In Example 19, the subject matter according to Example 18 optionally includes an implantable lead comprising a loop electrode configured to pace the right ventricle of a subject. Control circuitry is configured to generate an alarm regarding the placement of the implantable lead when the calculated impedance of at least one of the left bundle branch pacing electrode and the loop electrode is greater than a predetermined threshold impedance value by one or more specified impedance values.

[0025] In Example 20, the subject matter according to Example 19 may optionally include control circuitry configured to generate an alarm regarding the placement of an implantable lead when the calculated impedance between the housing electrode and the left bundle branch pacing electrode is less than a predetermined threshold impedance value than a specified impedance.

[0026] This summary is intended to provide an overview of the subject matter of this application. It is not intended to provide an exclusive or exhaustive explanation of the invention. Detailed descriptions are included to provide further information regarding the subject matter of this patent application. Attached Figure Description

[0027] Figure 1 A portion of an example of a Cardiac Rhythm (CRM) system is shown.

[0028] Figure 2This image shows a portion of an example of an implantable medical device (IMD) within a CRM system, as well as a portion of the environment in which the IMD operates.

[0029] Figure 3 An implantable lead with a retractable spiral for anchoring the lead end is shown.

[0030] Figure 4 This is a block diagram of an example IMD (Information Management Device) in a CRM system.

[0031] Figure 5 This is a flowchart illustrating an example of a method for manipulating an IMD.

[0032] Figures 6A-6B This is an example of electrode placement for Left Bundle Branch Area Pacing (LBBAP) and an illustration of an electrophysiological record sensed using this electrode.

[0033] Figures 7A-7B This is another example of placing an LBBAP electrode and an illustration of an electrograph sensed using that electrode.

[0034] Figures 8A-8B This is a further example of placing the LBBAP electrode and an illustration of an electrograph sensed using that electrode.

[0035] Figure 9 This is a flowchart of another example of a method for manipulating IMD. Detailed Implementation

[0036] Conventional right ventricular (RV) pacing delivers pacing pulses to the RV, providing relief, for example, to subjects with blockages in the normal conduction pathway of the right ventricle. Conduction system pacing (CSP) is direct pacing of the heart's conduction system, resulting in greater physiological activation of the ventricles in lieu of conventional right ventricular pacing. CSP treatment allows pacing at multiple locations within the conduction system (e.g., the His bundle and left bundle branch), and pacing at these locations can result in various types of capture.

[0037] Figure 1A portion of an example CRM system 100 and a portion of an environment in which the CRM system 100 can be used are shown. The CRM system 100 can be configured to include an implantable medical device (IMD) 102 and an external system 104, as well as communication links, such as a telemetry link 106. The IMD 102 may include an electronic unit coupled to the heart 110 of a subject 112 via a cardiac lead 108 or additional leads. Examples of the IMD 102 may include, but are not limited to, pacemakers, pacemaker / defibrillators, cardiac resynchronization devices, cardiac remodeling control devices, and cardiac monitors. In the example, the IMD 102 may be configured to monitor the health of the heart 110 and identify one or more abnormalities associated with the heart 110. The IMD 102 may take necessary actions, such as stimulating one or more portions of the heart 110 via the lead 108, to treat the one or more abnormalities.

[0038] In the example, external system 104 may include an external device 107 configured to communicate bidirectionally with IMD 102 (e.g., via telemetry link 106). For example, external device 107 may include a programmer to program IMD 102 to provide one or more treatments to heart 110. In the example, external device 107 may be programmed to detect the presence of conduction block in the left bundle branch (LBB) of heart 110 and prevent asynchronous contraction of heart 110 by providing cardiac resynchronization therapy (CRT) to heart 110.

[0039] In the example, external device 107 can be configured to transmit data to IMD 102 via telemetry link 106. Examples of such transmitted data may include programming instructions for IMD 102 to acquire physiological data, perform at least one self-diagnostic test (such as for device operating status), or deliver at least one treatment or any other data. In the example, IMD 102 can be configured to transmit data to external device 107 via telemetry link 106. Such transmitted data may include real-time physiological data acquired by or stored in IMD 102, treatment history data, operating status of IMD 102 (e.g., battery status or lead impedance), etc. Telemetry link 106 may include an inductive telemetry link or a far-field radio frequency telemetry link.

