System for pre-atrial-period contraction load estimation

Abstract

Systems and methods are disclosed for a mobile medical device that includes a cardiac signal sensing circuit configured to sense a cardiac signal representative of cardiac activity of a patient when connected to an electrode, and a control circuit. The control circuit is configured to monitor cardiac depolarization in the sensed cardiac signal, detect a bimodal distribution of the heart rate of the patient, identify cardiac depolarization intervals that are shorter than a predetermined interval threshold, identify preatrial contractions (PACs) of normal conduction and abnormal conduction in the sensed cardiac signal, and count the number of conducted PACs, and generate an alert related to the patient's PAC load based on the number.

Description

[0001] Priority requirements

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 528,563, filed July 24, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0003] This document relates generally to medical devices, and more specifically to systems, methods, and apparatus for estimating the conduction of atrial premature contraction load in patients. Background Technology

[0004] Mobile medical devices, including implantable, subcutaneous, insertable, wearable, or one or more other medical devices, can monitor, detect, or treat various conditions, including heart failure (HF) and atrial fibrillation (AF). Mobile medical devices may include sensors for sensing physiological information from a patient and one or more circuits for using the sensed physiological information to detect one or more physiological events or to transmit the sensed physiological information or detected physiological events to one or more remote devices. Frequent patient monitoring can provide early detection of deteriorating patient conditions, including worsening heart failure or atrial fibrillation.

[0005] Accurate identification of patients or patient groups at increased risk of future adverse events can control the mode or feature selection or resource management of one or more mobile medical devices, control notifications or messages to various users associated with a specific patient or patient group within connected systems, organize or schedule physician or patient contacts or treatments, or prevent or reduce patient hospitalizations. Proper identification and safe management of the risk of patient deterioration can avoid unnecessary medical interventions, extend the lifespan of mobile medical devices, and reduce healthcare costs. Summary of the Invention

[0006] Systems and methods for detecting conduction-induced premature atrial contractions (PACs) are disclosed. Generally, PACs can be a predictor of atrial fibrillation (AF), stroke, and mortality. Based on the detection of conduction-induced PACs, device-determined PAC load values ​​can be provided to users or processes.

[0007] Example 1 includes a subject (such as an ambulatory medical device (AMD)) comprising cardiac signal sensing circuitry configured to sense cardiac signals representing a patient's cardiac activity when connected to electrodes, and control circuitry. The control circuitry is configured to: monitor cardiac depolarization in the sensed cardiac signals; detect a biphasic distribution of the patient's heart rate; identify cardiac depolarization intervals shorter than a predetermined interval threshold; identify atrial premature contractions (PACs) of normal and abnormal conduction in the sensed cardiac signals; and count the number of conducted PACs and generate an alarm based on that count related to the patient's PAC load.

[0008] In Example 2, the subject of Example 1 may optionally include control circuitry configured to identify PAC by recognizing an ectopic P wave preceding the conducted R wave in the sensed cardiac signal.

[0009] In Example 3, the subject of Example 2 may optionally include control circuitry configured to calculate the correlation between QRS complexes in the sensed cardiac signal and use the correlation to identify PACs in the sensed cardiac signal.

[0010] In Example 4, the subject of Example 2 may optionally include control circuitry configured to analyze ectopic P-wave information and morphology of the sensed cardiac signal to distinguish PAC from premature ventricular contractions (PVC).

[0011] In Example 5, the subject matter of one or any combination of Examples 1-4 may optionally include control circuitry configured to analyze the morphology of the sensed cardiac signals to identify normally conducted PACs and abnormally conducted PACs.

[0012] In Example 6, the subject matter of one or any combination of Examples 1-5 may optionally include control circuitry configured to generate a histogram of the patient’s depolarization interval and determine when the histogram is bimodal.

[0013] In Example 7, the subject matter of one or any combination of Examples 1-6 may optionally include control circuitry configured to: monitor the patient's depolarization interval, generate a histogram of the depolarization interval, detect when the histogram is bimodal, and enable recognition of PAC during a predetermined timing window of the sensed cardiac signal.

[0014] In Example 8, the subject matter of Example 7 may optionally include: communication circuitry configured to wirelessly transmit information to a separate device; and control circuitry configured to: transmit an alarm to the separate device when it is determined that the histogram is bimodal during a multi-day monitoring depolarization interval; and receive commands from the separate device to enable identification of the PAC in response to the commands received from the separate device.

