SYNCHRONIZING RATE RESPONSES BETWEEN TWO CARDIAC PACEMAKERS

A computing device may be communicably coupled to a first pacemaker implanted in a heart of a patient and a second pacemaker implanted in the heart of the patient. The computing device may receive, from the first pacemaker, first race responsive pacing data, and may receive, from the second pacemaker, second rate responsive pacing data. The computing device may synchronize, based at least in part on the first rate responsive pacing data and the second rate responsive pacing data, rate responsive pacing of the first pacemaker and the second pacemaker.

TECHNICAL FIELD

This disclosure generally relates to medical devices and, more particularly, synchronizing rate responses between two rate responsive cardiac pacemakers.

BACKGROUND

A rate responsive cardiac pacemaker may perform rate responsive cardiac pacing for a patient by changing its cardiac pacing rate based on changes in the activity level of the patient. In some instances, two or more rate responsive cardiac pacemakers may be implanted in the patient to each perform rate responsive cardiac pacing for the patient, e.g., for respective chambers of the heart of the patient, based on the activity level of the patient detected by each of the two or more rate responsive cardiac pacemakers.

SUMMARY

In accordance with the techniques of the disclosure, a medical device system is set forth herein that is able to accurately and seamlessly synchronize the pacing rate of two or more pacemakers that perform rate responsive cardiac pacing for a patient regardless of changes in the activity level of the patient. A computing device, such as a programmer, an external monitor, or a mobile device may receive rate responsive pacing data from each of the two or more pacemakers and may synchronize, based on the rate responsive pacing data from each of the two or more pacemakers, the rate responsive cardiac pacing of each of the two or more pacemakers. The techniques of this disclosure therefore enables multiple rate responsive pacemakers in a patient to perform cardiac pacing at the same pacing rate, thereby improving the comfort of the patient and reducing any potential negative medical outcomes from multiple pacemakers in the patient performing cardiac pacing at different rates.

In some aspects, the techniques described herein relate to a method including: receiving, by processing circuitry from a first pacemaker implanted in a heart of a patient, first rate responsive pacing data; receiving, by the processing circuitry from a second pacemaker implanted in the heart of the patient, second rate responsive pacing data; and synchronizing, by the processing circuitry and based at least in part on the first rate responsive pacing data and the second rate responsive pacing data, rate responsive pacing of the first pacemaker and the second pacemaker.

In some aspects, the techniques described herein relate to a medical device including: memory; and processing circuitry operably coupled to the memory and configured to: receive, from a first pacemaker implanted in a heart of a patient, first rate responsive pacing data; receive, from a second pacemaker implanted in the heart of the patient, second rate responsive pacing data; and synchronize, based at least in part on the first rate responsive pacing data and the second rate responsive pacing data, rate responsive pacing of the first pacemaker and the second pacemaker.

In some aspects, the techniques described herein relate to a non-transitory computer-readable medium including instructions that, when executed by processing circuitry of a medical device, cause the medical device to: receive, from a first pacemaker implanted in a heart of a patient, first rate responsive pacing data; receive, from a second pacemaker implanted in the heart of the patient, second rate responsive pacing data; and synchronize, based at least in part on the first rate responsive pacing data and the second rate responsive pacing data, rate responsive pacing of the first pacemaker and the second pacemaker.

This summary is intended to provide an overview of the subject matter described in this disclosure. It is not intended to provide an exclusive or exhaustive explanation of the apparatus and methods described in detail within the accompanying drawings and description below. Further details of one or more examples are set forth in the accompanying drawings and the description below.

DETAILED DESCRIPTION

In general, aspects of this disclosure are directed to a medical device system that synchronizes the pacing rate of two or more pacemakers that perform rate responsive cardiac pacing for a patient regardless of changes in the activity level of the patient. A computing device, such as a programmer, an external monitor, or a mobile device may receive rate responsive pacing data from each of the two or more pacemakers and may synchronize, based on the rate responsive pacing data from each of the two or more pacemakers, the rate responsive cardiac pacing of each of the two or more pacemakers.

The computing device may synchronize, based on the rate responsive pacing data from each of the two or more pacemakers, the rate responsive cardiac pacing of each of the two or more pacemakers. By synchronizing the rate responsive cardiac pacing of each of the two or more pacemakers, the two or more pacemakers may perform cardiac pacing at similar rates as the activity level of the patient changes.

Each of the two or more pacemakers may perform rate responsive cardiac pacing using a respective rate response slope, which is a mapping of the activity level of a patient to the pacing rate of the respective pacemaker that correlates changes to the pacing rate of the respective pacemaker to changes in the activity level of the patient. In some examples, each of the two or more pacemakers may determine the activity level of the patient in the form of an activity count, which is a value that corresponds to the activity level of the patient, and the computing device may synchronize the rate responsive cardiac pacing of each of the two or more pacemakers by synchronizing the activity counts determined by each of the two or more pacemakers. That is, the two or more pacemakers may each, for a particular activity level of the patient, determine the same or similar activity count.

To synchronize the activity counts determined by each of the two or more pacemakers, the patient may undergo a triggered exercise test during which the two or more pacemakers may collect detailed information regarding the patient, such as the rate responsive pacing data. The computing device may thereby use such detailed information to synchronize the rate responsive cardiac pacing of the two or more pacemakers by matching the activity counts between each of the two or more pacemakers.

The techniques of this disclosure therefore enables multiple rate responsive pacemakers in a patient to perform cardiac pacing at the same pacing rate, thereby improving the comfort of the patient and reducing any potential negative medical outcomes from multiple pacemakers in the patient performing cardiac pacing at different rates.

FIG.1illustrates the environment of an example medical device system2in conjunction with a patient4, in accordance with an apparatus and method of certain examples described herein. As shown inFIG.1, medical device system2includes two or more rate responsive cardiac pacemakers, such as pacemaker10A and pacemaker10B, and one or more computing devices, such as computing device12.

Each of pacemakers10A and10B (collectively “pacemakers10”) may be a leadless intracardiac cardiac pacemaker adapted for implantation within heart6of patient4that delivers electrical stimulation pulses to heart6. Each of pacemakers10A and10B may be in wireless communication with computing device12, as illustrated inFIG.1. In some examples, pacemakers10A and10B may be implanted at different locations within heart6. For example, pacemaker10A may be an atrial intracardiac pacemaker implanted in an atrium of heart6(e.g., right atrium or left atrium) and pacemaker10B may be a ventricular intracardiac pacemaker implanted in a ventricle in heart6(e.g., right ventricle or left ventricle).

Pacemakers10A and10B are each capable of producing electrical stimulation pulses, e.g., pacing pulses, delivered to heart6via one or more electrodes on the outer housing of pacemaker10A and pacemaker10B, respectively. Pacemakers10A and10B are rate responsive (also called rate modulated) cardiac pacemakers configured to adapt the pacing rate of pacemakers10A and10B to changes in patient4's physical activity. Each of pacemakers10A and10B may include an activity sensor, such as an accelerometer or other motion sensor that measures patient4's movement, and/or a respiration sensor, and may determine, based on patient4's movement or other activity, the appropriate pacing rate for patient4. As patient4's activity level changes, the activity sensors of pacemakers10A and10B may be able to measure such changes in patient4's activity level, and pacemakers10A and10B may, based on the changes in patient4's activity level, adjust the pacing rate for patient4.

Pacemakers10A and10B may each use a respective rate response slope, which may refer to any function relating activity level to pacing rate, to determine the pacing rate for a corresponding activity level of patient4. A rate response slope for a rate responsive cardiac pacemaker, such as pacemaker10A and pacemaker10B, is a mapping of the activity level of patient4to the pacing rate of the pacemaker that correlates changes to the pacing rate of the pacemaker to changes in the activity level of patient4. When pacemaker10A detects an increase in patient4's activity level, pacemaker10A may use a rate response slope to determine whether and by how much to increase the pacing rate of pacemaker10A. Similarly, when pacemaker10A detects a decrease in patient4's activity level, pacemaker10A may use a rate response slope to determine whether and by how much to decrease the pacing rate of pacemaker10A. In some examples, pacemakers10A and10B may periodically determine an activity level and then determine, based on the rate response slope, whether to change the pacing rate and to what value to change the pacing rate. Pacemakers10A and10B may each be associated with a separate rate response slope.

In some examples, a rate response slope, such as the rate response slope associated with pacemaker10A and/or the rate response slope associated with pacemaker10B, may be associated with a lower rate (LR) that indicates the minimum pacing rate and an upper rate (UR) that indicates the maximum pacing rate. A pacing rate between the LR and the UR on the rate response slope may be an adjusted daily living (ADL) rate, which is a pacing rate associated with a desired rate response during normal daily activities of patient4, such as getting into and out of bed, walking around the house, and the like. The portion of the rate response slope between the UR and the ADL rate may be referred to as the ADL range, and the portion of the rate response slope between the ADL rate and the UR may be referred to as an exertion range. That is, the ADL range may include a range of pacing rates between the LR and the ADL rate, and the exertion range may include a range of pacing rates between the ADL rate and the UR rate. In some examples, the slope of the ADL range of the rate response slope may differ from the slope of the exertion range of the rate response slope, so that the rate response slope may actually include two rate response slopes: a first rate response slope in the ADL range and a second rate response slope in the exertion range.