[0040] In this example, external device 107 may be part of a patient management system that may include other devices, such as a remote system 114 for remotely programming IMD 102. In this example, remote system 114 may be configured to include a server 116 that can communicate with external device 107 via a telecommunications network 118, such as to access IMD 102 for remote monitoring of the health of heart 110 or adjustment of parameters associated with one or more treatments.

[0041] Figure 2 A portion of another example of an IMD 102 of a CRM system and a portion of the environment in which the IMD 102 operates are shown. The IMD 102 may include a hermetically sealed housing 204 and a head 206 extending from the housing 204. The head 206 may include one or more containers, such as the proximal end for receiving one or more cardiac leads (collectively referred to herein as leads 108), such as leads 108A, leads 108B, and leads 108C. The distal end of leads 108 may be coupled to electrodes, such as electrodes disposed on or around the heart 110, for the purpose of providing pacing energy, defibrillation energy, or both. The electrodes may also be used to sense the electrical activity of the heart 110, including electrical activity related to the contraction of the atria or ventricles.

[0042] like Figure 2 As shown, the heart 110 includes a right atrium (RA) 208, a left atrium (LA) 210, a right ventricle (RV) 212, a left ventricle (LV) 214, and a coronary sinus 216 extending from the RA 208. In this example, the lead 108A may be an intravascular RA lead that extends from the superior vena cava (SVC) into the RA 208 and may include electrodes such as a loop electrode 218 and a tip electrode 220, for example for sensing signals or delivering pacing therapy to the RA 208, or both.

[0043] In the example, lead 108C may be an intravascular right ventricular (RV) lead that extends from the SVC into RA 208 and then into RV 212. Lead 108C may be configured to include defibrillation coil electrodes 226, such as to deliver high-energy shock therapy to the subject. RV lead 108C may include electrode pairs 232 for sensing signals, delivering pacing therapy, or both. RV lead 108C may be configured to achieve resynchronization of RV 212.

[0044] In the example, lead 108B may be a left bundle branch (LBB) region lead that extends into RA 208, into RV 212, and then into LBB region 230. In the example, LBB region lead 108B may include a tip electrode 222 and a loop electrode 224, which can be used to deliver electrical stimulation energy and sense intrinsic electrocardiographic signals.

[0045] The IMD 102 may include a housing electrode 211 formed on a housing 204 of the IMD 102. The IMD 102 may provide unipolar pacing using any pacing electrode with leads and the housing electrode 211, or it may provide bipolar pacing using electrode pairs. The IMD 102 may use unipolar sensing to sense intrinsic electrocardiographic signals using the housing electrode 211 and the leaded electrode, or it may use bipolar sensing to sense intrinsic electrical signals using bipolar electrode pairs.

[0046] To provide treatment for conduction disorders of LV 214, electrical stimulation pulses can be delivered to the stimulation site within LBB region 230. Left bundle branch area pacing (LBBAP) involves placing the LBBAP lead 108B into the LBB or surrounding tissue on the left side of the ventricular septum. Bipolar LBBAP can be delivered using a tip electrode 222 as the pacing cathode and a ring electrode 224 as the pacing anode. Monopolar pacing can be delivered using a tip electrode 222 as the pacing cathode and a shell electrode 211 as the pacing anode. The extent of this LBB pacing region 230 can be two to ten times deeper than the depth of a conventional right ventricular lead, depending on the thickness of the septum.

[0047] Compared to RV pacing leads, the septal depth of LBBAP leads increases, therefore impedance is a key focus during implantation and subsequent monitoring throughout the device's lifespan. Measuring the impedance at the electrode site can provide information about the LBBAP electrode placement. For example, because it is desired to place the LBBAP tip electrode 222 between the left side of the ventricular septum and the endocardium of LV 214, there is a possibility of perforation into the LV 214 cavity. As LBBAP lead 108B is implanted, the impedance at the tip electrode 222 increases with the septal depth of electrode 222. A sudden drop in impedance during LBBAP lead 108B positioning (e.g., a drop of more than 20% within a predetermined time frame) can indicate perforation into the LV cavity, which then requires lead repositioning.