[0015] In Example 9, the subject matter of one or any combination of Examples 1-7 may optionally include: a communication circuit operatively configured to wirelessly transmit information to a separate device; and a control circuit configured to generate a value of the conducted PAC load and include the value of the conducted PAC load in an alarm related to the patient's PAC load.

[0016] Example 10 includes topics (such as methods of operating AMD) or may optionally be combined with one or any combination of Examples 1-9 to include topics such as: monitoring cardiac depolarization in a patient in a sensed cardiac signal sensed using AMD, detecting a biphasic distribution of the patient's heart rate, identifying cardiac depolarization intervals shorter than a predetermined interval threshold, identifying atrial premature contractions (PACs) of normal and abnormal conduction in the sensed cardiac signal, determining the number of conducted PACs, and generating an alarm related to the patient's PAC load based on the number.

[0017] In Example 11, the subject of Example 10 may optionally include AMD detection of ectopic P waves preceding the conducted R waves in the sensed cardiac signal.

[0018] In Example 12, the subject of Example 11 may optionally include AMD using ectopic P wave information and morphology of sensed cardiac signals to distinguish PAC from ventricular premature contractions (PVC).

[0019] In Example 13, the subject matter of one or any combination of Examples 10-12 may optionally include AMD using analysis of the morphology of the sensed depolarization signal to determine when the identified PAC is conducting normally and when it is conducting abnormally.

[0020] In Example 14, the subject matter of one or any combination of Examples 10-13 may optionally include AMD using analysis of the morphology of the sensed depolarization signal to determine when the identified PAC is conducting normally and when it is conducting abnormally.

[0021] In Example 15, the subject matter of one or any combination of Examples 10-14 may optionally include: monitoring the patient's depolarization interval, generating a histogram of the depolarization interval, determining that the histogram is bimodal, and enabling sensing of the depolarization signal in response to determining that the histogram is bimodal, and enabling identification of the conducted PAC during a predetermined timing window of the sensed depolarization signal.

[0022] In Example 16, the subject matter of Example 15 may optionally include: sending an alarm to a separate device when it is determined that the histogram is bimodal; and enabling sensing of the depolarization signal and identification of the conducted PAC in response to a command received from the separate device.

[0023] In Example 17, the subject matter of one or any combination of Examples 10-16 may optionally include AMD using the determined number of conducted PACs to calculate the value of the PAC load.

[0024] Example 18 includes a subject (such as a cardiac rhythm management (CRM) system) or may optionally be combined with one or any combination of Examples 1-17 to include such a subject, including an implantable AMD and an external device. The external device includes communication circuitry configured to wirelessly transmit information to the AMD when it is implanted. The AMD includes: cardiac signal sensing circuitry configured to sense cardiac signals representing the patient's cardiac activity when connected to electrodes; communication circuitry configured to wirelessly transmit information to a separate device; and control circuitry. The control circuitry is configured to: monitor cardiac depolarization in the sensed cardiac signals; detect a biphasic distribution of the patient's heart rate; identify a cardiac depolarization interval shorter than a predetermined interval threshold in response to the detection of a biphasic heart rate; identify conducted R waves in the sensed cardiac signals and detect ectopic P waves preceding the conducted R waves; count the number of conducted ectopic P waves; and generate an alarm related to the patient's PAC load based on the number of conducted ectopic P waves and transmit the alarm to the external device.

[0025] In Example 19, the subject of Example 18 may optionally include: an external device is configured to retrieve information stored in AMD's memory, receive alarms related to PAC load from the retrieved information, and display the alarms related to PAC load to the user of the external device.

[0026] In Example 20, one or both of the subjects in Examples 18 and 19 may optionally include: the AMD includes treatment circuitry for providing electrical pacing therapy to the patient when coupled to an electrode; and the external device is an AMD programmer configured to transmit commands to the AMD to change the treatment mode in response to receiving an alarm related to PAC load.

[0027] These examples can be combined in any arrangement or combination. The content of this invention is intended to provide an overview of the subject matter of this patent application. It is not intended to provide an exclusive or exhaustive interpretation of this disclosure. Detailed description is included to provide further information regarding this patent application. Other aspects of this disclosure will be apparent to those skilled in the art upon reading and understanding the following detailed description and viewing the accompanying drawings, which form a part thereof, and each of the drawings should not be considered limiting. Attached Figure Description

[0028] In drawings that are not necessarily drawn to scale, the same reference numerals may describe similar parts in different views. Similar numbers with different letter suffixes may indicate different instances of similar parts. The drawings illustrate, by way of example and not limitation, the various embodiments discussed in this document.