In some examples, a rate response slope may include a rate response slope for increasing pacing rates and a rate response slope for decreasing pacing rates. When pacemaker10A detects an increase in patient4's activity level, pacemaker10A may use an acceleration rate response slope for increasing pacing rates to determine whether and by how much to increase the pacing rate of pacemaker10A. When pacemaker10A detects a decrease in patient4's activity level, pacemaker10A may use a deceleration rate response slope for decreasing pacing rates to determine whether and by how much to decrease the pacing rate of pacemaker10A.

In some examples, pacemakers10A and10B may each determine the activity level of patient4in the form of an activity count, which is a value that corresponds to the activity level of patient4. Each of pacemakers10A and10B may determine the activity count for patient4based at least in part on the accelerometer signals outputted by the activity sensors of pacemakers10A and10B, such as determining the activity count for patient4based at least in part on the frequency and amplitude of one or more axis of the accelerometer signals outputted by the activity sensors of pacemakers10A and10B.

Computing device12may be a computing device configured for use in settings such as a home, clinic, or hospital, and may further be configured to communicate with pacemaker10via wireless telemetry. For example, computing device12may be coupled to a remote patient monitoring system, such as Carelink®, available from Medtronic Inc., of Minneapolis, Minn. Computing device12may, in some examples, comprise a programmer, an external monitor, or a mobile device, such as a mobile phone, a “smart” phone, a laptop, a tablet computer, a personal digital assistant (PDA), etc. In some examples, computing device12is a wearable electronic device, such as the SEEQ™ Mobile Cardiac Telemetry (MCT) system that was available from Medtronic, Inc., the AVIVO™ Mobile Patient Management (MPM) system that was available from Medtronic, Inc., a Holter monitor, or a type of wearable “smart” electronic apparel, such as a “smart” watch, “smart” patch, or “smart” glasses.

In some examples, a user, such as patient4, a physician, technician, surgeon, electro-physiologist, or other clinician, may interact with computing device12to retrieve physiological or diagnostic information from pacemakers10A and10B. In some examples, a user, such as patient4or a clinician as described above, may also interact with computing device12to program pacemakers10A and10B, e.g., select or adjust values for operational parameters of pacemakers10A and10B. In some examples, computing device12acts as an access point to facilitate communication with pacemakers10A and10B. In some examples, computing device12may continually communicate with pacemakers10A and10B so that pacemakers10A and10B may continually send information sensed by pacemakers10A and10B, such as heart rate data of patient4, cardiac electrogram data of patient4, metrics of delivery of pacing or other therapies to patient4, and the like to computing device12.

Examples of communication techniques used by pacemakers10A and10B and computing device12include radiofrequency (RF) telemetry, which may be an RF link established via Bluetooth, Wi-Fi, or medical implant communication service (MICS). In some examples, computing device12may include a user interface configured to allow patient4, a clinician, or another user to remotely interact with pacemakers10A and10B.

In some such examples, computing device12, and/or any other device of medical device system2, may be a wearable device (e.g., in the form of a necklace or other wearable item), that is operable to track the activity level of patient4. Patient4may wear computing device12on or near patient4's chest, such as via a necklace that hangs computing device12on or near patient4's chest, via a strap that straps computing device12on or near patient4's chest, and the like. Computing device12being worn by patient4so that computing device12is situated on or near patient4's chest may enable computing device12to potentially track the activity level of patient4in ways that may better reflect the actual activity level of patient4compared with devices that may be worn on patient4's periphery, such as on patient4's legs or hands.

Additional examples of the one or more other implanted or computing devices may include an implanted, multi-channel cardiac pacemaker, ICD, IPG, leadless (e.g., intracardiac) pacemaker, extravascular pacemaker and/or ICD, or other IMD or combination of such IMDs configured to deliver CRT to heart6, an external monitor, an external therapy delivery device such as an external pacing or electrical stimulation device, or a drug pump.

In accordance with the techniques of the disclosure, medical device system2may be configured to synchronize the rate response between pacemakers10A and10B, so that pacemakers10A and10B may perform cardiac pacing of heart6at similar rates as the activity level of patient4changes. Specifically, computing device12may communicate with pacemaker10A and/or pacemaker10B to program pacemaker10A and/or pacemaker10B to synchronize the rate response between pacemakers10A and10B to perform cardiac pacing at similar rates.

In some examples, synchronizing the rate response between pacemakers10A and10B may include synchronizing the rate response of pacemaker10A in the ADL range with the rate response of pacemaker10B in the ADL range and synchronizing the rate response of pacemaker10A in the exertion range with the rate response of pacemaker10B in the exertion range. In some examples, synchronizing the rate response between pacemakers10A and10B may include synchronizing the acceleration rate response scope of pacemaker10A with the acceleration rate response scope of pacemaker10B and synchronizing the deceleration rate response scope of pacemaker10A with the deceleration rate response scope of pacemaker10B.

Synchronize the rate response between pacemakers10A and10B, may not necessarily mean that pacemakers10A and10B each performs cardiac pacing of heart6at the same pacing rate at a given activity level of patient4. In some examples, the rate response between pacemakers10A and10B may be synchronized such that, given an activity level of patient4, pacemakers10A and10B may perform cardiac pacing at pacing rates that differ by no more than a specified amount of bpm or that differ by no more than a specified percentage. In some examples, the rate response between pacemakers10A and10B may be synchronized such that, given an activity level of patient4, pacemakers10A and10B may perform cardiac pacing at pacing rates that differ by a fixed amount of bpm.

In some examples, the rate response between pacemakers10A and10B may be synchronized such that, given an activity level of patient4, pacemakers10A and10B may perform cardiac pacing at pacing rates that differ by a first fixed amount of bpm when in the ADL range and that differ by a second fixed amount of bpm different from the first fix amount of bpm when in the exertion range.

In some examples, computing device12may be configured to synchronize the rate response between pacemakers10A and10B by synchronizing the activity counts determined by pacemakers10A and10B. Pacemakers10A and10B may each determine the activity level of patient4in the form of an activity count, which is a value that corresponds to the activity level of patient4. Each of pacemakers10A and10B may determine the activity count for patient4based at least in part on the accelerometer signals outputted by the activity sensors of pacemakers10A and10B, such as determining the activity count for patient4based at least in part on the frequency and amplitude of the accelerometer signals outputted by the activity sensors of pacemakers10A and10B.

Because pacemakers10A and10B are disposed at different locations within heart6of patient4, the activity sensors of pacemakers10A and10B may sense different amounts of movement, such as by sensing different levels of forces in different directions, as patient4moves, and may therefore generate accelerometer signals with different values. As such, when patient4is physically active, pacemakers10A and10B may not necessarily determine, at any point in time, the same activity counts. As such, computing device12may synchronize the rate response between pacemakers10A and10B by synchronizing the activity counts determined by pacemakers10A and10B. In some examples, pacemakers10A and10B may be able to communicate with each other within use of computing device12to synchronize the rate response between pacemakers10A and10B.

To synchronize the activity counts determined by pacemakers10A and10B, patient4may undergo a triggered exercise test that includes at least a period during which patient4performs moderate exercise and at least a period during which patient4is at rest. Such a triggered exercise test may be triggered by a clinician, and computing device14may send, to each of pacemakers10A and10B, an indication that a triggered exercise test is starting when the triggered exercise test begins and an indication that a triggered exercise test is ending when the triggered exercise test ends. During the triggered exercise test, each of pacemakers10A and10B may collect detailed information such as the activity counts, pacing rates, parameters of the activity sensors of pacemakers10A and10B, the accelerometer signals generated by the activity sensors of pacemakers10A and10B, and the like.

Computing device12may be configured to receive from pacemakers10A and10B the detailed information collected by pacemakers10A and10B and to synchronize the rate response between pacemaker10A and pacemaker10B based at least in part on the detailed information collected by pacemakers10A and10B during the triggered exercise test by matching the activity counts between pacemakers10A and10B. That is, given a set of activity counts generated by pacemaker10A during the triggered exercise test and a set of activity counts generated by pacemaker10B during the triggered exercise test, computing device12may be configured to modify the parameters of one or both of the activity sensors and/or the activity count algorithm used by one or both of pacemakers10A and10B to generate the activity counts so that the activity counts generated by pacemaker10A during the triggered exercise test matches (e.g., differs by no more than a threshold value or percentage from) the activity counts generated by pacemaker10B during the triggered exercise test.

In some examples, computing device12may be configured to modify parameters, such as the blanking period, the filter, and the gain of the activity sensor of pacemaker10A, such that the activity sensor of pacemaker10A would generate activity counts from the signals measured by pacemaker10A during the triggered exercise test that match the activity counts generated by pacemaker10B during the triggered exercise test. Computing device12may therefore be configured to program pacemaker10A with the modified parameters of the activity sensor of pacemaker10A and/or the modified activity count algorithm used by pacemaker10A.