[0048] Unipolar or bipolar impedance can be measured using an IMD 102. The unipolar impedance for tip electrode 222 can be measured by applying a known current between tip electrode 222 and housing electrode 211. The voltage generated by the applied current can be measured, and the impedance from tip electrode 222 to housing electrode 211 can then be calculated using Ohm's law. The unipolar impedance of any electrode used in a CRM system can be measured similarly. Bipolar impedance is measured by applying a known current between tip electrode 222 (typically a pacing cathode) and ring electrode 224 (typically a pacing anode) and measuring the voltage generated between tip electrode 2222 and ring electrode 224.

[0049] Monitoring the unipolar impedance of the tip electrode 222 during implantation, rather than the bipolar impedance, accurately tracks the positioning of the pacing cathode without causing confusion in the advancement of the pacing anode, which could occur, for example, if the pacing anode (e.g., the ring electrode 224) is not fully exposed from the delivery catheter or if the anode is embedded in the septum.

[0050] Following lead implantation, the impedance of one or more electrodes of the lead remains a key indicator of lead placement stability. A significant decrease in the unipolar impedance of the tip electrode 222 that occurs during patient movement after implantation can indicate positional changes in the pacing lead 108B, such as the tip electrode 222 moving into the LV cavity. A sharp increase in impedance can also provide information.

[0051] Figure 3 An implantable lead 308 with a retractable helix 340 for anchoring the lead tip is shown. The helix may be part of the tip electrode of the pacing lead. The helix 340 retracts during initial positioning to allow for easier lead insertion and is exposed when the lead is positioned to anchor it in the LBB. Figure 3 The top shows a spiral 340 extending from the original implantation site. Figure 3 The bottom shows that spiral 340 later contracts. A contracted or partially contracted spiral can cause a sharp increase in the unipolar impedance of the electrode. This may require redeploying spiral 340.

[0052] Back Figure 2 Changes in the position of the pacing anode can also be detected using unipolar impedance. For example, a sudden increase in the impedance of the ring electrode 224 can indicate that the ring electrode 224 has moved from inside the RV cavity to inside the septum. If the ring electrode 224 is positioned in the septum at the implantation site, a sudden decrease in impedance can indicate that the electrode 224 has moved outside the septum. Figure 2 A sudden change in the unipolar impedance of any electrode can provide information about the stability of the leads including the electrode.

[0053] Therefore, monitoring electrode impedance beyond the implantation stage and clinical settings can provide information about lead stability throughout the lifespan of the implanted CRM system. The measured impedance is unipolar impedance and is independent of the programmed pacing configuration. This means that unipolar impedance is monitored even if the electrodes are programmed for a bipolar configuration. Therefore, the measured impedance does not necessarily reflect the programmed electrode configuration of the CRM system.

[0054] Figure 4 It is a CRM system (e.g.) Figure 1 This is a block diagram of an example portion of an IMD 102 of a CRM system 100, which can monitor the impedance of the electrodes of the CRM system to monitor the stability of the CRM system leads. The IMD 102 may include cardiac signal sensing circuitry 404, treatment circuitry 406, and control circuitry 408. The IMD 102 may be connected to one or more implantable cardiac leads including implantable electrodes. The IMD 102 includes a housing to house the electronic circuitry of the IMD 102, and the housing includes at least one housing electrode. In some examples, the IMD 102 is a leadless medical device and implantable electrodes for sensing and pacing are included on the housing of the IMD 102. The electrodes include at least one LBB electrode for placement in or near the patient's LBB.

[0055] Treatment circuit 406 provides electrical pacing energy to the patient's LBB when operatively connected to the pacing electrodes of a system including LBBAP electrodes. Sensing circuit 404 includes one or more sensing amplifiers to sense the LBBAP electrodes (e.g., Figure 2 The control circuit 408 may include one or both of the voltage or current signals at the electrodes of the system (LBBAP electrodes 222 and 224). The control circuit 408 may include a digital signal processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a microprocessor, or other type of processor that interprets or executes instructions in software or firmware. In some examples, the control circuit 408 may include a state machine or sequencer implemented in hardware circuitry. The control circuit 408 may include any combination of hardware, firmware, or software. The control circuit 408 includes one or more circuits for performing the functions described herein. The circuitry may include software, hardware, firmware, or any combination thereof. For example, the circuitry may include instructions in software executed on the control circuit 408. Multiple functions may be performed by one or more circuits. The control circuit 408 includes impedance measurement circuitry 410 to measure the impedance between the housing electrode and each of the pacing electrodes.