[0029] Figure 1 An example of a patient management system is shown.

[0030] Figure 2 An example of a mobile medical device (IMD) electrically coupled to the heart is shown.

[0031] Figure 3 This is a block diagram of AMD's electronic circuitry.

[0032] Figure 4 This is a block diagram of an external device that transmits information to AMD.

[0033] Figures 5-7 This is an illustration of an example of a bar chart recording of cardiac depolarization.

[0034] Figure 8 This is a flowchart of the method for operating a CRM system.

[0035] Figure 9 This is a histogram of heart rate. Detailed Implementation

[0036] Mobile medical devices may include or be configured to receive physiological information from one or more sensors located inside, on, or near a patient's body. Among other things, the patient's physiological information may include respiratory information (e.g., respiratory rate, respiratory volume (tidal volume), cardiac acceleration information (e.g., cardiac vibration information, pressure waveform information, heart sound information, endocardial acceleration information, acceleration information, activity information, posture information, etc.); impedance information; cardiac electrical information; body activity information (e.g., activity, steps, etc.); posture or position information; pressure information; plethysmography information; chemical information; temperature information; or other physiological information of the patient.

[0037] The sinoatrial node, located in the atria, typically initiates cardiac contractions in patients via regularly occurring sinus pulses that induce atrial depolarization. Premature atrial contractions (PACs) occur when an ectopic lesion in the atrium discharges before the sinus pulse to initiate atrial depolarization. Generally, PACs can be a predictor of atrial fibrillation (AF), stroke, and mortality. Among other things, the inventors have recognized that systems and methods for estimating PAC burden can be useful for physicians in monitoring the health of patients with heart failure.

[0038] Figure 1 A portion of an example of a Cardiac Rhythm Management (CRM) system 100 and a portion of an environment in which the CRM system 100 can be used are shown. The CRM system 100 may include an implantable AMD 102, an external system 104, and communication links such as a telemetry link 106. The AMD 102 may include an electronic unit coupled to the heart 110 of a subject 112 via a cardiac lead 108 or an additional lead. Examples of the AMD 102 may include, but are not limited to, pacemakers, pacemaker / defibrillators, cardiac resynchronization devices, cardiac remodeling control devices, and insertable cardiac monitors (ICMs). In one example, the AMD 102 may be configured to monitor the health of the heart 110 and identify one or more abnormalities associated with the heart 110. The AMD 102 may take necessary actions, such as stimulating one or more portions of the heart 110 via the lead 108, to treat one or more abnormalities.

[0039] In one example, external system 104 may include external device 107 configured to communicate bidirectionally with AMD 102, such as via telemetry link 106. For example, external device 107 may include a programmer to program AMD 102 to deliver one or more treatments to heart 110. In one 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 delivering cardiac resynchronization therapy (CRT) to heart 110.

[0040] In one example, external device 107 may be configured to transmit data to AMD 102 via telemetry link 106. Examples of such transmitted data may include programmed instructions for AMD 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 one example, AMD 102 may 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 AMD 102, treatment history data, operating status of AMD 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.

[0041] In one example, external device 107 may be part of CRM system 100, which may include other devices such as remote system 114 for remotely programming AMD 102. In one example, remote system 114 may be configured to include server 116, which can communicate with external device 107 via telecommunications network 118, such as accessing AMD 102 to remotely monitor the health of heart 110 or adjust parameters associated with one or more treatments.

[0042] Figure 2 The AMD 102 is illustrated as an implantable medical device (IMD). The AMD 102 is electrically coupled to a heart 110, for example, via one or more leads, which are coupled to the AMD 102 through one or more lead ports (e.g., first, second, or third lead ports 241, 242, 243 in the head 202 of the AMD 102). In one example, the AMD 102 may include an antenna, such as one in the head 202, configured to enable communication with one or more electronic circuits in an external system and a hermetically sealed enclosure (CAN) 201. The AMD 102 illustrates an example medical device (or medical device system) as described herein.