In some examples, computing device12may be configured to synchronize the rate response between pacemaker10A and pacemaker10B based at least in part on the detailed information collected by pacemakers10A and10B during the triggered exercise test by matching rate response slopes of pacemakers10A and10B during the triggered exercise test. To match the rate response slopes of pacemakers10A and10B, computing device12may modify the rate response of pacemaker10A and/or pacemaker10B so that the rate response slope of pacemaker10A during the triggered exercise test matches (e.g., is the same as or within a threshold from) the rate response slope of pacemaker10B during the triggered exercise test without modifying the activity counts generated by either pacemaker10A or pacemaker10B.

Pacemaker10A and pacemaker10B may each determine associations between activity counts and pacing rates, so that given an activity count value, a pacemaker may determine an associated pacing rate. Computing device12may therefore be configured to use the rate response slope of pacemaker10B as a reference to modify the pacing rates associated with one or more activity counts for pacemaker10A, thereby modifying the rate response slope of pacemaker10A to match the rate response slope of pacemaker10B. In this way, pacemaker10A may use a rate response slope that matches the rate response slope of pacemaker10B during the triggered exercise test.

In some examples, computing device12may be configured to modify associations between activity counts and pacing rates for pacemaker10A as well as associations between activity counts and pacing rates for pacemaker10B to achieve a specified target pacing rate given a specified activity level. For example, computing device12may be configured to modify the associations between activity counts and pacing rates for pacemaker10A as well as the associations between activity counts and pacing rates for pacemaker10B to achieve a target pacing rate of 100 beats per minute (bpm) when patient4is performing moderate exercise. Computing device12may therefore be configured to modify the associations between activity counts and pacing rates for pacemaker10A to produce, given the activity counts generated by pacemaker10A while patient4is performing moderate exercise, a targeted pacing rate (e.g., 100 bpm). Similarly, computing device12may be configured to modify associations between activity counts and pacing rates for pacemaker10B to produce, given the activity counts generated by pacemaker10B while patient4is performing moderate exercise, a targeted pacing rate (e.g., 100 bpm). Computing device12may therefore be configured to program pacemaker10A and/or pacemaker10B with the modified associations between activity counts and pacing rates.

In some examples, computing device12may be configured to modify the rate response slopes of pacemakers10A and10B to match the sensor rate histograms between pacemakers10A and10B. That is, computing device12may be configured to modify the rate response algorithm of pacemaker10A and/or pacemaker10to generate, for a given time period, the same or similar (e.g., within a specified percentage) distribution of pacing rates by pacemakers10A and10B. A sensor rate histogram for a pacemaker is a graph that illustrates range distributions of the pacing rate of the pacemaker. Computing device12may be configured to, at a follow-up clinical visit by patient4, download or otherwise receive sensor rate data from pacemakers10A and10B. Such sensor rate data may be data sensed and stored by pacemakers10A and10B since the previous follow-up. Computing device12may be configured to collate or otherwise process the sensor rate data from pacemakers10A and10B to determine a sensor rate histogram for pacemaker10A indicative of the distribution of pacing rates by pacemaker10A during the period since the last follow-up clinical visit and a sensor rate histogram for10B indicative of the distribution of pacing rates by pacemaker10bduring the period since the last follow-up clinical visit.

Computing device12may be configured to receive sensor rate data from pacemaker10A and to determine, based on the sensor rate data from pacemaker10A, a sensor rate histogram for pacemaker10A. Similarly, computing device12may be configured to receive sensor rate data from pacemaker10B and to determine, based on the sensor rate data from pacemaker10B, a sensor rate histogram for pacemaker10B. Sensor rate data received from pacemakers10A and10B may be information regarding the pacing rates of each of pacemakers10A and10B over time since the last follow-up clinical visit by patient4, the activity counts associated with the pacing rates of each of pacemakers10A and10B over time since the last follow-up clinical visit by patient4, and the like.

Computing device12may be configured to modify the rate response slope of at least one of pacemaker10A and pacemaker10B so that the sensor rate histogram of pacemaker10A matches (e.g., is the same as) the sensor rate histogram of pacemaker10B. In some examples, computing device12may be configured to modify rate response slope of pacemaker10A by modifying or determining a rate response algorithm for pacemaker10A, such that the rate response algorithm is usable by pacemaker10A to generate, based on the activity counts associated with the pacing rates of pacemakers10A since the last follow-up clinical visit by patient4, associated pacing rates having distribution that matches the distribution of pacing rates of pacemaker10B over time since the last follow-up clinical visit by patient4, which corresponds to the second sensor rate histogram. Computing device12may therefore cause pacemaker10A to use the determined rate response algorithm for determining pacing rates based on activity counts, such as by programming pacemaker10A to use the determined rate response algorithm, sending an indication of the determined rate response slope to pacemaker10A, and the like.

In examples where each of the rate response slopes of pacemakers10A and10B may be in an ADL range and an exertion range, computing device12may be configured to separately modify the rate response slope of pacemaker10A in the ADL range and the portion of the rate response slope of pacemaker10A in the exertion range so that the rate response slope of pacemaker10A in the ADL range matches the rate response slope of pacemaker10B in the ADL range and the rate response slope of pacemaker10A in the exertion range matches the rate response slope of pacemaker10B in the exertion range. For example, computing device12may be configured to modify or determine a first rate response algorithm that is usable by pacemaker10A to generate associated pacing rates in the ADL range having a distribution that matches the distribution of pacing rates in the ADL range of pacemaker10B. Computing device12may also be configured to modify or determine a second rate response algorithm different from the first rate response algorithm that is usable by pacemaker10A to generate associated pacing rates in the exertion range having a distribution that matches the distribution of exertion rates in the ADL range of pacemaker10B.

In some examples, computing device12may be configured to modify the rate response slopes of pacemakers10A and10B to match the activity count histograms between pacemakers10A and10B. That is, computing device12may be configured to modify the rate response algorithm of pacemaker10A and/or pacemaker10to generate, for a given time period, the same or similar (e.g., within a specified percentage) distribution of activity counts by pacemakers10A and10B. An activity count histogram for a pacemaker is a graph that illustrates range distributions of the activity counts of the pacemaker.

Computing device12may be configured to, at a follow-up clinical visit by patient4, download receive, or otherwise determine activity counts from the data produced by pacemakers10A and10B since the previous follow-up. For example, activity counts may be determined based on the accelerometer signals outputted by the activity sensors of pacemakers10A and10B. Computing device12may be configured to collate or otherwise process the activity counts from each of pacemakers10A and10B to determine an activity count histogram for pacemaker10A indicative of the distribution of activity counts determined by pacemaker10A during the period since the last follow-up clinical visit and an activity counts histogram for10B indicative of the distribution of activity counts determined by pacemaker10bduring the period since the last follow-up clinical visit.

Computing device12may be configured to modify the rate response slope of at least one of pacemaker10A and pacemaker10B so that the activity count histogram of pacemaker10A matches (e.g., is the same as or is within a specified percentage of) the activity count histogram of pacemaker10B. In some examples, computing device12may be configured to modify rate response slope of pacemaker10A by modifying or determining a rate response algorithm for pacemaker10A, such that the rate response algorithm is usable by pacemaker10A to generate a distribution of activity counts that matches the distribution of the activity counts of pacemaker10B over time since the last follow-up clinical visit by patient4, which corresponds to the second activity count histogram. Computing device12may therefore cause pacemaker10A to use the determined rate response algorithm for determining pacing rates based on activity counts, such as by programming pacemaker10A to use the determined rate response algorithm, sending an indication of the determined rate response slope to pacemaker10A, and the like.

In examples where each of the rate response slopes of pacemakers10A and10B may be in an ADL range and an exertion range, computing device12may be configured to separately modify the rate response slope of pacemaker10A in the ADL range and the portion of the rate response slope of pacemaker10A in the exertion range so that the rate response slope of pacemaker10A in the ADL range matches the rate response slope of pacemaker10B in the ADL range and the rate response slope of pacemaker10A in the exertion range matches the rate response slope of pacemaker10B in the exertion range. For example, computing device12may be configured to modify or determine a first rate response algorithm that is usable by pacemaker10A to determine pacing rates in the ADL range having a distribution of activity counts that matches the distribution of pacing rates in the ADL range of pacemaker10B. Computing device12may also be configured to modify or determine a second rate response algorithm different from the first rate response algorithm that is usable by pacemaker10A to determine associated pacing rates in the exertion range having a distribution of activity counts that matches the distribution of exertion rates in the ADL range of pacemaker10B. The techniques of the disclosure may provide specific improvements to the field of rate responsive cardiac pacing by cardiac pacemakers such as pacemakers10A and10B. For example, the techniques of the disclosure may ensure that two different pacemakers implanted in a patient perform cardiac pacing at the same rate, thereby potentially improving patient comfort and reducing any potential patient discomfort from mismatches in the cardiac pacing rate of pacemakers implanted in the patient.