[0056] Figure 5It is an implantable medical device that operates a CRM system (e.g.) Figure 4 The flowchart illustrates an example of a method 500 for monitoring the stability of the system's electrodes throughout the system's lifespan (IMD 102). To monitor stability, the unipolar impedance of all implanted electrodes is monitored throughout the device's lifespan.

[0057] At 505, control circuitry 408 cyclically initiates impedance measurements between the housing electrode and each of the pacing electrodes in the CRM system; including the unipolar impedance of the LBBAP electrode. If the LBBAP electrode is included in an implantable LBB lead, monitoring the unipolar impedance of the LBBAP electrode provides additional insight into lead stability. In some examples, the unipolar impedance measurement feature of the device can be enabled or disabled by the clinician (e.g., using...). Figure 1 External device 107 (as described above). In some examples, if the LBBAP electrode configuration is selected by the clinician, the external device provides a prompt (e.g., on the external device's display) to activate the impedance measurement feature. In some examples, control circuitry 408 is capable of detecting the presence of the LBBAP electrode (e.g., by detecting the presence of the LBB pacing lead). Upon detection of the LBB pacing configuration, control circuitry 408 automatically enables impedance measurement.

[0058] When enabled, the impedance measurement circuit 410 measures the unipolar impedance of the electrode. A known current or voltage can be applied to the electrode and the resulting voltage or current can be sensed using the sensing circuit 404. The impedance circuit 410 uses the current and voltage to calculate the impedance of the electrode.

[0059] Impedance can be measured at all electrodes, or only at specified electrodes (e.g., only the LBBAP electrode). In some examples, control circuitry 408 does not immediately initiate unipolar impedance measurement upon activation. Instead, it waits a specified duration after implantation before initiating impedance measurement. This gives the patient time to move using the CRM system and allows for assessment of lead stability using the patient's activity. The duration can be a programmed default time or a time specified by the clinician. The time interval between impedance measurements can also be a default time or a time specified by the clinician.

[0060] At block 510, control circuitry 408 compares the calculated impedance to a specified impedance value to see if the unipolar impedance of the electrode has undergone a drastic change since implantation. In some examples, the impedance to the electrode is determined at or shortly after implantation to allow for impedance settling, as tissue around the implant may leave scars. The measured value can be a baseline value used as the specified impedance value. In some examples, the clinician enters the value into the system at implantation or near the start of the device's lifespan. The clinician can specify one or both of the high impedance limit and low impedance limit as the specified impedance value to which the calculated impedance will be compared. In some examples, the clinician specifies an incremental (delta) impedance value and monitors changes in the incremental impedance value from the baseline impedance value.

[0061] At block 515, control circuitry 408 generates an alarm regarding electrode placement in response to a calculated impedance for the electrode differing from a specified impedance by a predetermined threshold impedance value. The alarm may be a flag displayed the next time IMD 102 is queried by an external device. In some examples, the external device displays (e.g., using the external device's user interface) the unipolar impedance of all electrodes measured. The alarm may include the external device altering the display of the impedance value (e.g., by highlighting the impedance value using a specific color) to draw the clinician's attention to the impedance value. In some examples, the alarm is a signal sent to the patient device as notification that a problem may exist and one or more leads should be evaluated.

[0062] According to some examples, control circuit 408 generates an alarm in response to a sudden large increase in the unipolar impedance of the LBBAP electrode that is greater than a predetermined threshold. As explained previously herein, this could be due to the contraction of the helical portion of the LBBAP cathode, the cathode retracting into the myocardial tissue, or the LBBAP anode (e.g., a ring electrode) entering the septal tissue. In some examples, control circuit 408 generates an alarm in response to a sudden large decrease in the unipolar impedance of the LBBAP electrode that is less than a predetermined threshold or is a decrease greater than a predetermined increment. As explained previously herein, this could be due to the LBBAP cathode moving from the septum to the LV cavity or the LBBAP anode moving from the septum to the RV cavity. Monitoring the impedance trends of multiple electrodes can improve the accuracy of monitoring.