[0043] The AMD 102 may include an implantable medical device (IMD), such as an implantable cardiac monitor (ICM), pacemaker, defibrillator, cardiac resynchronizer, or other subcutaneous IMD or cardiac rhythm management (CRM) device configured for implantation in the chest of a subject, having one or more leads to position one or more electrodes or other sensors at various locations in or near the heart 110, such as one or more locations in the atrium or ventricle. Separately to or in addition to the one or more electrodes or other sensors on the leads, the AMD 102 may include one or more electrodes or other sensors (e.g., pressure sensors, accelerometers, gyroscopes, microphones, etc.) powered by a power source within the AMD 102. The one or more electrodes or other sensors on the leads, the AMD 102, or a combination thereof may be configured to detect physiological information from the patient or to provide one or more treatments or stimulations to the patient.

[0044] AMD 102 may include one or more electronic circuits configured to sense one or more physiological signals, such as electrograms or signals representing the mechanical function of the heart 110. In some examples, CAN 201 may be used as an electrode, such as for sensing or pulse delivery. For example, electrodes from one or more leads may be used with CAN 201, for example, for unipolar sensing of an electrogram or for delivering one or more pacing pulses. Defibrillation electrodes (e.g., first defibrillation coil electrode 228, second defibrillation coil electrode 229, etc.) may be used with CAN 201 to deliver one or more cardioversion / defibrillation pulses.

[0045] In one example, the AMD 102 can sense impedance between electrodes, such as those located on leads or one or more of the CAN 201. The AMD 102 can be configured to inject current between a pair of electrodes, sense a combined voltage between the same or different electrode pairs, and determine impedance, for example, using Ohm's law. Impedance can be sensed in bipolar, tripolar, or quadpolar configurations, in which the same pair of electrodes can be used for both current injection and voltage sensing; in a tripolar configuration, the electrode pair used for current injection and the electrode pair used for voltage sensing can share a common electrode; and in a quadpolar configuration, the electrode used for current injection can be different from the electrode used for voltage sensing. In one example, the AMD 102 can be configured to inject current between electrodes on one or more of the first, second, third, or fourth leads 220, 225, 230, 235 and the CAN 201, and sense a combined voltage between the same or different electrodes and the CAN 201.

[0046] Figure 2Exemplary lead configurations include first, second, and third leads 220, 225, and 230 in conventional lead placements in the coronary veins 216 (e.g., coronary sinuses) above the right atrium (RA) 206, the right ventricle (RV) 207, and the left atrium (LA) 208 and left ventricle (LV) 209, respectively; and a fourth lead 235 positioned in the RV 207 near the His bundle 211, between the AV node 210 and the left and right bundle branches 212, 213 and Purkinje fibers 214, 215. Each lead can be configured to position one or more electrodes or other sensors at various locations in or near the heart 110 to detect physiological information or provide one or more treatments or stimulations.

[0047] The first lead 220, located in RA 206, includes a first tip electrode 221 located at or near the distal end of the first lead 220 and a first ring electrode 222 located near the first tip electrode 221. The second lead 225 (dashed line), located in RV 207, includes a second tip electrode 226 located at or near the distal end of the second lead 225 and a second ring electrode 227 located near the second tip electrode 226. The third lead 230, located in the coronary vein 216 above LV 209, includes a third tip electrode 231 located at or near the distal end of the third lead 230, a third ring electrode 232 located near the third tip electrode 231, and two additional electrodes 233 and 234. The fourth lead 235, located in RV 207 near His bundle 211, includes a fourth tip electrode 236 located at or near the distal end of the fourth lead 235 and a fourth ring electrode 237 located near the fourth tip electrode 236. Tip electrodes and loop electrodes may include pacing / sensing electrodes configured to sense electrical activity or provide pacing stimulation.

[0048] In addition to the tip electrode and the loop electrode, one or more leads may include one or more defibrillation coil electrodes configured to sense electrical activity or provide cardioversion or defibrillation shock energy. For example, the second lead 225 includes a first defibrillation coil electrode 228 located near the distal end of the second lead 225 in RV 207 and a second defibrillation coil electrode 229 located at a distance from the distal end of the second lead 225, such as for placement in or near the superior vena cava (SVC) 217.

[0049] Different CRM devices include varying numbers of leads and lead placements. For example, some CRM devices are single-lead devices with one lead (e.g., RV only, RA only, etc.). Other CRM devices are multi-lead devices with two or more leads (e.g., RA and RV; RV and LV; RA, RV and LV; etc.). CRM devices suitable for His bundle pacing typically use lead ports designated for the LV or RV lead to deliver stimulation to the His bundle 211.