FIG.2is a conceptual diagram illustrating an example of a rate responsive pacemaker in accordance with the techniques of the disclosure. As shown inFIG.2, pacemaker10is an example of pacemaker10A and pacemaker10B ofFIG.1. Pacemaker10includes electrodes162and164spaced apart along the housing150of pacemaker10for sensing electrogram data from heart6ofFIG.1and delivering pacing pulses to heart6. Electrode164is shown as a tip electrode extending from a distal end102of pacemaker10, and electrode162is shown as a ring electrode along a mid-portion of housing150, for example adjacent proximal end104. Distal end102is referred to as “distal” in that it is expected to be the leading end as pacemaker10is advanced through a delivery tool, such as a catheter, and placed against a targeted pacing site.

Electrodes162and164form an anode and cathode pair for bipolar cardiac pacing and sensing. In alternative embodiments, pacemaker10may include two or more ring electrodes, two tip electrodes, and/or other types of electrodes exposed along pacemaker housing150for delivering electrical stimulation to heart6and sensing electrogram data. Electrodes162and164may be, without limitation, titanium, platinum, iridium or alloys thereof and may include a low polarizing coating, such as titanium nitride, iridium oxide, ruthenium oxide, platinum black, among others. Electrodes162and164may be positioned at locations along pacemaker10other than the locations shown.

Housing150is formed from a biocompatible material, such as a stainless steel or titanium alloy. In some examples, the housing150may include an insulating coating. Examples of insulating coatings include parylene, urethane, PEEK, or polyimide, among others. The entirety of the housing150may be insulated, but only electrodes162and164uninsulated. In the illustrated example, electrode162may be an uninsulated portion of an electrically conductive part of housing150, and electrode164may be conductive element disposed within an insulative part of housing150. Electrode164may serve as a cathode electrode and be coupled to internal circuitry, e.g., a pacing pulse generation circuit and electrogram sensing circuitry, enclosed by housing150via an electrical feedthrough crossing housing150. Electrode162may be formed to define a ring electrode as generally shown inFIG.2. In other examples, the entire periphery of the housing150may function as an electrode that is electrically isolated from tip electrode164, instead of providing a localized ring electrode such as anode electrode162. Electrode162formed along an electrically conductive portion of housing150serves as a return anode during pacing and sensing.

The housing150includes a control electronics subassembly152, which houses the electronics153for sensing cardiac signals, producing pacing pulses and controlling therapy delivery and other functions of pacemaker10. Pacemaker10may further include an activity sensor, which may be implemented, e.g., as a multi-axial accelerometer enclosed within housing150. The accelerometer provides a signal to a processor included in control electronics subassembly152for signal processing and analysis for generating accelerometer signals that pacemaker10may be configured to use to generate activity counts, and pacemaker10may be configured to use a rate response algorithm to determine, based on the activity counts, pacing rates.

Housing150further includes a battery subassembly160, which provides power to the electronics153. Additional description of batteries implemented by battery subassembly160may be found in U.S. Pat. No. 8,433,409 to Johnson, et al., entitled “Implantable medical device battery,” filed on Jan. 29, 2019, and issued on Apr. 30, 2013 and in U.S. Pat. No. 8,541,131 to Lund, et al., entitled “Elongate battery for implantable medical device,” filed on Aug. 28, 2009, and issued on Sep. 24, 2013, the entire contents of each of which are incorporated herein by reference.

Pacemaker10may include a set of fixation tines166to secure pacemaker10to patient tissue, e.g., by actively engaging with the atrial or ventricular endocardium. Fixation tines166are configured to anchor pacemaker10to position electrode164in operative proximity to a targeted tissue for delivering therapeutic electrical stimulation pulses. Numerous types of active and/or passive fixation members may be employed for anchoring or stabilizing pacemaker10in an implant position. Additional detail with respect to fixation tines166may be found in U.S. Pat. No. 9,775,982 to Grubac, et al., entitled “Implantable medical device fixation,” filed on Apr. 28, 2011 and issued on Oct. 3, 201, the entire content of which is incorporated herein by reference.

Pacemaker10may optionally include a delivery tool interface158. Delivery tool interface158may be located at the proximal end104of pacemaker10and is configured to connect to a delivery device, such as a catheter, used to position pacemaker10at an implant location during an implantation procedure, for example within a heart chamber.

FIG.3is a block diagram illustrating an example configuration of computing device12ofFIG.1. In the example ofFIG.3, the at least one computing device12includes processing circuitry20, communication circuitry26, one or more sensors32, storage device34, and user interface device22.

Processing circuitry20may include one or more processors that are configured to implement functionality and/or process instructions for execution within computing device12. For example, processing circuitry20may be capable of processing instructions stored in storage device34. Processing circuitry20may include, for example, microprocessors, a digital signal processors (DSPs), an application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), complex programmable logic devices (CPLDs), or equivalent integrated or discrete logic circuitry, or a combination of any of the foregoing devices or circuitry. Accordingly, processing circuitry20may include any suitable structure, whether in hardware, software, firmware, or any combination thereof, to perform the functions ascribed herein to processing circuitry20.

User interface device22includes a display (not shown), such as a liquid crystal display (LCD) or a light emitting diode (LED) display or other type of screen, with which processing circuitry20may present health- or device-related information, e.g., cardiac EGMs. In addition, user interface device22may include an input mechanism to receive input from the user. The input mechanisms may include, for example, any one or more of buttons, a keypad (e.g., an alphanumeric keypad), a peripheral pointing device, a touch screen, or another input mechanism that allows the user to navigate through user interface device22presented by processing circuitry20of computing device12and provide input.

Communication circuitry26may include any suitable hardware, firmware, software or any combination thereof for communicating with another device, such as pacemakers10. Under the control of processing circuitry20, communication circuitry26may receive downlink telemetry from, as well as send uplink telemetry to, pacemakers10, or another device. Communication circuitry26may be configured to transmit or receive signals via inductive coupling, electromagnetic coupling, NFC, RF communication, Bluetooth®, Wi-Fi™, or other proprietary or non-proprietary wireless communication schemes. Communication circuitry26may also be configured to communicate with devices other than pacemakers10via any of a variety of forms of wired and/or wireless communication and/or network protocols.

Data exchanged between computing device12and pacemakers10may include operational parameters of pacemakers10. Computing device12may transmit data, including computer-readable instructions, to pacemakers10. Pacemakers10may receive and implement the computer-readable instructions. In some examples, the computer-readable instructions, when implemented by pacemakers10, may control pacemakers10to change one or more operational parameters, export collected data, etc.

One or more sensors32may be configured to sense, measure, and/or collect information regarding computing device12and/or patient4. Storage device34may be configured to store information within computing device12during operation. Storage device34may include a computer-readable storage medium or computer-readable storage device. In some examples, storage device34includes one or more of a short-term memory or a long-term memory. Storage device34may include, for example, read-only memory (ROM), random access memory (RAM), non-volatile RAM (NVRAM), Dynamic RAM (DRAM), Static RAM (SRAM), magnetic discs, optical discs, flash memory, forms of electrically-erasable programmable ROM (EEPROM) or erasable programmable ROM (EPROM), or any other digital media. In some examples, storage device34is used to store data indicative of instructions for execution by processing circuitry20. Storage device34may also be used to store data as a result of operations performed by processing circuitry20.

Processing circuitry20may be configured to communicate, via communication circuitry26, with pacemakers10A and10B implanted in heart6of patient4to synchronize the rate response pacing of pacemakers10A and10B, such that pacemakers10A and10B may perform cardiac pacing of heart6at similar rates. In some examples, processing circuitry20may be configured to synchronize the rate response between pacemakers10A and10B by synchronizing the activity counts determined by pacemakers10A and10B. Pacemakers10A and10B may each determine the activity level of patient4in the form of an activity count, which is a value that corresponds to the activity level of patient4.

Synchronizing the rate response pacing of pacemakers10A and10B do not necessarily mean that pacemakers10A and10B perform cardiac pacing of heart6at the same pacing rates. In some examples, synchronizing the rate response pacing of pacemakers10A and10B may cause pacemakers10A and10B to perform cardiac pacing of heart6at a pacing rate that differs by no more than a threshold value or a threshold percentage. In some examples, synchronizing the rate response pacing of pacemakers10A and10B may cause pacemakers10A and10B to perform cardiac pacing of heart6at pacing rates that differs by a fixed pacing rate, such as a fixed difference in bpm.

In some examples, synchronizing rate response pacing of pacemakers10A and10B may cause the difference between the pacing rates of pacemakers10A and10B to change when in different pacing rate ranges. For example, synchronizing the rate response pacing of pacemakers10A and10B may cause pacemakers10A and10B to perform cardiac pacing of heart6at pacing rates that differs by a first fixed value when the pacing rates are between the lower rate and the adjusted daily living rate, and to perform cardiac pacing of heart6at pacing rates that differs by a second fixed value different from the first fixed value when the pacing rates are between the adjusted daily living rate and the upper rate.