[0063] According to some examples, the unipolar impedance measurement feature of the IMD 102 can be combined with other diagnostics. For example, the IMD 102 may be able to monitor changes in the sensing threshold of intrinsic cardiac signals or changes in the pacing capture threshold. The capture threshold is the threshold voltage required to initiate depolarization in cardiac tissue. The IMD 102 can further examine changes in one or both of the sensing and capture thresholds when detecting impedance changes against the electrodes. This additional examination is useful for improving the accuracy of detecting whether the electrode position has changed. Control circuitry 408 generates an alarm when a change in impedance and a detected change in the capture or sensing threshold are detected. For example, control circuitry 408 will run an automatic threshold test and measure the value of the R wave when a sudden change in unipolar impedance is detected. Control circuitry 408 may generate an alarm regarding lead stability when an approximately 20% decrease in the amplitude or magnitude of the R wave and an approximately 20% increase in the pacing threshold are detected.

[0064] Figure 6A , Figure 7A and Figure 8A The placement of LBBAP lead 108B in the LBB region is shown. For clarity, the dimensions in the accompanying figures may be somewhat exaggerated. Figure 6A The placement of the tip electrode at the end of the LBBAP lead 108B in the LBB is shown (e.g. Figure 2 (The tip electrode 222). The electrode is positioned in the LBB portion of the septum. Figure 7B It is the sensing circuit 404 for Figure 6A An example of an electrograph of electrode position sensing.

[0065] Figure 7A The LBBAP electrode with perforated LV endocardium is shown. Figure 7B It is the sensing circuit 404 for Figure 7A An example of an electrogram sensed by electrode position. The signal morphology changes, and the amplitude of the R-wave decreases. Control circuit 408 can perform signal processing on the sensed electrogram to detect changes in one or both of the morphology of the sensed electrogram and the amplitude of the R-wave.

[0066] Figure 8A The LBBAP electrode is shown, with only the endocardium of the spiral-perforated LV and the injured tissue behind the spiral. Figure 8B It is the sensing circuit 404 for Figure 8A An example of an electrophoretic mapping for electrode position sensing. (Compared to...) Figure 6BCompared to the previous example, the signal morphology changed and the amplitude of the R-wave decreased. The detection of changes in the electrogram can be combined with the detection of changes in unipolar impedance to detect positional changes in the implanted lead. An alarm generated by the IMD 102 draws attention to this change, and the clinician can determine whether the lead needs to be repositioned.

[0067] Figure 9 This is a flowchart illustrating an example of a method for operating the IMD of a CRM system to monitor the stability of one or more LBBAP electrodes. At block 905, the unipolar impedance (unipolar Z) of one or both of the LBBAP cathode and anode electrodes is measured cyclically. In some examples, the measurements are performed according to a schedule programmed into the IMD. The unipolar impedance of one or more LBBAP electrodes can be measured as part of cyclic measurements of all electrodes in the CRM system.

[0068] At block 910, it is determined whether there is a sudden change in the measured value of the unipolar impedance. As explained earlier in this document, a sudden change can be a sudden increase or a sudden decrease in impedance. A change in impedance can be considered “sudden” if the impedance value changes by more than a predetermined threshold impedance value within a specific time period. If no sudden change is detected, the method returns to block 905 to await the next unipolar impedance measurement.

[0069] At block 915, if a sudden change in unipolar impedance is detected, the IMD runs one or both of the automatic pacing threshold test and the automatic sensing threshold test. At block 920, if a significant change exists in either the pacing threshold or the sensing threshold, the IMD generates an alarm regarding the stability of one or more LBBAP electrodes. The alarm may include one or more of the measured unipolar impedance, the measured pacing threshold, and the measured sensing threshold.

[0070] Improper positioning of cardiac leads can reduce the effectiveness of cardiac treatments delivered to patients. This method, system, and device can provide effective monitoring of implanted cardiac leads to detect whether the leads are stable or have shifted and require repositioning.