[0050] Figure 3 This is a block diagram of a portion of the electronic circuitry of the implantable AMD 102. The AMD 102 can be coupled to multiple implantable electrodes, such as... Figure 2 The electrode arrangement is described in the example. The AMD 102 includes cardiac signal sensing circuitry 304, treatment circuitry 306, communication circuitry 312, and control circuitry 308. When pacing electrodes are operatively connected to the system, treatment circuitry 306 provides electrical pacing stimulation energy to the patient's heart. The pacing electrodes may include... Figure 2 Any pacing electrode, such as electrodes configured to be placed in or near the RA, RV, LV, His bundle or left bundle branch, and the electrodes of CAN 201.

[0051] The cardiac signal sensing circuit 304 includes one or more sensing amplifiers to sense one or both of a voltage signal or a current signal at the sensing electrodes. The cardiac signal sensing circuit 304 can be used to sense a patient's cardiac electrical information. Timing measures between different features (e.g., first and second cardiac features, etc.) in the sensed electrical signal can be determined, for example, by signal processing circuitry 310 of control circuitry 308. In some examples, the timing measure may include the interval or measure between a first cardiac feature and a second cardiac feature in a patient's first cardiac interval (e.g., the duration of the cardiac cycle or interval, QRS width, etc.) or between first cardiac features and second cardiac features in corresponding consecutive first and second cardiac intervals of the patient. In one example, the first and second cardiac features include equivalent detected features in consecutive first and second cardiac intervals, such as consecutive R waves (e.g., RR interval, etc.) or one or more other features of the cardiac electrical signal. Far-field cardiac signals can be sensed using the electrodes of the CAN. In some examples, the AMD 102 is a diagnostic-only device and does not include treatment circuitry 306.

[0052] Control circuitry 308 may include a digital signal processor, application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), microprocessor, or other type of processor that interprets or executes instructions in software or firmware. In some examples, control circuitry 308 may include a state machine or sequencer implemented in hardware circuitry. Control circuitry 308 may include any combination of hardware, firmware, or software. Control circuitry 308 includes electronic circuitry (e.g., signal processing circuitry 310) to perform the functions described herein. Circuitry may include software, hardware, firmware, or any combination thereof. For example, circuitry may include instructions in software that executes on control circuitry 308. Multiple functions may be performed by one or more circuits of control circuitry 308.

[0053] The control circuit 308 uses the communication circuit 312 to wirelessly transmit information with individual devices. Figure 4 It is used with Figure 3 External devices 107 that communicate with the AMD 102 (e.g., Figure 1 This is a block diagram of an example portion of an external device 107 of a CRM system 100. External device 107 may be a programming device for an AMD 102. The programming device includes a storage device 418, programming control circuitry 416, a user interface 420, and communication circuitry 422. Programming control circuitry 416 may be implemented using an application-specific integrated circuit (ASIC) configured to perform one or more functions or general-purpose circuitry programmed to perform those functions. Among other things, general-purpose circuitry may include a microprocessor or a portion thereof, a microcontroller or a portion thereof, and programmable logic circuitry or a portion thereof. Storage device 418 may be a memory integrated with programming control circuitry 416 or a separate memory device. Communication circuitry 422 wirelessly transmits information to the AMD 102 using near-field inductive wireless signals or far-field radio frequency signals. The programming device can be used to program pacing therapy parameters and other information in the AMD 102.

[0054] Some heart failure patients experience PAC (percutaneous angina). Because PAC can be a predictor of AF, stroke, and mortality, knowing the number or percentage of P waves in a heart failure patient with PAC (PAC burden) can be useful for physicians in determining the effectiveness of drug titration or other treatments.

[0055] Figure 5This is an illustration of an example of a bar chart recording of cardiac depolarization. Depolarization 530 shows the P wave, Q wave, R wave, S wave, and T wave in the PQRST complex of depolarization 530. The depolarized P wave is a normal P wave representing the contraction of the atria in response to an impulse from the sinoatrial node. Figure 5 Two PACs were also shown. The PACs occurred earlier than the normal P waves compared to the previous QRS complex. Figure 5 In the example, the PAC is conducted to the ventricle through the atrioventricular (AV) node 210. The R wave generated by the PAC is labeled R'.