To synchronize the activity counts determined by pacemakers10A and10B, patient4may undergo a triggered exercise test that includes at least a period during which patient4performs moderate exercise and at least a period during which patient4is at rest. During the triggered exercise test, each of pacemakers10A and10B may collect rate responsive pacing data, which may be detailed information such as the activity counts, pacing rates, parameters of the activity sensors of pacemakers10A and10B, the accelerometer signals generated by the activity sensors of pacemakers10A and10B, and the like.

Processing circuitry20may be configured to receive, from pacemakers10A and10B, the rate responsive pacing data collected by pacemakers10A and10B and to synchronize the rate response between pacemaker10A and pacemaker10B based at least in part on the rate responsive pacing data collected by pacemakers10A and10B during the triggered exercise test by matching the activity counts between pacemakers10A and10B. In some examples, given a set of activity counts generated by pacemaker10A during the triggered exercise test and a set of activity counts generated by pacemaker10B during the triggered exercise test, processing circuitry20may be configured to modify the parameters of one or both of the activity sensors and/or the activity count algorithm used by one or both of pacemakers10A and10B to generate the activity counts so that the activity counts generated by pacemaker10A during the triggered exercise test matches the activity counts generated by pacemaker10B during the triggered exercise test.

In some examples, processing circuitry20may be configured to modify parameters such as the blanking period, the filter, and the gain of the activity sensor of pacemaker10A to generate activity counts from the signals measured by pacemaker10A during the triggered exercise test that matches the activity counts generated by pacemaker10B during the triggered exercise test. Computing device12may therefore be configured to program pacemaker10A with the modified parameters of the activity sensor of pacemaker10A and/or the modified activity count algorithm used by pacemaker10A.

In some examples, processing circuitry20may be configured to synchronize the rate response between pacemaker10A and pacemaker10B based at least in part on the rate responsive pacing data collected by pacemakers10A and10B during the triggered exercise test by matching rate response slopes of pacemakers10A and10B during the triggered exercise test. To match the rate response slopes of pacemakers10A and10B, computing device12may modify the rate responsive algorithm(s) of pacemaker10A and/or pacemaker10B so that the rate response slope of pacemaker10A during the triggered exercise test matches (e.g., is the same as) the rate response slope of pacemaker10B during the triggered exercise test without modifying the activity counts generated by either pacemaker10A or pacemaker10B.

Pacemaker10A and pacemaker10B may each use a rate response algorithm to determine, given an activity count, a pacing rate. Computing device12may therefore be configured to use the rate response slope of pacemaker10B as a reference to modify a rate response algorithm of pacemaker10A, so that pacemaker10A may generate, based on the modified rate response algorithm, a rate response slope from the activity counts of pacemaker10A during the triggered exercise test that matches the rate response slope of pacemaker10B during the triggered exercise test.

In some examples, when the rate response slope includes a rate response slope in the ADL range and a rate response slope in the exertion range, computing device12may be configured to modify a rate response algorithm of pacemaker10A associated with the rate response slope in the ADL range and to modify a rate response algorithm of pacemaker10A associated with the rate response slope in the exertion range. Pacemaker10A may generate, based on the modified response algorithm associated with the rate response slope in the ADL range, a rate response slope in the ADL range from the activity counts of pacemaker10A during the triggered exercise test that matches the rate response slope of pacemaker10B in the ADL range during the triggered exercise test. Similarly, pacemaker10A may generate, based on the modified response algorithm associated with the rate response slope in the exertion range, a rate response slope in the exertion range from the activity counts of pacemaker10A during the triggered exercise test that matches the rate response slope of pacemaker10B in the exertion range during the triggered exercise test.

In some examples, processing circuitry20may be configured to modify the rate response algorithm of pacemaker10A as well as the rate response algorithm of pacemaker10B to achieve a specified target pacing rate given a specified activity level. For example, processing circuitry20may be configured to modify the rate response algorithm of pacemaker10A as well as the rate response algorithm of pacemaker10B to achieve a target pacing rate of 100 beats per minute (bpm) when patient4is performing moderate exercise. Computing device12may therefore be configured to modify the rate response algorithm of pacemaker10A to produce, given the activity counts generated by pacemaker10A while patient4is performing moderate exercise, a targeted pacing rate (e.g., 100 bpm). Similarly, processing circuitry20may be configured to modify the rate response algorithm of pacemaker10B to produce, given the activity counts generated by pacemaker10B while patient4is performing moderate exercise, a targeted pacing rate (e.g., 100 bpm). Computing device12may therefore be configured to program pacemaker10A and/or pacemaker10B with the modified rate response algorithm.

In some examples, processing circuitry20may be configured to modify the rate response slopes of pacemakers10A and10B to match the sensor rate histograms between pacemakers10A and10B. That is, processing circuitry20may be configured to modify the rate response algorithm of pacemaker10A and/or pacemaker10to generate, for a given time period, the same distribution of pacing rates by pacemakers10A and10B. A sensor rate histogram for a pacemaker is a graph that illustrates range distributions of the pacing rate of the pacemaker. Processing circuitry20may be configured to, at a follow-up clinical visit by patient4, download or otherwise receive sensor rate data from pacemakers10A and10B. Such sensor rate data may be data sensed and stored by pacemakers10A and10B since the previous follow-up. Processing circuitry20may be configured to collate or otherwise process the sensor rate data from pacemakers10A and10B to determine a sensor rate histogram for pacemaker10A indicative of the distribution of pacing rates by pacemaker10A during the period since the last follow-up clinical visit and a sensor rate histogram for10B indicative of the distribution of pacing rates by pacemaker10bduring the period since the last follow-up clinical visit.

Processing circuitry20may be configured to receive sensor rate data from pacemaker10A and to determine, based on the sensor rate data from pacemaker10A, a sensor rate histogram for pacemaker10A. Similarly, processing circuitry20may be configured to receive sensor rate data from pacemaker10B and to determine, based on the sensor rate data from pacemaker10B, a sensor rate histogram for pacemaker10B. Sensor rate data received from pacemakers10A and10B may be information regarding the pacing rates of each of pacemakers10A and10B over time since the last follow-up clinical visit by patient4, the activity counts associated with the pacing rates of each of pacemakers10A and10B over time since the last follow-up clinical visit by patient4, and the like.

Processing circuitry20may be configured to modify the rate response slope of at least one of pacemaker10A and pacemaker10B so that the sensor rate histogram of pacemaker10A matches (e.g., is the same as) the sensor rate histogram of pacemaker10B. In some examples, processing circuitry20may be configured to modify rate response slope of pacemaker10A by modifying or determining a rate response algorithm for pacemaker10A, such that the rate response algorithm is usable by pacemaker10A to generate, based on the activity counts associated with the pacing rates of pacemakers10A since the last follow-up clinical visit by patient4, associated pacing rates having distribution that matches the distribution of pacing rates of pacemaker10B over time since the last follow-up clinical visit by patient4, which corresponds to the second sensor rate histogram. Computing device12may therefore cause pacemaker10A to use the determined rate response algorithm for determining pacing rates based on activity counts, such as by programming pacemaker10A to use the determined rate response algorithm, sending an indication of the determined rate response slope to pacemaker10A, and the like.

In some examples, processing circuitry20may be configured to modify the rate response slopes of pacemakers10A and10B to match the activity count histograms between pacemakers10A and10B. That is, processing circuitry20may be configured to modify the rate response algorithm of pacemaker10A and/or pacemaker10to generate, for a given time period, the same distribution of activity by pacemakers10A and10B. An activity count histogram for a pacemaker is a graph that illustrates range distributions of the activity counts of the pacemaker. Processing circuitry20may be configured to, at a follow-up clinical visit by patient4, download or otherwise receive sensor rate data from pacemakers10A and10B. Such sensor rate data may be data sensed and stored by pacemakers10A and10B since the previous follow-up. Processing circuitry20may be configured to collate or otherwise process the sensor rate data from pacemakers10A and10B to determine an activity histogram for pacemaker10A indicative of the distribution of activity counts by pacemaker10A during the period since the last follow-up clinical visit and an activity count histogram for10B indicative of the distribution of activity counts by pacemaker10bduring the period since the last follow-up clinical visit.

Processing circuitry20may be configured to receive sensor rate data from pacemaker10A and to determine, based on the sensor rate data from pacemaker10A, an activity count histogram for pacemaker10A. Similarly, processing circuitry20may be configured to receive sensor rate data from pacemaker10B and to determine, based on the sensor rate data from pacemaker10B, an activity count histogram for pacemaker10B. Sensor rate data received from pacemakers10A and10B may be information regarding the pacing rates of each of pacemakers10A and10B over time since the last follow-up clinical visit by patient4, the activity counts associated with the pacing rates of each of pacemakers10A and10B over time since the last follow-up clinical visit by patient4, and the like.