[0071] Additional notes

[0072] The above detailed description includes references to the accompanying drawings, which form part of the detailed description. The drawings illustrate, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are also referred to herein as “examples.” All publications, patents, and patent documents mentioned in this document are incorporated herein by reference in their entirety, as if individually incorporated by reference. In the event of any inconsistency between the usage of this document and those documents incorporated by reference, the usage in the incorporated reference shall be considered supplementary to the usage in this document; in the case of irreconcilable inconsistencies, the usage in this document shall prevail.

[0073] In this document, as is common in patent literature, the terms “a” or “one” are used to include one or more, independent of any other instances or uses of “at least one” or “one or more.” In this document, the term “or” is used to refer to a non-exclusive “or,” such that “A or B” includes “A, but without B,” “B, but without A,” and “A and B,” unless otherwise stated. In the appended claims, the terms “including” and “in which” are used as concise English equivalents to the respective terms “comprising” and “wherein.” Furthermore, in the following claims, the terms “including” and “comprising” are open-ended, meaning that a system, apparatus, article, or process including elements other than those listed after such terms in the claims is still considered to fall within the scope of the claims. Additionally, in the following claims, the terms “first,” “second,” and “third,” etc., are used merely as labels and are not intended to impose numerical requirements on their objects.

[0074] The method examples described herein may be implemented, at least in part, by a machine or computer. Some examples may include a computer-readable or machine-readable medium encoded with instructions operable to configure an electronic device to perform the methods described in the examples above. Implementations of such methods may include code, such as microcode, assembly language code, or high-level language code. Such code may include computer-readable instructions for performing various methods. The code may form part of a computer program product. Further, the code may be tangibly stored on one or more volatile or non-volatile computer-readable media during execution or at other times. These computer-readable media may include, but are not limited to, hard disks, removable disks, removable optical discs (e.g., optical discs and digital video discs), magnetic tape cartridges, memory cards or sticks, random access memories (RAMs), read-only memories (ROMs), and the like. In some examples, a carrier medium may carry the code implementing the method. The term "carrier medium" may be used to refer to a carrier wave on which the code is transmitted.

[0075] The above description is intended to be illustrative and not restrictive. For example, the above examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments may be used by those skilled in the art upon review of the above description. The abstract is provided to comply with 37 C.FR § 1.72(b) to allow the reader to quickly determine the nature of the technical disclosure. It is understood at the time of submission that it is not to be construed as limiting the scope or meaning of the claims. Furthermore, in the above detailed description, various features may be grouped together to simplify this disclosure. This should not be construed as meaning that features of the disclosure not claimed are essential to any claim. Rather, the inventive subject matter may lie in fewer than all features of a particular disclosed embodiment. Therefore, the following claims are incorporated herein by reference, wherein each claim stands independently as a separate embodiment. The scope of the invention should be determined by reference to the appended claims together with the full scope of their legally claimed equivalents.

Claims

1. A method comprising: The impedance between a housing electrode included in the housing of the medical device and each of a plurality of pacing electrodes is calculated cyclically by the medical device, wherein the plurality of pacing electrodes includes a left bundle branch pacing electrode configured to be placed in the left bundle branch of the subject. Compare the calculated impedance with one or more specified impedance values; and An alarm is generated regarding the placement of the pacing electrode in response to a calculated impedance corresponding to the pacing electrode differing from one or more specified impedance values ​​by a predetermined threshold impedance value.

2. The method according to claim 1, include: Specifically, cyclically calculating the impedance includes cyclically calculating the impedance between the housing electrode and each electrode of the implantable lead, the implantable lead including the plurality of pacing electrodes, the plurality of pacing electrodes including the left bundle branch pacing electrode; and The alarm generation includes generating an alarm regarding the placement of the left bundle branch pacing electrode when the calculated impedance of the left bundle branch pacing electrode is greater than the predetermined threshold impedance value than one or more specified impedance values.

3. The method according to claim 2, comprising: in, The cyclic calculation of the impedance includes cyclically calculating the impedance between the housing electrode and another lead electrode, the other lead electrode being configured for bipolar pacing with the left bundle branch pacing electrode; as well as The alarm is generated when the calculated impedance of at least one of the left bundle branch pacing electrode and the other lead electrode is greater than the predetermined threshold impedance value by the one or more specified impedance values, thus generating an alarm regarding the placement of the implantable lead.

4. The method according to claim 3, wherein, The alarm is generated when the calculated impedance between the housing electrode and the left bundle branch pacing electrode is less than the predetermined threshold impedance value than the specified impedance.