[0056] Figure 6 This is another example of a bar chart recording of cardiac depolarization. Figure 6 The example shows two PACs: a normal P wave and one that is blocked and does not conduct through AV node 210. PACs can be normally conducting, non-conducting, or blocked, as well as anomalously or abnormally conducting.

[0057] Figure 7 This is another example of a bar chart recording of cardiac depolarization. Figure 7 The example illustrates two normal P waves leading to an R wave labeled (R) and an abnormally conducted PAC leading to an R wave labeled (R'). The R wave labeled (R') has a different morphology because an abnormally conducted PAC may conduct to the ventricle via an abnormal path, causing ventricular contractions to differ from normal. As explained earlier in this article, understanding PAC load can be useful for physicians. When estimating PAC load, it is helpful to include only those PACs that conduct (normally or abnormally).

[0058] Figure 8 Is operating AMD 102 (such as Figure 2 and Figure 3 The flowchart of an example of the AMD 102 is shown below. The control circuitry 308 of the AMD 102 executes an algorithm to detect PACs conducting to the ventricles. Conducted PACs can be included in the real-time estimate of the patient's PAC load. PACs included in the estimate of conducted PAC load can be normally conducted (e.g., via atrioventricular (AV) node 210) or abnormally conducted (e.g., via a conduction path different from AV node 210). Blocked PACs that do not conduct to the ventricles are not included in the estimate of conducted PAC load.

[0059] At box 805, the AMD 102 is used to monitor the patient's cardiac depolarization. For example, control circuitry 308 can monitor the intervals between R waves in the cardiac signal sensed by cardiac signal sensing circuitry 304. At box 810, control circuitry 308 detects that the patient's heart rate is bimodal. One method for detecting bimodal heart rate is for control circuitry 308 to generate a histogram of the heart rate and use the histogram to detect bimodal heart rate.

[0060] Figure 9 This is a histogram illustration where the monitored heart rate is binned according to beats per minute (bpm). Alternatively, the histogram can use the interval between heartbeats (the reciprocal of the heart rate), and the bins can be millivolts. Figure 9 In the example, the histogram distribution is bimodal, with one peak approaching 50 beats per minute (50 bpm) and the other peak approaching 100 bpm. The histogram of a patient without PAC will have a more normal distribution. Control circuitry 308 can detect bimodal heart rate by identifying the bin with the largest number of heartbeats, identifying a second bin with a large number of heartbeats, and detecting the troughs of other bins between the first and second bins. For example, in Figure 9 In the example, control circuit 308 will detect a valley of 80 bpm between the 50 bpm and 100 bpm valleys, and can set a logic flag for biphasic heart rate when a valley is detected.

[0061] Return to Figure 8 When control circuit 308 detects a biphasic heart rate, it analyzes the sensed cardiac signal to look for fast beats. In some examples, a window (e.g., a two-minute window) of the sensed cardiac signal is stored during heart rate monitoring, and this stored signal is analyzed by control circuit 308. At block 815, control circuit 308 identifies cardiac depolarization intervals shorter than a predetermined interval threshold as fast beats or short coupling intervals. In some examples, control circuit 308 uses peak detection to identify R waves in the sensed cardiac signal and identifies fast R-wave to R-wave intervals as short coupling intervals. These short coupling intervals are analyzed as potential PAC beats.

[0062] At box 820, control circuitry 308 identifies PACs in short coupling intervals. Control circuitry 308 may use morphological analysis to identify PACs in the sensed cardiac signal. In some examples, control circuitry 308 compares the morphology of a potential PAC to a PAC template stored in the AMD. In some examples, control circuitry 308 determines a score that correlates the morphology of the sensed cardiac signal with the morphology of the template signal representing the PAC. An example of a correlation score is the feature correlation coefficient (FCC). The FCC can provide an indication of the similarity between the shape of the sensed electrogram and the shape of the template electrogram signal representing the PAC. The template may be recorded for a specific subject or may be created based on a patient population. Methods for calculating correlation scores can be found in U.S. Patent No. 7,904,142, filed May 16, 2007, entitled “Self-Adjusting ECG Morphological Feature Correlation Threshold,” the entire contents of which are incorporated herein by reference. When the determined score meets the specified PAC detection threshold score, the arrhythmia detection circuit 620 can detect PAC. The detection of AF can be adjusted by changing the threshold score to make it more or less sensitive.