Processing circuitry20may be configured to modify the rate response slope of at least one of pacemaker10A and pacemaker10B so that the activity count histogram of pacemaker10A matches (e.g., is the same as) the activity count histogram of pacemaker10B. In some examples, processing circuitry20may be configured to modify rate response slope of pacemaker10A by modifying or determining a rate response algorithm for pacemaker10A, such that the rate response algorithm is usable by pacemaker10A to generate, based on the activity counts associated with the pacing rates of pacemakers10A since the last follow-up clinical visit by patient4, associated activity counts having distribution that matches the distribution of pacing rates of pacemaker10B over time since the last follow-up clinical visit by patient4, which corresponds to the second activity count histogram. Computing device12may therefore cause pacemaker10A to use the determined rate response algorithm for determining pacing rates based on activity counts, such as by programming pacemaker10A to use the determined rate response algorithm, sending an indication of the determined rate response slope to pacemaker10A, and the like.

FIG.4is a block diagram of an example configuration of pacemaker10ofFIG.2in accordance with the techniques of the disclosure. Pacemaker10includes a pulse generation circuit202, a sensing circuit204, a control circuit206, memory210, telemetry circuit208, motion sensor212and a power source214.

Motion sensor212, also referred to throughout this disclosure as an activity sensor, may be a multi-axis sensor, e.g., a two-dimensional or three-dimensional sensor, with each axis providing a signal that may be analyzed individually or in combination for detecting cardiac mechanical events. In the example ofFIG.4, motion sensor212is implemented as an accelerometer and may also be referred to herein as “accelerometer212.” However, in other examples, motion sensor212is another type of motion sensor or mechanical sensor capable of detecting mechanical motion of heart6, such as a piezoelectric sensor or a MEMS device. Motion sensor212produces an electrical signal correlated to mechanical motion or vibration of sensor212(and pacemaker10), e.g., when subjected to flowing blood and cardiac motion. The motion sensor212may include, e.g., filters, amplifiers, rectifiers, an ADC and/or other components for producing a mechanical motion signal passed to control circuit206. For example, each vector signal corresponding to each individual axis of a multi-axis accelerometer may be filtered by a high pass filter, e.g., a 10 Hz high pass filter, and rectified for use by atrial event detector circuit240for detecting atrial systolic events. The high pass filter may be lowered (e.g., to 5 Hz) if needed to detect atrial signals that have lower frequency content. In some examples, high pass filtering is performed with no low pass filtering. In other examples, each accelerometer axis signal is filtered by a low pass filter, e.g., a 30 Hz low pass filter, with or without high pass filtering.

Motion sensor212may be a one-dimensional, single axis accelerometer, two-dimensional or three-dimensional multi-axis accelerometer. One example of an accelerometer for use in implantable medical devices is generally disclosed in U.S. Pat. No. 5,885,471 to Ruben, et al., entitled “Shock resistant accelerometer for implantable medical device,” filed on Jul. 31, 1997 and issued on Mar. 23, 1999, the entire content of which is incorporated herein by reference. Additional detail with respect to an implantable medical device arrangement including a piezoelectric accelerometer for detecting patient motion is set forth in U.S. Pat. No. 4,485,813 to Anderson, et al., entitled “Implantable dynamic pressure transducer system,” filed on Nov. 19, 1981, and issued on Dec. 4, 1984, and U.S. Pat. No. 5,052,388 to Sivula, et al., entitled “Method and apparatus for implementing activity sensing in a pulse generator,” filed on Dec. 22, 1989, and issued on Oct. 1, 1991, the entire contents of each of which is incorporated by reference herein. Examples of three-dimensional accelerometers that may be implemented in pacemaker10and used for detecting cardiac mechanical events is set forth in in U.S. Pat. No. 5,593,431 to Sheldon, entitled “Medical service employing multiple DC accelerometers for patient activity and posture sensing and method,” filed on Mar. 30, 1995 and issued on Jan. 14, 1997, and U.S. Pat. No. 6,044,297 to Sheldon, entitled “Posture and device orientation and calibration for implantable medical devices,” filed on Sep. 25, 1998, and issued on Mar. 28, 2000, the entire contents of each of which are incorporated herein by reference. Other accelerometer designs may be used for producing an electrical signal that is correlated to motion imparted on pacemaker10due to ventricular and atrial events.

The various circuits represented inFIG.4may be combined on one or more integrated circuit boards which include a specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, state machine or other suitable components that provide the described functionality.

Sensing circuit204is configured to sense electrogram data by sensing a cardiac electrical signal via electrodes162and164by a pre-filter and amplifier circuit220. Pre-filter and amplifier circuit220may include a high pass filter to remove DC offset, e.g., a 2.5 to 5 Hz high pass filter, or a wideband filter having a passband of 2.5 Hz to 100 Hz to remove DC offset and high frequency noise. Pre-filter and amplifier circuit220may further include an amplifier to amplify the “raw” cardiac electrical signal passed to rectifier and amplifier circuit222and analog-to-digital converter (ADC)226. ADC226may pass a multi-bit, digital electrogram (EGM) signal to control circuit206for use, in some cases, by atrial event detector circuit240for detecting atrial electrical events, such as P-waves. For example, atrial event detector circuit240may use identification of atrial electrical events in algorithms for detecting atrial systolic events from the mechanical motion signal provided by motion sensor212. The amplified signal of pre-filter and amplifier circuit220may also be passed to rectifier and amplifier circuit222, which may include a rectifier, bandpass filter, and amplifier for passing a cardiac signal to ventricular event detector circuit224for use in identifying ventricular electrical events (e.g., R-waves or T-waves).

Ventricular event detector circuit224may include a sense amplifier or other detection circuitry that compares the incoming rectified, cardiac electrical signal to a ventricular event detection threshold, which may be an auto-adjusting threshold. In some examples, ventricular event detector circuit224is configured to detect ventricular events, such as an R-wave or a T-wave. When the incoming signal crosses the ventricular event detection threshold, ventricular event detector circuit224produces a sensed ventricular event signal (e.g., which may be an R-sense signal where an R-wave is detected) that is passed to control circuit206. In other examples not expressly depicted in the example ofFIG.3, ventricular event detector circuit224may be configured to receive a digital output of ADC226for detecting ventricular events by a comparator, morphological signal analysis of the digital EGM signal, or to perform other ventricular event detection techniques. Sensed ventricular event signals passed from ventricular event detector circuit224to control circuit206may be used for scheduling ventricular pacing pulses by pace timing circuit242and for use in identifying the timing of ventricular electrical events in algorithms performed by atrial event detector circuit240for detecting atrial systolic events from a signal received from motion sensor212.

Control circuit206includes an atrial event detector circuit240, pace timing circuit242, and processing circuitry244. Atrial event detector circuit240is configured to detect atrial mechanical events from a signal received from motion sensor212. In some examples, one or more ventricular mechanical events may be detected from the motion sensor signal in a given cardiac cycle to facilitate positive detection of the atrial systolic event from the motion sensor signal during the ventricular cycle.

Control circuit206may receive sensed ventricular event signals, such as sensed R-wave events, and/or digital electrogram data from sensing circuit204for use in detecting and confirming cardiac events and controlling ventricular pacing. For example, R-wave sensed event signals may be passed to pace timing circuit242for inhibiting scheduled ventricular pacing pulses or scheduling ventricular pacing pulses when pacemaker10is operating in a non-atrial tracking (asynchronous) ventricular pacing mode. R-wave sensed event signals may also be passed to atrial event detector circuit240for use in setting time windows used by control circuit206for detecting atrial systolic events from the motion sensor signal.

Atrial event detector circuit240receives a mechanical motion signal from motion sensor212and may start an atrial refractory period in response to a ventricular electrical event, e.g., an R-wave sensed event signal from sensing circuit204or delivery of a ventricular pacing pulse by pulse generation circuit202. In some examples, atrial event detector circuit240determines if the motion sensor signal satisfies atrial mechanical event detection criteria outside of the refractory period. The motion sensor signal during the refractory period may be monitored by atrial event detector circuit240for the purposes of detecting ventricular mechanical events, which may be used for confirming or validating atrial systolic event detection. As such, ventricular mechanical event detection windows may be set during the atrial refractory period and may be set according to predetermined time intervals following identification of a ventricular electrical event.

Pace timing circuit242(or processing circuitry244) may additionally receive sensed ventricular event signals, such as sensed R-wave event signals, from ventricular event detector circuit224for use in controlling the timing of pacing pulses delivered by pulse generation circuit202. In some examples, processing circuitry244is one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuitry, as well as any combinations of such components. Processing circuitry244may include one or more clocks for generating clock signals that are used by pace timing circuit242to time out an AV pacing interval that is started upon receipt of an atrial event detection signal from atrial event detector circuit240. Pace timing circuit242may include one or more pacing escape interval timers or counters that are used to time out the AV pacing interval, which may be a programmable interval stored in memory210and retrieved by processing circuitry244for use in setting the AV pacing interval used by pace timing circuit242.

Pace timing circuit242may additionally include a lower pacing rate interval timer for controlling a lower ventricular pacing rate. For example, if an atrial systolic event is not detected from the motion sensor signal, thus not initiating the programmed AV pacing interval for triggering a ventricular pacing pulse, a ventricular pacing pulse may nevertheless be delivered by pulse generation circuit202upon expiration of the lower pacing rate interval to prevent ventricular asystole and maintain a minimum ventricular rate.