5. The method according to any one of claims 1-4, comprising: In response to the medical device determining the presence of the left bundle branch pacing electrode, the medical device activates the impedance calculation.

6. The method according to any one of claims 1-5, comprising: A capture threshold test is initiated in response to the calculated impedance differing from the specified impedance by more than the predetermined threshold impedance value; as well as The alarm generated regarding the placement of the pacing electrode includes generating the alarm in response to a detected change in the capture threshold and a calculated impedance that differs from the specified impedance by a predetermined threshold impedance value.

7. The method according to any one of claims 1-6, comprising: A sensing threshold test is initiated in response to the calculated impedance differing from the specified impedance by more than the predetermined threshold impedance value; as well as The alarm generated regarding the placement of the pacing electrode includes generating the alarm in response to a detected change in the sensing threshold and a calculated impedance that differs from the specified impedance by a predetermined threshold impedance value.

8. An apparatus comprising: A treatment circuit configured to provide electrical pacing energy to the left bundle branch of a subject when operatively connected to a plurality of pacing electrodes, including a left bundle branch pacing electrode. A housing for housing the electronic circuitry of the device and including housing electrodes formed on the housing; A sensing circuit configured to sense at least one of the voltage or current of each of the pacing electrodes relative to the housing electrode; as well as A control circuit, operatively coupled to the treatment circuit and the sensing circuit, and including an impedance measurement circuit configured to measure the impedance between the housing electrode and each of the pacing electrodes; The control circuit is configured as follows: The impedance measurement between the housing electrode and each of the plurality of pacing electrodes, including the left bundle branch pacing electrode, is initiated cyclically. Compare the calculated impedance with one or more specified impedance values; and An alarm is generated regarding the placement of the pacing electrode in response to a calculated impedance corresponding to the pacing electrode differing from one or more specified impedances by a predetermined threshold impedance value.

9. The apparatus according to claim 8, wherein, The control circuit is configured as follows: The impedance measurement between the housing electrode and each lead electrode in the implantable lead, which includes a left bundle branch pacing electrode as a lead tip electrode, is initiated cyclically. as well as An alarm is generated regarding the placement of the implantable lead in response to the impedance measured for the left bundle branch pacing electrode being greater than a predetermined threshold impedance value than one or more specified impedance values.

10. The apparatus according to claim 9, wherein, The control circuit is configured as follows: The impedance measurement between the housing electrode and the implantable leaded ring electrode is cyclically initiated, the ring electrode being configurable for bipolar pacing with the left bundle branch pacing electrode; as well as An alarm is generated regarding the placement of an implantable lead in response to a measured impedance for at least one of the left bundle branch pacing electrodes and the ring electrode being greater than a predetermined threshold impedance value than the one or more specified impedance values.

11. The apparatus according to claim 9 or 10, wherein, The control circuit is configured to generate the alarm when the calculated impedance between the housing electrode and the left bundle branch pacing electrode is less than the predetermined threshold impedance value than the specified impedance.

12. The apparatus according to any one of claims 9-11, wherein, The control circuit is configured as follows: Determine the presence of the pacing electrode configured for placement in the left bundle branch; and After confirming the presence of the pacing electrode, impedance measurements are initiated cyclically for a specified duration.

13. The apparatus according to any one of claims 8-12, wherein, The control circuit is configured as follows: A capture threshold test is initiated in response to the calculated impedance differing from the specified impedance by more than a predetermined threshold impedance value; and The alarm is generated in response to a detected change in the capture threshold and a calculated impedance that differs from the specified impedance by the predetermined threshold impedance value.

14. The apparatus according to any one of claims 8-13, wherein, The control circuit is configured as follows: A sensing threshold test is initiated in response to the calculated impedance differing from the specified impedance by more than the predetermined threshold impedance value; and The alarm is generated in response to a detected change in the sensing threshold and a calculated impedance that differs from the specified impedance by the predetermined threshold impedance value.

15. The apparatus according to any one of claims 8-14, wherein, The control circuit is configured as follows: Initiate baseline impedance measurement between the housing electrode and the left bundle branch pacing electrode; and Use the measured baseline impedance value as the specified impedance value.

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