[0063] like Figure 5 As shown in the example, a PAC can be an ectopic P wave that occurs before the conducted R wave. An ectopic P wave has a different shape than a normal P wave and is closer to the preceding T wave. This difference in signal morphology can be used to identify ectopic P waves. In some examples, control circuit 308 calculates the correlation between a short-interval potential ectopic P wave and a P wave belonging to a longer interval. If the shape of the potential ectopic P wave correlates well with the shapes of other P waves, it is not identified as an ectopic P wave. If the potential ectopic P wave does not correlate well with other P waves, it can be identified as an ectopic P wave. A fast-beating ectopic P wave that occurs before the conducted R wave is identified as a conducted PAC and is included in the estimation of the PAC load. Figure 6 As shown in the example, the P-wave that occurs in the absence of a conducted R-wave is a blocked P-wave, and the control circuit 308 may exclude the blocked P-wave when estimating the PAC load.

[0064] The identified ectopic P-wave can be either normally conducted or abnormally conducted PAC. In some examples, the control circuit executes a fast-pulsating QRS complex morphology to identify abnormally conducted PAC. For example... Figure 7As shown, the morphology of the QRS complex from anomalously conducted PAC differs from that from a normally conducted PAC. In some examples, control circuit 308 calculates the correlation score between the QRS complex and a template QRS complex of a normal sinus rhythm. If the shape of the QRS complex correlates well with the template QRS, it is identified as a normally conducted PAC. If the shape of the QRS complex does not correlate well with the template QRS, it can be identified as an anomalously conducted PAC. Control circuit 308 can maintain separate counting of normally conducted and anomalously conducted PACs.

[0065] In some examples, control circuit 308 distinguishes between PAC and ventricular premature contractions (PVC). Due to PVC, a rapid R-wave to R-wave interval may be detected. However, a rapid R-wave interval caused by PVC does not include a P wave. Control circuit 308 can identify that the rapid R-wave interval is due to PVC rather than PAC by sensing the amplitude of the signal. In some examples, control circuitry uses P-wave information to differentiate between PAC and PVC. PVC is not included in the estimation of PAC load.

[0066] return Figure 8 At block 825, control circuitry 308 maintains a count of the number of identified conducted PACs to estimate the conducted PAC load. When the count of conducted PACs exceeds a predetermined threshold count, or when the count exceeds the threshold count within a predetermined time period, control circuitry 308 generates an alarm related to the patient's PAC load. The PAC load alarm can be a signal transmitted from AMD 102 to external device 107. In some variations, the alarm is a flag stored in memory. External device 107 can receive the alarm when it retrieves information stored in AMD 102. The alarm can be displayed by the user interface of the external device, or the external device can be a server and the alarm can be displayed by the user interface of a third device. In some examples, the alarm includes a value for the conducted PAC load. Some examples of this value include the percentage of heartbeats with PACs, the number of conducted PACs over a period of time, and the number of normally conducted PACs and the number of abnormally conducted PACs.

[0067] Due to the alarm, the physician may change the titration of drug treatment or switch to another treatment. In some examples, control circuitry 308 can modify device-based treatment based on an estimate of conducted PAC load. For example, control circuitry 308 can initiate the delivery of antiarrhythmic therapy to treat or prevent arrhythmia. In some examples, treatment circuitry 306 delivers electrical pacing therapy to the subject. Control circuitry 308 can initiate the delivery of electrical pacing therapy based on a first pacing therapy mode and change the pacing therapy mode based on an estimate of conducted PAC load to prevent arrhythmia. In some examples, external device 107 changes the treatment mode based on a PAC load alarm (e.g., by programming AMD 102).

[0068] In some examples, it is enabled based on long-term monitoring of the patient's heart rate. Figure 8 Method 800. Control circuitry 308 can monitor heart rate over a longer period (e.g., 1-2 weeks) before checking for a biphasic heart rate distribution. If a biphasic heart rate is detected during the extended period, control circuitry 308 then enables the PAC load estimation feature. This can reduce consumption on the AMD 102 power source (e.g., battery) from the PAC load estimation feature. In some examples, AMD 102 control circuitry 308 sends an alert to external device 107 that the histogram is biphasic without enabling the PAC load estimation feature. Control circuitry 308 can enable sensing of depolarization signals and identification of conducted PAC in response to commands received from external device 107.

[0069] Various embodiments are illustrated in the accompanying drawings above. One or more features from one or more of these embodiments can be combined to form other embodiments. The method examples described herein can 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 or system to perform the methods described in the examples above. Implementations of such methods may include code, such as microcode, assembly language code, high-level language code, etc. Such code may include computer-readable instructions for performing various methods. The code may form part of a computer program product. Furthermore, the code may be tangibly stored on one or more volatile or non-volatile computer-readable media during execution or at other times.

[0070] The detailed description above is intended to be illustrative and not restrictive. Therefore, the scope of this disclosure should be determined by referring to the appended claims and the full scope of their equivalents.

Claims

1. A mobile medical device (AMD), the device comprising: A cardiac signal sensing circuit, configured to sense cardiac signals representing a patient’s cardiac activity when connected to electrodes; The control circuit is configured as follows: Monitor cardiac depolarization in the sensed cardiac signals; The bimodal distribution of the patient's heart rate was detected; Identify cardiac depolarization intervals shorter than a predetermined interval threshold; Identify atrial premature contractions (PACs) with normal and abnormal conduction in the sensed cardiac signals; and The number of conducted PACs is counted, and an alarm related to the patient's PAC load is generated based on the count.

2. The device according to claim 1, wherein, The control circuit is configured to identify the PAC by recognizing an ectopic P wave preceding the conducted R wave in the sensed cardiac signal.

3. The device according to claim 2, wherein, The control circuit is configured as follows: Calculate the correlation between QRS complexes in the sensed cardiac signals; and The correlation is used to identify the PAC in the sensed cardiac signal.

4. The device according to claim 2 or claim 3, wherein, The control circuit is configured to analyze the ectopic P wave information and morphology of the sensed cardiac signal to distinguish the PAC from ventricular premature contractions (PVCs).

5. The device according to any one of claims 1-4, wherein, The control circuit is configured to analyze the morphology of the sensed cardiac signal to identify normally conducted PACs and abnormally conducted PACs.

6. The device according to any one of claims 1-5, wherein, The control circuit is configured to generate a histogram of the patient's depolarization interval and determine when the histogram is bimodal.

7. The device according to any one of claims 1-6, wherein, The control circuit is configured as follows: Monitor the depolarization interval of the patients; Generate a histogram of the depolarization interval; Detecting when the histogram is bimodal; and Identification of the PAC is enabled during a predetermined timing window of the sensed cardiac signal.

8. The device according to claim 7, comprising: A communication circuit, which is operatively coupled to the control circuit and configured to wirelessly transmit information to a separate device; The control circuit is configured as follows: Monitoring the depolarization interval over multiple days; When it is determined that the histogram is bimodal, an alarm is sent to the individual device; and Receive a command from the separate device to enable identification of the PAC in response to the command received from the separate device.

9. The device according to any one of claims 1-8, comprising: A communication circuit, which is operatively coupled to the control circuit and configured to wirelessly transmit information to a separate device; and The control circuit is configured to generate a value of the conducted PAC load and include the value of the conducted PAC load in the alarm related to the patient's PAC load.

10. A method of operating a mobile medical device (AMD), the method comprising: Monitor cardiac depolarization in patients using sensed cardiac signals sensed using AMD; The bimodal distribution of the patient's heart rate was detected; Identify cardiac depolarization intervals shorter than a predetermined interval threshold; Identify atrial premature contractions (PACs) with normal and abnormal conduction in the sensed cardiac signals; and The number of conducted PACs is determined, and an alarm related to the patient's PAC load is generated based on the number.

11. The method according to claim 10, wherein, Identifying PAC includes the AMD detecting ectopic P waves preceding the conducted R wave in the sensed cardiac signal.

12. The method of claim 11, wherein the AMD uses ectopic P wave information and morphology of the sensed cardiac signal to distinguish PAC from ventricular premature contractions (PVC).

13. The method according to any one of claims 10-12, comprising the AMD using analysis of the morphology of the sensed depolarization signal to determine when the identified PAC is conducting normally and when it is conducting abnormally.

14. The method according to any one of claims 10-13, wherein, Detecting a bimodal distribution of heart rate involves generating a histogram of the patient's depolarization interval and determining that the histogram is bimodal.

15. The method according to any one of claims 10-14, wherein, The bimodal distribution of heart rate detection includes: Monitor the depolarization interval of the patients; Generate a histogram of the depolarization interval; Determine that the histogram is bimodal; and In response to determining that the histogram is bimodal, sensing of the depolarization signal is enabled, and identification of the conducted PAC is enabled during a predetermined timing window of the sensed depolarization signal.

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