Processing circuitry244may retrieve other programmable pacing control parameters, such as pacing pulse amplitude and pacing pulse width, which are passed to pulse generation circuit202for controlling pacing pulse delivery from memory210. In addition to providing control signals to pace timing circuit242and pulse generation circuit202for controlling pacing pulse delivery, processing circuitry244may provide sensing control signals to sensing circuit204, e.g., ventricular event sensing thresholds such as an R-wave sensing threshold, sensitivity, and/or various blanking and refractory intervals applied to the electrogram data.

Pulse generation circuit202generates electrical pacing pulses that are delivered to the RV of the patient's heart via cathode electrode164and return anode electrode162. Pulse generation circuit202may include charging circuit230, switching circuit232and an output circuit234. Charging circuit230may include a holding capacitor that may be charged to a pacing pulse amplitude by a multiple of the battery voltage signal of power source214under the control of a voltage regulator. The pacing pulse amplitude may be set based on a control signal from control circuit206. Switching circuit232may control when the holding capacitor of charging circuit230is coupled to the output circuit234for delivering the pacing pulse. For example, switching circuit232may include a switch that is activated by a timing signal received from pace timing circuit242upon expiration of an AV pacing interval, a VV rate smoothing interval, or VV lower rate pacing interval) and kept closed for a programmed pacing pulse width to enable discharging of the holding capacitor of charging circuit230. The holding capacitor, previously charged to the pacing pulse voltage amplitude, is discharged across electrodes162and164through the output capacitor of output circuit234for the programmed pacing pulse duration. Additional description of pacing circuitry is set forth in U.S. Pat. No. 5,507,782 to Kieval, et al., entitled “Method and apparatus for dual chamber cardiac pacing,” filed on Mar. 17, 1994 and issued on Apr. 16, 1996 and U.S. Pat. No. 8,532,785 to Crutchfield, et al., entitled “Therapy delivery method and system for implantable medical devices,” filed on Sep. 26, 2012, and issued on Sep. 10, 2013, the entire contents of each of which are incorporated herein by reference. Such pacing circuitry described by U.S. Pat. Nos. 5,507,782 and 8,532,785 may be implemented in pacemaker10for charging a pacing capacitor to a predetermined pacing pulse amplitude under the control of control circuit206and delivering a pacing pulse.

Memory210may include computer-readable instructions that, when executed by control circuit206, cause control circuit206to perform various functions attributed throughout this disclosure to pacemaker10. The computer-readable instructions may be encoded within memory210. Memory210may include any non-transitory, computer-readable storage media including any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), flash memory, or other digital media.

Memory210may store event detection parameters250, such as timing intervals and other data used by control circuit206to control the delivery of pacing pulses by pulse generation circuit202, e.g., by detecting an atrial systolic event by atrial event detector circuit240from the motion sensor signal and controlling the timing of delivery of ventricular pacing pulse delivery by pulse generation circuit202. Such event detection parameters250may include, e.g., a beginning or an ending of a detection window for sensing an A7event, a beginning or an ending of a detection window for sensing an A4event, a threshold amplitude for the detection window for sensing the A7event (e.g., such as a minimum threshold or a maximum threshold), a threshold amplitude for the detection window for sensing the A4event (e.g., such as a minimum threshold or a maximum threshold), or a boundary separating the window for sensing the A7event from the window for sensing the A4event, etc.

Power source214provides power to each of the other circuits and components of pacemaker10as required. Power source214may include one or more energy storage devices, such as one or more rechargeable or non-rechargeable batteries. The connections between power source214and other pacemaker circuits and components are not shown inFIG.4for the sake of clarity but are to be understood from the general block diagram ofFIG.4. For example power source214may provide power to charging circuit230for charging a holding capacitor to a pacing voltage amplitude, current to switching circuit232and other circuitry included in pulse generation circuit202as needed, power to transceiver209, motion sensor212, and ADC226and other circuitry of sensing circuit204as needed as well as memory210.

Telemetry circuit208includes a transceiver209and antenna211for transferring and receiving data via a radio frequency (RF) communication link. Telemetry circuit208may be capable of bi-directional communication with computing device12(FIG.1) as described above. Mechanical motion data and electrogram data may be transmitted by telemetry circuit208to computing device12. Furthermore, event detection parameters, pacing control parameters, and algorithms for performing atrial event detection and/or ventricular pacing control may be received by telemetry circuit208and stored in memory210for access by control circuit206.

FIG.5is a flowchart illustrating an example operation in accordance with the techniques of the disclosure. For convenience,FIG.5is described with respect toFIGS.1-4.

As depicted inFIG.5, processing circuitry20of computing device12and/or processing circuitry50of pacemaker10may receive one or more sensor values indicative of motion of a patient4(402). For example, processing circuitry20may receive accelerometer data from an accelerometer36or from any other one or more sensors32for sensing motion. Similarly, processing circuitry50may receive accelerometer data from an accelerometer59or from any other one or more sensors58for sensing motion.

Processing circuitry20of computing device12may receive, from a first pacemaker10A implanted in a heart6of a patient4, first rate responsive pacing data (404). Processing circuitry20may receive, from a second pacemaker10B implanted in the heart6of the patient4, second rate responsive pacing data (404). Processing circuitry20may synchronize, based at least in part on the first rate responsive pacing data and the second rate responsive pacing data, rate responsive pacing of the first pacemaker10A and the second pacemaker10B (406).

In some examples, the techniques of the disclosure include a system that comprises means to perform any method described herein. In some examples, the techniques of the disclosure include a computer-readable medium comprising instructions that cause processing circuitry to perform any method described herein.

The techniques of this disclosure includes the following examples.

Example 1: A method includes receiving, by processing circuitry from a first pacemaker implanted in a heart of a patient, first rate responsive pacing data; receiving, by the processing circuitry from a second pacemaker implanted in the heart of the patient, second rate responsive pacing data; and synchronizing, by the processing circuitry and based at least in part on the first rate responsive pacing data and the second rate responsive pacing data, rate responsive pacing of the first pacemaker and the second pacemaker.

Example 2: The method of example 1, wherein: the first rate responsive pacing data is collected by the first pacemaker as the patient undergoes a triggered exercise test; and the second rate responsive pacing data is collected by the second pacemaker as the patient undergoes the triggered exercise test.

Example 3: The method of example 2, wherein the triggered exercise test includes at least a period of rest for the patient and a period of moderate exercise for the triggered exercise test.

Example 4: The method of any of examples 2 and 3, wherein: the first rate responsive pacing data includes first activity counts generated by the first pacemaker during the triggered exercise test based at least in part on a first accelerometer data generated by a first activity sensor of the first pacemaker and a first activity counts algorithm; the second rate responsive pacing data includes second activity counts generated by the second pacemaker during the triggered exercise test based at least in part on a second accelerometer data generated by a second activity sensor of the second pacemaker and a second activity counts algorithm; and synchronizing the rate responsive pacing of the first pacemaker with the rate responsive pacing of the second pacemaker further comprises modifying, by the processing circuitry, at least one of: the first activity counts algorithm of the first pacemaker or one or more parameters of the first activity sensor such that the first pacemaker is able to generate, from the first rate responsive pacing data, first activity counts that match the second activity counts generated by the second pacemaker during the triggered exercise test.

Example 5: The method of example 4, wherein modifying at least one of: the first activity counts algorithm of the first pacemaker or the one or more parameters of the first activity sensor further comprises: programming, by the processing circuitry, the first pacemaker to modify at least one of: associations between activity counts and pacing rates of the first pacemaker or the one or more parameters of the first activity sensor.

Example 6: The method of any of examples 2-5, wherein: the first rate responsive pacing data includes first activity counts generated by the first pacemaker during the triggered exercise test based at least in part on first accelerometer data generated by a first activity sensor of the first pacemaker and a first rate response slope; the second rate responsive pacing data includes second activity counts generated by the second pacemaker during the triggered exercise test based at least in part on second accelerometer data generated by a second activity sensor of the second pacemaker and a second rate response slope; and synchronizing the rate responsive pacing of the first pacemaker with the rate responsive pacing of the second pacemaker further comprises modifying associations between the first activity counts and pacing rates of the first pacemaker to modify the first rate response slope of the first pacemaker to match the second rate response slope of the second pacemaker.

Example 7: The method of any of examples 2-5, wherein: the first rate responsive pacing data includes first activity counts generated by the first pacemaker during the triggered exercise test based at least in part on first accelerometer data generated by a first activity sensor of the first pacemaker and a first rate response slope associated with first associations between activity counts and pacing rates of the first pacemaker; the second rate responsive pacing data includes second activity counts generated by the second pacemaker during the triggered exercise test based at least in part on second accelerometer data generated by a second activity sensor of the second pacemaker and a second rate response slope generated associated with second associations between activity counts and pacing rates of the second pacemaker; and synchronizing the rate responsive pacing of the first pacemaker with the rate responsive pacing of the second pacemaker further comprises modifying, by the processing circuitry, the first associations between activity counts and pacing rates of the first pacemaker and the second associations between activity counts and pacing rates of the second pacemaker, such that each of the first pacemaker and the second pacemaker is able to achieve a specified target pacing rate given a specified activity level of the patient.

Example 8: The method of any of examples 1 through 7, wherein the first rate responsive pacing data is collected by the first pacemaker over a period of time since a last follow-up clinical visit by the patient; and the second rate responsive pacing data is collected by the second pacemaker over the period of time since the last follow-up clinical visit by the patient.

Example 9: The method of example 8, wherein: the first rate responsive pacing data includes first pacing rate data and activity counts generated by the first pacemaker; the second rate responsive pacing data includes second pacing rate data; and synchronizing the rate responsive pacing of the first pacemaker with the rate responsive pacing of the second pacemaker further comprises: generating, by the processing circuitry, a first sensor rate histogram based at least in part on the first pacing rate data; generating, by the processing circuitry, a second sensor rate histogram based at least in part on the second pacing rate data; and determining, by the processing circuitry, a rate response algorithm for the first pacemaker, such that the rate response algorithm is usable to generate, based on the activity counts, pacing rate data having a sensor rate histogram that matches the second sensor rate histogram.

Example 10: The method of any of examples 8 and 9, wherein: the first rate responsive pacing data includes first pacing rate data and first activity counts generated by the first pacemaker; the second rate responsive pacing data includes second activity counts generated by the second pacemaker; and synchronizing the rate responsive pacing of the first pacemaker with the rate responsive pacing of the second pacemaker further comprises: generating, by the processing circuitry, a first activity counts histogram based at least in part on the first pacing rate data; generating, by the processing circuitry, a second activity counts histogram based at least in part on the second pacing rate data; and determining, by the processing circuitry, a rate response algorithm for the first pacemaker, such that the rate response algorithm is usable to generate pacing rate data having an activity count histogram that matches the second activity counts histogram.

Example 11: The method of any of examples 9 and 10, wherein synchronizing the rate responsive pacing of the first pacemaker with the rate responsive pacing of the second pacemaker further comprises: programming, by the processing circuitry, the first pacemaker to use the rate responsive algorithm for pacing the patient.

Example 12: The method of any of examples 1-11, wherein the first pacemaker is disposed in an atrium of the heart of the patient, and wherein the second pacemaker is disposed in a ventricle of the heart of the patient.

Example 13: A medical device includes memory; and processing circuitry operably coupled to the memory and configured to: receive, from a first pacemaker implanted in a heart of a patient, first rate responsive pacing data; receive, from a second pacemaker implanted in the heart of the patient, second rate responsive pacing data; and synchronize, based at least in part on the first rate responsive pacing data and the second rate responsive pacing data, rate responsive pacing of the first pacemaker and the second pacemaker.

Example 14: The medical device of example 13, wherein: the first rate responsive pacing data is collected by the first pacemaker as the patient undergoes a triggered exercise test; and the second rate responsive pacing data is collected by the second pacemaker as the patient undergoes the triggered exercise test.

Example 15: The medical device of example 14, wherein the triggered exercise test includes at least a period of rest for the patient and a period of moderate exercise for the triggered exercise test.

Example 16: The medical device of any of examples 14 and 15, wherein: the first rate responsive pacing data includes first activity counts generated by the first pacemaker during the triggered exercise test based at least in part on a first accelerometer data generated by a first activity sensor of the first pacemaker and a first activity counts algorithm; the second rate responsive pacing data includes second activity counts generated by the second pacemaker during the triggered exercise test based at least in part on a second accelerometer data generated by a second activity sensor of the second pacemaker and a second activity counts algorithm; and to synchronize the rate responsive pacing of the first pacemaker with the rate responsive pacing of the second pacemaker, the processing circuitry is further configured to modify at least one of: the first activity counts algorithm of the first pacemaker or one or more parameters of the first activity sensor such that the first pacemaker is able to generate, from the first rate responsive pacing data, first activity counts that match the second activity counts generated by the second pacemaker during the triggered exercise test.

Example 17: The medical device of example 16, wherein to modify at least one of: the first activity counts algorithm of the first pacemaker or the one or more parameters of the first activity sensor, the processing circuitry is further configured to: program the first pacemaker to modify at least one of: associations between activity counts and pacing rates of the first pacemaker or the one or more parameters of the first activity sensor.

Example 18: The medical device of any of examples 14-17, wherein: the first rate responsive pacing data includes first activity counts generated by the first pacemaker during the triggered exercise test based at least in part on first accelerometer data generated by a first activity sensor of the first pacemaker and a first rate response slope; the second rate responsive pacing data includes second activity counts generated by the second pacemaker during the triggered exercise test based at least in part on second accelerometer data generated by a second activity sensor of the second pacemaker and a second rate response slope; and to synchronize the rate responsive pacing of the first pacemaker with the rate responsive pacing of the second pacemaker, the processing circuitry is further configured to modify associations between the first activity counts and pacing rates of the first pacemaker to modify the first rate response slope of the first pacemaker to match the second rate response slope of the second pacemaker.

Example 19: The medical device of any of examples 14-17, wherein: the first rate responsive pacing data includes first activity counts generated by the first pacemaker during the triggered exercise test based at least in part on first accelerometer data generated by a first activity sensor of the first pacemaker and a first rate response slope associated with first associations between activity counts and pacing rates of the first pacemaker; the second rate responsive pacing data includes second activity counts generated by the second pacemaker during the triggered exercise test based at least in part on second accelerometer data generated by a second activity sensor of the second pacemaker and a second rate response slope generated associated with second associations between activity counts and pacing rates of the second pacemaker; and to synchronize the rate responsive pacing of the first pacemaker with the rate responsive pacing of the second pacemaker, the processing circuitry is further configured to modify the first associations between activity counts and pacing rates of the first pacemaker and the second associations between activity counts and pacing rates of the second pacemaker, such that each of the first pacemaker and the second pacemaker is able to achieve a specified target pacing rate given a specified activity level of the patient.

Example 20: The medical device of any of examples 13 through 19, wherein the first rate responsive pacing data is collected by the first pacemaker over a period of time since a last follow-up clinical visit by the patient; and the second rate responsive pacing data is collected by the second pacemaker over the period of time since the last follow-up clinical visit by the patient.

Example 21: The medical device of example 20, wherein: the first rate responsive pacing data includes first pacing rate data and activity counts generated by the first pacemaker; the second rate responsive pacing data includes second pacing rate data; and to synchronize the rate responsive pacing of the first pacemaker with the rate responsive pacing of the second pacemaker, the processing circuitry is further configured to: generate a first sensor rate histogram based at least in part on the first pacing rate data; generate a second sensor rate histogram based at least in part on the second pacing rate data; and determine a rate response algorithm for the first pacemaker, such that the rate response algorithm is usable to generate, based on the activity counts, pacing rate data having a sensor rate histogram that matches the second sensor rate histogram.

Example 22: The medical device of any of examples 20 and 21, wherein: the first rate responsive pacing data includes first pacing rate data and first activity counts generated by the first pacemaker; the second rate responsive pacing data includes second activity counts generated by the second pacemaker; and to synchronize the rate responsive pacing of the first pacemaker with the rate responsive pacing of the second pacemaker, the processing circuitry is further configured to: generate a first activity counts histogram based at least in part on the first pacing rate data; generate a second activity counts histogram based at least in part on the second pacing rate data; and determine a rate response algorithm for the first pacemaker, such that the rate response algorithm is usable to generate pacing rate data having an activity count histogram that matches the second activity counts histogram.

Example 23: The medical device of any of examples 21 and 22, wherein to synchronize the rate responsive pacing of the first pacemaker with the rate responsive pacing of the second pacemaker, the processing circuitry is further configured to: program the first pacemaker to use the rate responsive algorithm for pacing the patient.

Example 24: The medical device of any of examples 13-23, wherein the first pacemaker is disposed in an atrium of the heart of the patient, and wherein the second pacemaker is disposed in a ventricle of the heart of the patient.

Example 25: A non-transitory computer-readable medium includes receive, from a first pacemaker implanted in a heart of a patient, first rate responsive pacing data; receive, from a second pacemaker implanted in the heart of the patient, second rate responsive pacing data; and synchronize, based at least in part on the first rate responsive pacing data and the second rate responsive pacing data, rate responsive pacing of the first pacemaker and the second pacemaker.

Example 26: A non-transitory computer-readable medium comprising instructions that, when executed by processing circuitry of a medical device, cause the medical device to perform any of the methods of examples 1-12.

Example 27: An apparatus includes means for receiving, from a first pacemaker implanted in a heart of a patient, first rate responsive pacing data; means for receiving, from a second pacemaker implanted in the heart of the patient, second rate responsive pacing data; and means for synchronizing, based at least in part on the first rate responsive pacing data and the second rate responsive pacing data, rate responsive pacing of the first pacemaker and the second pacemaker.

Example 28: An apparatus comprising means for performing any of the methods of examples 1-12.

Example 29: A medical device includes memory; and processing circuitry operably coupled to the memory and configured to perform any of the methods of claims1-12.

Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” or “processing circuitry” as used herein may refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements.