A leadless cardiac pacemaker device configured to provide intracardiac pacing

Abstract

To provide a leadless pacemaker device configured to provide intra-cardiac pacing.SOLUTION: A pacemaker device configured to provide intra-cardiac pacing includes processing circuitry configured to generate ventricular pacing signals for stimulating a ventricle, and a reception device for receiving a sensing signal indicative of an atrial activity. The processing circuitry is configured to determine an atrial sense rate of an atrial event derived from the sensing signal. In the case where a valid atrial sense rate is determined, the processing circuitry is further configured to: determine a ventricular pacing rate according to the atrial sense rate based on a calculated atrial-ventricular (AV) delay; determine a correction value (CV) based on a timing relation between VAtrue and a calculated ventricular-atrial delay (VAcalc); and adjust the ventricular pacing rate based on the correction value (CV).SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates generally to leadless cardiac pacemaker devices that provide intracardiac pacing, and ventricular pacing in particular. [Background technology]

[0002] In recent years, leadless pacemakers have attracted increasing attention. Leadless pacemakers avoid leads because the pacemaker device itself is implanted within the heart, as opposed to subcutaneously implanted pacemakers with leads that extend transvenously into the heart. The pacemaker is in the form of a capsule that is implanted within cardiac tissue, specifically within the right ventricular wall of the right ventricle. Such leadless pacemakers offer the inherent advantage of not using leads, and can reduce patient risks associated with transvenous cardiac access by leads, such as the risks of pneumothorax, lead dislodgement, cardiac perforation, venous thrombosis, etc.

[0003] A leadless pacemaker may be specifically designed for implantation in the right ventricle, where the pacemaker is placed in or on the wall of the right ventricle during implantation. Ventricular pacing may be necessary, for example, when the AV node is dysfunctional but the sinus node has normal and adequate function. In such cases, so-called VDD pacing may be specifically desired, which requires ventricular pacing with atrial tracking and therefore sensing atrial activity to pace the ventricle based on intrinsic atrial contractions.

[0004] Pacing using atrial tracking is specifically motivated by the hemodynamic benefits in atrioventricular (AV) synchronized patients by utilizing adequate sinus node function to trigger ventricular pacing, potentially maximizing ventricular preload, limiting AV valve regurgitation, maintaining low mean atrial pressure, and modulating autonomic and neurohumoral reflexes.

[0005] There are publications exploring solutions using modalities for detecting mechanical events of atrial contraction, including sensing of motion, sound, and pressure. For example, U.S. Patent Application Publication No. 2018 / 0021581 A1 discloses a leadless cardiac pacemaker with a pressure sensor and / or an accelerometer for determining atrial contraction timing. Because mechanical events generally exhibit small signal amounts, signal detection based on mechanical events, such as motion, sound, or pressure, can be difficult to sense, especially when the leadless pacemaker device is placed in the ventricle and thus quite far from the atrium whose contraction is to be sensed. In addition, wall motion and blood flow caused by atrial contraction may not be transferred directly to the ventricle, and cardiac hemodynamic signals such as motion, heart sounds, and pressure can be affected by external factors such as posture and patient activity.

[0006] EP 3 218 049 B1 describes a leadless pacemaker device configured for implantation in a ventricle of a patient's heart and configured to switch from an atrioventricular synchronous pacing mode to an asynchronous pacing mode in response to detection of one or more atrial desensed events.

[0007] US Patent Application Publication No. 2018 / 0028814A1 discloses an implantable medical device system that operates in an atrial synchronized ventricular pacing mode and switches to an atrial asynchronous pacing mode if pacing mode switching criteria are met. A control circuit of the system detects a change in cycle length between two atrial cycle lengths determined from a cardiac signal including an atrial trigger event in the far-field. If the change in cycle length is greater than a threshold change, the control circuit determines whether the pacing mode switching criteria are met after detecting the cycle length change.

[0008] It is generally assumed that when a component sinus rhythm is available, it is preferable to control the ventricular pacing rate using a sinus rhythm rather than pacing in the ventricle using a rate-responsive mechanism. Such a rate-responsive mechanism typically causes adaptation of the pacing rate according to the patient's individual activity (e.g., according to accelerometer readings), so that the pacing rate is adapted, for example, depending on whether the patient is asleep or physically active or stressed. However, when sinus rhythm is not available, e.g., due to reduced sensing or sinus dysfunction, or when higher-rate atrial arrhythmias are present, pacing with sinus rhythm is no longer appropriate, and as a result, another pacing strategy, such as pacing with a rate-responsive mechanism, should be selected.

[0009] Therefore, different pacing modes may need to be applied at different times and conditions, necessitating switching between different modes. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] US Patent Application Publication No. 2018 / 0021581A1 [Patent Document 2] European Patent No. 3 218 049B1 [Patent Document 3] US Patent Application Publication No. 2018 / 0028814A1 Summary of the Invention [Problem to be solved by the invention]

[0011] In particular, it is an object to provide a leadless pacemaker device and method of operating a leadless pacemaker device that enables discriminatory switching between different pacing modes, in particular to adapt ventricular pacing to a detected atrial sensed rate. [Means for solving the problem]

[0012] Such needs are met by a leadless cardiac pacemaker device configured to provide intracardiac pacing having the features of claim 1 .

[0013] In one aspect of the invention, a pacemaker device configured to provide intracardiac pacing, the leadless pacemaker device comprising: a processing circuit configured to generate a ventricular pacing signal for stimulating a ventricle; a receiving device for receiving sensed signals indicative of atrial activity, the processing circuitry being configured to determine an atrial sensed rate of atrial events derived from the sensed signals; If a valid atrial sensed rate is determined, the processing circuitry determining a ventricular pacing rate according to the atrial sensed rate based on the calculated atrial-ventricular (AV) delay; generating at least one ventricular pacing signal at the ventricular pacing rate; A calculated ventricular-atrial delay (VA) that indicates the predicted time delay between a preceding ventricular event (Vs) and an atrial event (As). calc ) and The true occurrence of the time delay between a preceding ventricular event (Vs) and an atrial event (As) (VA true ) and measure VA true and calculate ventricular-atrial delay (VA calc determining a correction value (CV) based on a timing relationship between the adjusting the ventricular pacing rate based on a correction value (CV); The pacemaker device is further configured to:

[0014] For example, whether an atrial sensed rate is valid can be determined according to the atrial rate and / or the variability of the atrial rate. In a first example, if the atrial sensed rate derived from the sensed signal is within a range of normal atrial rates, a valid atrial sensed rate is determined. For an adult at rest, the normal atrial rate ranges from 60 to 100 bpm, which is higher during exercise. However, this range may deviate according to factors that vary from patient to patient (age, diseases, medications, fitness level, etc.). According to one embodiment, a valid atrial sensed rate is determined if the variability of the atrial rate is within a certain range indicative of a normal atrial rhythm. The variability of the atrial rhythm can be determined via the difference in time intervals between successive atrial events.

[0015] According to one embodiment, the processing circuitry is configured to determine a ventricular pacing rate based on the calculated ventricular pacing rate if a valid atrial sensed rate is not determined.

[0016] According to one embodiment, an atrial sensed rate is not valid if the atrial sensed rate is outside the range of normal atrial rates or if the atrial rate variability is outside the range of normal atrial rhythms. Alternatively, an atrial sensed rate is not valid when no atrial events are received via the receiving device, or when the noise level of the sensed signal is too high, or when atrial sensing / detection of the leadless pacemaker device is inhibited.

[0017] In one aspect, a leadless pacemaker device configured to provide intracardiac pacing comprises a processing circuit configured to generate a ventricular pacing signal to stimulate ventricular activity at a ventricular pacing rate; and a receiving device for receiving sensed signals indicative of atrial activity, the processing circuit configured to determine an atrial sensed rate of atrial events derived from the sensed signals, the processing circuit further configured to determine a compensation value based on a difference between the ventricular pacing rate and the atrial sensed rate; and adjusting the ventricular pacing rate based on the compensation value.

[0018] The leadless pacemaker device is configured to generate and emit a pacing signal, the leadless pacemaker device being positioned in a right or left ventricle such that at least one pacing electrode is in electrical contact with cardiac tissue for introducing stimulation energy to the cardiac tissue. The ventricular pacing signal is typically generated at a ventricular pacing rate, the ventricular pacing rate being adaptive based on whether an atrial sensed rate can be determined from sensed signals received via a receiving device.

[0019] Here, when an atrial sensed rate, indicative of timing between atrial events derived from a sensed signal picked up by using the receiving device, becomes available and suitable for pacing, the ventricular pacing rate is adapted based on the difference between the ventricular pacing rate (used prior to picking up the atrial sensed rate suitable for pacing) and the currently detected atrial sensed rate. Based on the difference between the ventricular pacing rate and the atrial sensed rate, a compensation value is determined and the ventricular pacing rate is adjusted based on the compensation value.

[0020] Specifically, by applying the offset, the ventricular pacing rate is adapted incrementally to synchronize with the atrial sensed rate. Thus, the ventricular pacing rate is not immediately switched to match the detected atrial sensed rate, but is incrementally adjusted to approach and converge with the atrial sensed rate. Thus, once the atrial sensed rate becomes available and usable by the pacing strategy, incremental adjustments of the ventricular pacing rate are initiated to synchronize the ventricular pacing rate with the atrial sensed rate.

[0021] By applying such a correction value, an adjustment similar to a phase-locked loop (PLL) mechanism is applied to incrementally adjust the ventricular pacing rate relative to the atrial sensed rate when the atrial sensed rate is available from the sensed receive signal and suitable for pacing. By using such a phase-locked loop mechanism, the correction value is used to incrementally adjust the ventricular pacing rate to adapt the ventricular pacing rate until its phase is synchronized with the atrial sensed rate (taking into account an offset dictated by the atrio-ventricular (AV) delay), and the correction value is adapted in a feedback loop until the phase of the ventricular pacing rate is locked to the phase of the atrial sensed rate.

[0022] In one embodiment, the processing circuit is configured to determine an atrial interval indicating a time interval between two successive atrial events. From an atrial sensed signal picked up by using the receiving device, an atrial event indicating an atrial activity due to an atrial contraction is determined, and the atrial interval indicates a time between two successive atrial events. In general, the ventricular interval, i.e., the interval between two successive ventricular pacing signals or intrinsic sensed events, should match the atrial interval, and the atrial sensed rate is the reciprocal of the atrial interval and defines the amount by which the ventricular pacing rate should be adapted to provide an atrioventricular synchronous pacing operation.

[0023] The processing circuitry, in one embodiment, can be configured to determine a calculated ventricular-atrial delay indicative of a time delay at which an atrial event is predicted to occur following a preceding ventricular paced or sensed event, where the ventricular-atrial delay can be determined, for example, from the calculated atrial-ventricular delay and a current ventricular interval (indicative of a current time interval between two successive ventricular pacing signals).

[0024] The atrial-ventricular delay is the delay that a ventricular sensed or paced signal should ideally follow an atrial event. The optimal value of the atrial-ventricular delay (AV delay for short) can be determined, for example, from the average measured atrial interval, and techniques for determining the optimal atrial-ventricular delay are well known, for example, by measuring pulsed wave Doppler of the mitral inflow at varying AV delays, or by obtaining continuous wave Doppler velocity time integral (VTI) of the aortic outflow at varying AV delays. The calculated ventricular-atrial delay can be determined by subtracting the value of the atrial-ventricular delay from the ventricular interval.

[0025] The calculated ventricular-atrial delay indicates the predicted time at which the next atrial event will occur after a preceding ventricular paced or sensed event if the ventricular rate is accurately synchronized to the atrial sensed rate. At the time a ventricular event occurs, i.e., when a ventricular paced signal is generated or an intrinsic ventricular sensed signal is sensed, a timer is started and used to measure the time that has elapsed since the last ventricular event. At the time an atrial event next occurs, this time is stored to obtain a time value of the true time at which an atrial event will occur following a preceding ventricular event, which can be set in relation to the calculated ventricular-atrial delay to determine a correction value based on such timing relationship.

[0026] Moreover, in accordance with one embodiment of the present invention, the processing circuitry determines a number of time bins and uses a VA to determine a correction value (CV). true falls in which time bin.

[0027] In one embodiment, a number of time bins can be determined based on the calculated ventricular-atrial delay, each time bin defined by a lower and upper limit and distributed in time around the calculated ventricular-atrial delay. The time bins can be aligned contiguously, one time bin following an adjacent time bin, and a central time bin can be defined such that the ventricular-atrial delay falls within the central time bin.

[0028] Preferably, according to one embodiment, the processing circuitry is configured to determine a ventricular-atrial (VA) delay feedback value, the VA delay feedback value being a calculated ventricular-atrial delay (VA calc ) and VA true and the processing circuitry is configured to calculate a correction value (CV) based on the VA delay feedback value.

[0029] Based on such time bins, a correction value can be set to progressively adapt the ventricular pacing rate to the atrial sensed rate. In particular, the processing circuitry can be configured to evaluate which time bin the true time of occurrence falls into to determine the correction value. To this end, the true time of occurrence is compared to the limits of each time bin, and if the true time of occurrence is found to fall between a lower time limit and an upper time limit of a particular time bin, the occurrence is identified as falling into that time bin.

[0030] Here, each time bin is associated with a particular setpoint that corresponds, in one embodiment, to a particular value of ventricular pacing rate adjustment. For example, the middle time bin, in which the ventricular-atrial delay falls, may have a setpoint of 0, while the preceding time bins may have progressively increasing setpoints and the succeeding time bins may have progressively decreasing setpoints.

[0031] Based on knowledge of which time bin the true time of occurrence of the atrial event being detected falls into, the compensation value can then be set to the set value for the corresponding time bin. Thus, if the true time of occurrence falls within the center time bin where the ventricular-atrial delay falls, the compensation value will be zero, resulting in no change in the ventricular pacing rate, assuming that phase matching already exists between the ventricular pacing rate and the atrial sensed rate. If the true time of occurrence falls within a time bin corresponding to a time range that precedes the calculated ventricular-atrial delay, the compensation value will be positive to increase the ventricular pacing rate, where the time bin is located farther from the center time bin as the magnitude of the compensation value increases progressively. In contrast, if the true time of occurrence falls within a time bin corresponding to a time range that follows the calculated ventricular-atrial delay, the compensation value will be negative to decrease the ventricular pacing rate, where again, the time bin is located farther from the center time bin as the magnitude of the compensation value in the present invention increases progressively.

[0032] Thus, by using the compensation value, a gradual adjustment of the ventricular pacing rate is applied, where the number of time bins can range anywhere between two or three and a significantly larger number of time bins. For example, if three time bins are used, the middle time bin can be associated with a set value of 0, the earlier time bins preceding the ventricular-atrial delay can be associated with a positive set value, and the later time bins can be associated with a negative set value.

[0033] Typically, by applying the correction value, the processing circuitry is configured to adjust the ventricular pacing rate to synchronize the ventricular pacing rate with the atrial sensed rate, where for the adjustment, a first ramping function can be applied to progressively adjust the ventricular pacing rate relative to the atrial sensed rate when the atrial sensed rate is suitable for controlling ventricular pacing.

[0034] The first ramping function may provide linear ramping at a predetermined ramping slope, however, the first ramping function may also provide non-linear adjustment of the ventricular pacing rate.

[0035] If the atrial sensed rate can no longer be determined from the sensed signal picked up by using the receiving device or if the atrial sensed rate is no longer suitable for controlling ventricular pacing, pacing with the atrial sensed signal cannot or should not be applied. Typically, in leadless pacemaker devices placed in the ventricle, the atrial signal may be difficult to detect reliably because it occurs in the far-field and therefore requires, for example, electrical far-field measurements or sensing of mechanical signals, such as noise signals, acceleration signals, or pressure signals originating from a remote location. Thus, the atrial signal may be weak and, as a result, the atrial sensed rate may be lost. In addition, atrial contractions may occur too late or too early, resulting in atrial rhythm loss. If atrial contractions are too far apart, this may represent an impairment of intrinsic atrial sinus function, an episode of atrial fibrillation (which may make atrial sensing undetectable to the atrial event detection mechanism due to reduced signal amplitude), or a failure of the detection mechanism. When atrial contractions occur too early, this may represent an intrinsic conduction disorder associated with atrial tachycardia or premature atrial contractions. When the atrial rate is faster than the ventricles can reliably follow, tracking the atrial rate may result in inefficient ventricular pumping and / or ventricular fatigue, which should be avoided.

[0036] Thus, atrial tracking with adjustment of the ventricular pacing rate to the atrial sensed rate should be initiated only if the atrial sensed rate is greater than the lower limit and less than the upper limit, even if the atrial sensed rate is detectable. In this case, the ventricular pacing rate is adapted progressively to the atrial sensed rate. If this is not the case because the atrial sensed rate is less than the lower limit and therefore too small, or greater than the upper limit and therefore too large, or if the atrial sensed rate is not reliably detectable at all, the atrial tracking mode is disabled in one embodiment and no pacing is performed with the atrial sensed signal.

[0037] In this case, it may be necessary to adjust the ventricular pacing rate to a different pacing strategy, such as, for example, a rate-responsive mechanism that allows the ventricular pacing rate to vary according to the patient's physical activity. Thus, when disabling the atrial tracking mode, in one embodiment, the processing circuitry may be configured to adjust the ventricular pacing rate to synchronize the ventricular pacing rate with the pacing rate defined by the rate-responsive pacing algorithm by a predetermined second ramping function. The second ramping function may then provide a gradual adjustment of the ventricular pacing rate until it matches the pacing rate controlled and determined by the rate-responsive pacing algorithm, i.e., pacing by taking into account physical signals such as accelerometer and / or other sensor signals indicative of the patient's activity.

[0038] The second ramping function may provide linear ramping at a predetermined ramping slope, however, the second ramping function may also provide non-linear adjustment of the ventricular pacing rate.

[0039] The leadless pacemaker device can provide continuous ventricular pacing at an adaptive ventricular pacing rate. In another example, the leadless pacemaker device can be configured to provide pacing in a ventricle only if an intrinsic contraction signal in the ventricle cannot be sensed at an appropriate time. Thus, in one example, the processing circuitry is configured to generate a ventricular pacing signal when an intrinsic ventricular sensed signal is not sensed within a predetermined time window following a preceding ventricular event. Alternatively, if an intrinsic ventricular sensed signal is sensed within a predetermined time window following a preceding ventricular event over one or more cycles, no pacing signal is generated and delivered such that no pacing action is taken and the pacemaker device is in an intrinsic conduction mode that does not provide artificial pacing.

[0040] The leadless pacemaker device can comprise a housing and an array of electrodes arranged on the housing for emitting pacing signals and receiving receiving signals. The housing enables encapsulation of the leadless pacemaker device, in which the leadless pacemaker device contains all components required for autonomous operation, such as processing circuitry, energy storage such as a battery, and electrical and electronic circuitry. The housing is fluid-tight, which enables the leadless pacemaker device to be implanted in cardiac tissue and to remain there for extended periods of time to provide continuous cardiac pacing operation.

[0041] In one aspect, the electrode array includes a first electrode configured to be positioned near a distal end of the housing, the first electrode being adapted to reside in the cardiac tissue with the pacemaker device implanted such that the first electrode contacts the cardiac tissue at a location effective to introduce a stimulation signal into the cardiac tissue to induce a pacing action, specifically ventricular pacing.

[0042] In one aspect, the electrode array comprises a second electrode formed of an electrode ring extending circumferentially around the housing. Alternatively, the second electrode may be formed of, for example, a patch or another conductive area formed on the housing. The second electrode is spaced apart from the tip of the housing and thus from the first electrode arranged at the tip.

[0043] In one embodiment, the housing has a distal end opposite the tip and the electrode array has a third electrode disposed on the housing at the distal end opposite the tip, the third electrode operably connected to a processing circuit such that the processing circuit is capable of receiving and processing signals received via the third electrode.

[0044] In one aspect, the processing circuit is configured to process a sensed signal between the first or second electrode and the third electrode as a received signal indicative of atrial activity. Such a signal vector occurring between the first or second electrode and the third electrode may be referred to as a far-field vector. The first or second electrode and the third electrode exhibit a fairly long distance relative to each other, such that a far-field differential signal may be picked up with a reasonable signal-to-noise ratio.

[0045] According to one embodiment of the present invention, atrial events (As) and ventricular events (Vs) are sensed via at least two of the first electrode, the second electrode, or the third electrode.

[0046] Receiving the atrial signal may be by electrical measurement using electrodes of the electrode array, such electrodes thus forming part of a receiving device for receiving the electrical signal. Alternatively or additionally, the receiving device may include a pressure sensor, a force sensor, a motion sensor or a noise sensor for sensing a signal indicative of atrial activity. In such cases, atrial activity is not detected based on electrical measurements but is picked up by a mechanically generated signal.

[0047] Objectives are also addressed by a method of operating a leadless pacemaker device configured to provide intracardiac pacing comprising generating, using a processing circuit, a ventricular pacing signal that stimulates ventricular activity; and receiving, using a receiving device, a sensed signal indicative of atrial activity. If a valid atrial sense rate is determined, determining a ventricular pacing rate according to the atrial sensed rate based on the calculated atrial-ventricular (AV) delay; generating a ventricular pacing signal at the ventricular pacing rate; determining a calculated ventricular-atrial delay (VAcalc) indicative of a predicted time delay between a preceding ventricular event (Vs) and an atrial event (As); measuring a true occurrence of a time delay between a preceding ventricular event (Vs) and an atrial event (As) (VAtrue) and determining a correction value (CV) based on a timing relationship between the true occurrence of a time delay between a preceding ventricular event (Vs) and an atrial event (As) (VAtrue) and a calculated ventricular-atrial delay (VAcalc); adjusting the ventricular pacing rate based on a correction value (CV).

[0048] The benefits and advantageous embodiments described above for the leadless pacemaker device, as noted above, apply equally to the method.

[0049] The various features and advantages of this invention can be more readily understood with reference to the following detailed description and the illustrative embodiments illustrated in the drawings. [Brief description of the drawings]

[0050] [Figure 1] 1 is a schematic diagram of the human heart. [Diagram 2] FIG. 1 is a schematic diagram of a leadless pacemaker device. [Diagram 3]Schematic diagram of a leadless pacemaker device showing signal vectors between different electrodes of the leadless pacemaker device. [Figure 4A] 1 is a graph of an intracardiac electrogram (IEGM). [Figure 4B] FIG. 1 is a sequence diagram of an atrial sense and ventricular pace. [Diagram 5] FIG. 2 is a portion of an intracardiac electrogram illustrating modulation of ventricular rate by atrial sensed rate. [Figure 6] FIG. 10 is a schematic diagram of the adjustment mechanism for adjusting the ventricular pacing rate. [Figure 7] Figure 2. Adjustment of ventricular rate when switching between different pacing modes. [Figure 8A] FIG. 2 is an intracardiac electrogram before processing. [Figure 8B] FIG. 1 illustrates a processed signal stream derived from an intracardiac electrogram to derive atrial events. [Figure 9] FIG. 13 is a diagram of a portion of a processed signal for determining a characteristic value from the signal for determining an atrial event. [Figure 10] FIG. 13 illustrates the establishment of a window around a calculated ventricular-atrial delay to determine whether the ventricular rate is synchronized with the atrial sensed rate. [Figure 11] 1 is a flow diagram of switching between different modes of a pacemaker device. [Figure 12] 1 is a flow diagram of switching from a synchronous mode to an asynchronous mode. [Figure 13] 1 is a flow diagram of switching from an asynchronous mode to a synchronous mode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] Next, embodiments of the present invention will be described in detail with reference to the drawings, in which like reference numbers indicate like structural elements.

[0052] It should be noted that the examples do not limit the invention but merely represent illustrative examples.

[0053] The present invention proposes to provide a leadless pacemaker device for intracardiac pacing, specifically ventricular pacing.

[0054] FIG. 1 shows, in a schematic diagram, the human heart, including the right atrium (RA), right ventricle (RV), left atrium (LA), and left ventricle (LV), with the so-called sinoatrial node (SAN) located in the wall of the right atrium (RA), which is formed by a group of cells capable of spontaneously generating electrical impulses that travel through the electrical conduction system of the heart, thereby causing the heart to contract in order to pump blood through the heart. The atrioventricular node (AVN), which serves to regulate electrical conduction between the atria and the ventricles, is located in the lower posterior part of the intraatrial septum, near the opening of the coronary sinus. Extending from the atrioventricular node AVN is the so-called HIS bundle H, which is made up of cardiac muscle cells specialized for electrical conduction and forms part of an electrical conduction system for transmitting electrical impulses from the atrioventricular node AVN via the so-called right bundle branch RBB around the right ventricle RV and via the left bundle branch LBB around the left ventricle LV.

[0055] When there is a block in the atrioventricular node AVN, the intrinsic electrical conduction system of the heart H may be disrupted, leading to insufficient intrinsic stimulation of ventricular activity, i.e., insufficient or irregular contractions of the right ventricle RV and / or left ventricle LV. In such cases, pacing of the ventricular activity may be required by a pacemaker device, which stimulates ventricular activity by introducing stimulation energy into the intracardiac tissue, specifically the myocardium M.

[0056] Within this document we propose the use of a leadless cardiac pacemaker device 1, shown schematic in Figure 1, to provide ventricular pacing operation.

[0057] Typical leadless pacemaker devices are designed to sense ventricular activity by receiving electrical signals from the ventricle in which the device is located, the RV, or LV, and therefore it may be desirable to provide a pacing action that achieves atrioventricular (AV) synchrony by delivering pacing in the ventricle synchronous with intrinsic atrial activity. Such a pacing mode, also referred to as atrial tracking, requires sensing atrial activity and identifying atrial events associated with atrial contractions in order to pace the ventricles based on such atrial events.

[0058] 2 and 3 , in one embodiment a leadless pacemaker device 1 configured specifically for providing intracardiac pacing using atrial tracking comprises a housing 10 housing electrical and electronic components for operating the leadless pacemaker device 1. Housing 10 specifically houses processing circuitry 15, which also has a communication interface for communicating with an external device, e.g. a programmer wand. In addition, housing 10 houses electrical and electronic components, such as an energy store in the form of a battery. Housing 10 allows encapsulation of the components housed therein, housing 10 being, for example, in the shape of a cylindrical shaft, e.g., a few centimeters in length.

[0059] The leadless pacemaker device 1 is to be initially implanted in intracardiac tissue M. For this purpose the leadless pacemaker device 1 comprises an anchoring device 14, e.g. in the form of a Nitinol wire, in the region of the distal tip 100 for engaging intracardiac tissue M and holding the leadless pacemaker device 1 firmly therein in the implanted state.

[0060] The leadless pacemaker device 1 does not include leads, but in the illustrated embodiment receives signals related to cardiac activity and emits stimulation signals through an electrode array arranged on a housing 10. In the embodiment of FIGURES 2 and 3, the leadless pacemaker device 1 has distinct electrodes 11, 12, 13 that form an electrode array and serve to emit pacing signals towards intracardiac tissue M to provide pacing, and to sense electrical signals indicative of cardiac activity, in particular atrial and ventricular contractions.

[0061] The first electrode 11 is herein designated as a pacing electrode. The first electrode 11 is disposed at a distal end 100 of the housing 10 and is configured to engage tissue M of the heart.

[0062] The second electrode 12 acts as a counter electrode to the first electrode 11, and the signal vector P arising between the first electrode 11 and the second electrode 12 provides a pacing vector that radiates a pacing signal towards the intracardiac tissue M.

[0063] In addition, the second electrode 12 can specifically act as a sensing electrode for sensing signals related to ventricular contraction, and a signal vector V arises between the second electrode 12 and the first electrode 11, and the signal vector V is referred to as the near-field vector.

[0064] The second electrode 12 is disposed away from the first electrode 11 and is, for example, in the shape of a ring extending circumferentially around the housing 10. The second electrode 12 is disposed, for example, at a distance of about 1 cm from the tip 100 of the housing 10 at which the first electrode 11 is disposed.

[0065] Additionally, the leadless pacemaker device 1, in the embodiment of FIGUREs 2 and 3, comprises a third electrode 13 disposed at the distal end 101 of the housing 10 that acts as a sensing electrode for sensing signals indicative of cardiac activity in the far field. Signal vector A specifically arises between the third electrode 13 and the first electrode 11, where signal vector A picks up signals indicative of, for example, atrial contractions and is referred to as a far-field vector.

[0066] The electrodes 11, 12, 13 are operatively connected to a processing circuit 15 configured to cause the first electrode 11 and the second electrode 12 to emit pacing signals that provide stimulation at the ventricles. The processing circuit 15 is further configured to process signals received via the electrodes 11, 12, 13 to provide sensing of cardiac activity, in particular atrial and ventricular contractions.

[0067] To provide pacing in the ventricle in which the leadless pacemaker device 1 is placed, and in particular to enable pacing using atrial tracking, sensing of atrial activity is required to provide atrial sense markers that are detected to time pacing in the ventricle in atrioventricular (AV) synchrony. For this purpose, specifically right atrial RA (see Fig. 1 ) far-field signals should be sensed to enable synchronous pacing in the right ventricle RV by implanting the leadless pacemaker device 1 in endocardial tissue M in the right ventricle RV.

[0068] In general, when a component sinus rhythm is available, it is preferable to use such sinus rhythm to time ventricular pacing based on the sinus rhythm. However, because the pacemaker device 1 is placed in the ventricle, signals enabling detection of an atrial sensed rate indicative of intrinsic atrial activity are not always reliably possible because the amplitude of the received signal may be low. In addition, pacing in the ventricle based on and synchronous with the atrial signal may not be appropriate if the detected atrial sensed rate is too slow or too fast. If atrial events detected based on signals received from the atrium are too far apart, this may represent a disturbance in intrinsic atrial sinus function, an episode of atrial fibrillation, or a disturbance in the detection mechanism. In contrast, if atrial events are too close together, this may represent an intrinsic conduction disturbance associated with atrial tachycardia or atrial premature beats, in which case the atrial sensed rate may be too fast for the ventricle and atrial tracking should be avoided to avoid inefficient ventricular pumping or ventricular fatigue.

[0069] Thus, it may be necessary to switch between an atrial tracking mode and a mode in which atrial tracking is disabled. In the atrial tracking mode, pacing in the ventricle is performed based on the detected atrial sensed rate. In contrast, when the atrial tracking mode is disabled, ventricular pacing is performed by utilizing another mechanism, such as a rate-responsive mechanism, in which the ventricular pacing rate is governed by and varies in response to the patient's detected physical activity, which may be derived from sensor readings, such as accelerometer readings, for example.

[0070] In general, the atrial tracking mode should be disabled if the atrial sensed rate is too small or too large (i.e., the atrial sensed rate is less than the lower limit or greater than the upper limit) or if a reliable atrial sensed rate cannot be derived from the atrial signal. Alternatively, if the atrial sensed rate can be reliably detected because atrial events are being continuously received and a stable atrial rate can be determined, and, in addition, if the atrial sensed rate is between the lower and upper limits, the atrial tracking mode should be enabled.

[0071] When an atrial tracking mode is enabled, the ventricular pacing rate should be adapted to the atrial sensed rate, where prior to enabling the atrial tracking mode, the ventricular pacing rate was controlled according to another mechanism and may therefore be significantly different from the currently available atrial sensed rate, and as a result, enabling the atrial tracking mode now involves controlling the ventricular pacing rate to account for the atrial sensed rate.

[0072] To avoid an abrupt switch from one ventricular pacing rate to another when activating an atrial tracking mode, it is proposed herein to gradually adjust the ventricular pacing rate so that it is gradually adapted to resemble and follow the atrial sensed rate. The gradual adjustment can take into account programmed attack and decay limits so that the slope of the adaptation of the ventricular pacing rate does not exceed predefined limits.

[0073] In one embodiment, the adjustment of the ventricular pacing rate towards the currently available atrial sensed rate can follow the principle of a phase-locked loop, where the control mechanism is such that a correction value is determined according to the difference between the phase of the atrial sensed rate and the current ventricular pacing rate, and the correction value is then used to correct the ventricular pacing rate so that it is adjusted towards the atrial sensed rate.

[0074] In one embodiment, when switching to an atrial tracking mode, an (ideal) atrial-ventricular delay AV is determined, as shown in FIG. 4A with an example of an intracardiac electrogram IEGM. The calculation of the atrial-ventricular delay AV can, for example, utilize an average of an atrial interval TA between two successive atrial events As, the average being measured, for example, over multiple cycles. The average atrial-ventricular delay AV, together with a current interval TV of ventricular pacing, can then be used to calculate a ventricular-atrial delay VA indicating the predicted time at which an atrial event As should follow a ventricular paced or sensed event Vs (if the ventricular paced rate and the atrial sensed rate are synchronous).

[0075] FIG. 4B illustrates a schematic of a sequence 41 of atrial sensed events As and a sequence 42 of ventricular paced events Vp following the atrial sensed events. According to one aspect of the invention, the ventricular pacing rate can be changed to match the atrial sensed rate. The atrial pacing rate in sequence 41 of FIG. 4B is 60 bpm due to an interatrial interval of 1000 ms. The phase relationship between the paced interval and the atrial interval can be adjusted by changing the ventricular pacing rate by a small amount within one cardiac cycle and then returning it to the previous rate in the next cycle. For example, if the atrial rate is 60 bpm as in sequence 41 and the ventricular pacing rate is 60 ppm, the duration between the atrial sense and the ventricular pace can be, for example, 180 ms (43 in FIG. 4B). If it were desired to adjust the AV delay to 200 ms instead, one could generate a longer interventricular pacing interval for one cycle (44 in FIG. 4B) to achieve a temporal shift in Vp relative to As, and then set the interventricular pacing interval back to 1000 ms (cycle 45 in FIG. 4B). If the AV delay is measured every cycle and compared to the desired delay, such small corrections can be used to continually keep the AV delay at the appropriate value, even as the atrial rate drifts up and down. A side effect is that the ventricular rate will track any drift in the atrial rate.

[0076] Calculate ventricular-atrial delay VA as shown in Figure 5 calc A correction of the ventricular pacing rate can be performed based on, and based on a measurement of the true time of occurrence of the next atrial event As following a ventricular paced or sensed event Vs.

[0077] In particular, at the time of a ventricular event Vx (which may be a paced event Vp or an intrinsic ventricular sensed event Vs), a timer is started. At the time of the next atrial event As, the timer time TT is stored, thereby obtaining the true time of occurrence of the atrial event As that follows the preceding ventricular event Vs.

[0078] Here, the true occurrence time of the atrial event As is calculated as the ventricular-atrial delay VA. calc and from such comparison, a correction value can be determined.

[0079] In particular, in one embodiment, as shown in FIG. -3 ...B +2 and time bin B can be defined. -3 ...B +2 The central time bin B0 calculates the ventricular-atrial delay VA calc , i.e., the predicted occurrence time of an atrial event As when the ventricular rate and the atrial sensed rate are synchronized, is calculated as the ventricular-atrial delay VA. calc are distributed around

[0080] Here, for each time bin B -3 ...B +2 is bounded by lower limits L1...L6 and upper limits L2...L7, and time bin B -3 ...B +2 For example, have the same width.

[0081] Each time bin B -3 ...B +2 is associated with a particular setpoint. The central time bin B0 has a setpoint of 0. The time bins B -3 ...B -1 has a positive set value, while the time bins B +1 , B +2 has a negative set value.

[0082] Based on the measured true occurrence time of the atrial event A, the time bin B in which the atrial event A falls is determined. -3 ...B +2 Then, the corresponding time bin B -3 ...B +2Therefore, if the atrial event As falls in the central time bin B0, the correction value is set to 0. If the atrial event As falls in the time bin B0 preceding the central time bin B0, the correction value is set to 0. -3 ...B -1 If the true occurrence time of the atrial event As falls in time bin B, the correction value is -3 ...B -1 is set to a positive value according to a specific setting of time bin B -3 ...B -1 The setting value is for time bin B -3 ...B -1 increases gradually as it moves away from the central time bin B0. +1 , B +2 If the true occurrence time of the atrial event As falls in time bin B, the correction value is +1 , B +2 is set to a negative value according to a specific setting value of time bin B. +1 , B +2 The magnitude of the setting value is also in this case for time bin B. +1 , B +2 increases with distance from the central time bin B0.

[0083] A positive offset increases the ventricular pacing rate, resulting in ventricular pacing at a faster rate. A negative offset decreases the ventricular pacing rate, resulting in slower ventricular pacing. In this example, the offset is calculated based on the true occurrence time of an atrial event As (which follows a preceding ventricular event Vs) and its predicted occurrence time (calculated ventricular-atrial delay VA). calc Since the ventricular pacing rate is set incrementally based on the difference between the ventricular rate and the atrial sensed rate, as determined by a comparison with the atrial sensed rate (represented by α, β ...

[0084] The principle of ventricular pacing rate adjustment when enabling an atrial tracking mode (and similarly when disabling an atrial tracking mode and switching to another pacing mode) can be compared to a phase-locked loop technique, as generally shown in Figure 6.

[0085] In such a technique, an input I, i.e. in this case the atrial sensed rate, is compared in a comparator 150 with an output rate O, i.e. in this case the ventricular pacing rate. The comparator 150 determines, inter alia, the phase difference between the input rate I, i.e. the atrial sensed rate, and the output rate O, i.e. the ventricular pacing rate, and provides this difference towards a filtering unit 151, which may enable filtering in order to improve the stability of the control mechanism. The filtered difference is then forwarded to an adjustment unit 152, which determines a correction value for correcting the output rate O, i.e. the ventricular pacing rate, according to the difference and adjusts the output rate O accordingly. The now corrected output rate O, i.e. the ventricular pacing rate, is fed back to the input, so that a feedback mechanism is provided for progressively adjusting the output rate O, i.e. the ventricular pacing rate, according to the input rate I, i.e. the atrial sensed rate.

[0086] Thus, adjustments to the ventricular pacing rate are made according to predefined attack and decay limits on the rate of change such that changes in the ventricular pacing rate are made gradually, as illustrated in FIG.

[0087] Here, prior to time T1, the ventricular pacing rate is controlled according to a pacing mechanism other than atrial tracking. The ventricular pacing rate may be controlled according to a rate-responsive mechanism, for example, in which the ventricular pacing rate is varied according to the patient's physical activity to relative the rate-responsive rate FR, such that the ventricular pacing rate is reduced during times of inactivity, e.g., during sleep, and increased during times of intense activity, e.g., during vigorous physical exercise.

[0088] Prior to time T1, there is no atrial sensed rate available or suitable for pacing. At time T1, a suitable atrial sensed rate FA becomes available, so that the pacemaker device 1 switches to an atrial tracking mode in which the ventricular pacing rate is controlled according to the detected atrial sensed rate FA.

[0089] Here, in a first phase between times T1 and T2, the ventricular pacing rate is ramped up according to a ramping function R1 until it is synchronized with the atrial sensed rate FA at time T2, and from that point on, is controlled in synchronization with the atrial sensed rate FA. The ramping function R1 is defined by progressively adjusting the ventricular rate using iterative application of appropriate correction values ​​as described above for one embodiment.

[0090] At time T3, an appropriate atrial sensed rate is no longer available due to a decrease in sensed atrial signal or because the atrial sensed rate has become too small or too high. The pacemaker device 1 then switches back to another pacing mode, such as a pacing mode utilizing a rate-responsive mechanism. Again, to avoid an abrupt switch in the ventricular pacing rate, the ventricular pacing rate is adapted gradually by applying a ramping function R2 until it converges towards the rate-responsive rate FR.

[0091] For switching back to the cardiac response rate FR, a similar mechanism to switching to synchronize with the atrial sensed rate may be applied.

[0092] The ventricular pacing may be continuous, such that a pacing signal is generated and delivered to the cardiac tissue independent of intrinsic ventricular activity. Alternatively, an intrinsic signal may be sensed and taken into account to avoid ventricular pacing when an intrinsic ventricular signal is present. For this purpose, at each ventricular event Vs, there may be a ventricular paced event or a ventricular sensed event due to intrinsic ventricular activity, and a ventricular pacing rate timer may be started, the timer defining the maximum time by which an intrinsic ventricular event must occur to avoid a ventricular pacing signal. If the timer has not expired when an intrinsic ventricular event Vs is detected, the generation of the ventricular pacing signal is skipped. If the timer expires, a ventricular pacing signal is generated and delivered.

[0093] 2 and 3, a far-field vector between the electrodes 11, 13 that are furthest on the housing 10 of the pacemaker device 1 is beneficially used to detect atrial signals to derive an atrial sensed rate. Such a large vector is preferred to accentuate variations in the electromagnetic field paths from the right atrial tissue to the electrodes 11, 13, allowing detection of differential signals indicative of atrial activity.

[0094] The measured signals should be filtered to distinguish atrial signals from other signals, especially ventricular signals, and in addition, a blanking mechanism can be utilized to blank out signals not related to atrial activity.

[0095] This is illustrated in Figures 8A and 8B, which show, in one example, the intracardiac electrogram IEGM measured in the ventricle before filtering and blanking (Figure 8A) and after filtering and blanking (Figure 8B). In particular, the blanking window T blank can be used to blank out such periods of signal that may be related to activity in the heart other than atrial activity.

[0096] The processed and filtered signal is then used to determine atrial events As.

[0097] The atrial events As can be determined, inter alia, by utilizing a processor or state machine logic. In particular, to determine the atrial events Vs, the signal can be analyzed to determine the maximum positive peak PP, the maximum negative peak PN, the average value AP of the positive signal portion above a criterion B, and the average value AN of the negative portion below a criterion B, as shown in FIG. 9. The atrial events As can then be determined, for example, according to the crossing of a threshold D, and one or more thresholds can be utilized, for example, a positive threshold and a negative threshold, the thresholds being calculated, for example, according to characteristics determined from the processed signals.

[0098] Generally, on the other hand, if intrinsic ventricular activity is present, beneficially such intrinsic signals should not be interrupted by artificial pacing, depending on whether the intrinsic ventricular activity is synchronous with the atrial activity. If synchronous intrinsic ventricular activity is present, the pacemaker device 1 should be operated in an intrinsic conduction mode in which the heart operates naturally utilizing its intrinsic conduction mechanisms.

[0099] In the intrinsic conduction mode, the pacemaker device 1 specifically monitors the ventricular activity synchronized with the atrial activity. For this purpose, time windows W1, W2 as shown in Fig. 10 can be established to monitor the duration between a ventricular event Vs and a subsequent atrial event As.

[0100] Here, the windows W1 and W2 are the calculated ventricular-atrial delay VA as referenced above. calc (See in particular Figures 4 and 5 and the corresponding description) based on which the calculated ventricular-atrial delay VA calc indicates the time at which an atrial event As should follow a preceding ventricular event Vs if the ventricular and atrial rates are synchronous.

[0101] Windows W1 and W2 are specifically the ventricular-atrial delay VA calc At each intrinsic ventricular event Vs, a timer is started and the true time of occurrence of the atrial event As (timer time TT) is determined and stored. If the true time of occurrence of the atrial event As falls within the inner window W1, the ventricular and atrial rates are assumed to be synchronous and the pacemaker device remains in the intrinsic conduction mode and therefore does not provide any artificial pacing.

[0102] Instead, if the true occurrence time of an atrial event As falls outside the inner window W1 but still falls within the outer wider window W2 (also called the drift window), then it is assumed that atrioventricular synchrony is lost. Thus, the processing circuitry 15 of the pacemaker device 1 switches to an atrial tracking mode and controls the ventricular rate by generating and introducing a pacing signal. To adjust the ventricular pacing rate relative to the atrial sensed rate, an algorithm such as that described above according to FIG. 5 may now be utilized, thus adjusting the ventricular pacing rate in a manner similar to a phase-locked loop control.

[0103] When a predetermined number of consecutive ventricular senses occur synchronously with the atrial rate, the control logic can switch back to the intrinsic conduction mode.

[0104] If an atrial event As does not occur within windows W1, W2, the control logic of processing circuitry 15 may switch to a search mode in which an atrial event As is searched for. Within such a search mode, the ventricular rate may be controlled according to another pacing mechanism, such as a rate-responsive mechanism, and the ventricular pacing rate may be progressively adjusted to approach the rate controlled by the rate-responsive mechanism.

[0105] A search for an atrial event As is initiated when the processing circuitry 15 is in a search mode. In the search mode, the processing circuitry 15 may analyze the intracardiac electrogram readings for possible atrial events and may determine characteristic values ​​such as peak and average values ​​to evaluate possible candidates for atrial events. Bandpass filters may be utilized to cover the frequency range of supported atrial sensing, and the frequencies may be sorted into a contiguous range of filter bins. The digital data stream analyzed by the processing circuitry may be fed into such filter bins, and at the output of each filter (except for the filter covering the current ventricular rate and the corresponding heartbeat interval), a threshold detector may be enabled. The threshold utilized by the threshold detector may be a general value that may be controlled by the search algorithm. Here, the threshold may be raised or lowered until only one detector is active during a predetermined number of consecutive ventricular cycles. The interval associated with this detector is used to reload a ventricular timer at each ventricular event Vs. This results in a calculated ventricular-atrial delay VA. calc If a stable candidate atrial event is obtained within the time period, it is now assumed that the atrial sensed rate is picked up again, and the control logic can switch back to the intrinsic conduction mode or atrial tracking mode. In contrast, the calculated ventricular-atrial delay VA calc If no stable candidate atrial event As is detected within the period, the search circuitry can be disabled to conserve power, e.g., pacing continues according to a rate-responsive mechanism.

[0106] If the search is not successful in identifying a stable atrial event As, a predetermined search delay can be initiated to temporarily stop the search. The control logic can use an adaptive rate via the rate response mechanism to reload the ventricular timer during the search delay, and at the end of the search delay, re-enable the search circuitry to perform another search. This can be repeated indefinitely as long as a stable candidate atrial event As is not detected, and therefore a reliable atrial sensing rate is not picked up.

[0107] Between searches, the control logic may monitor for consistent candidate atrial events As within a ventricular-atrial delay window (window W1 in FIG. 10), and if a stable atrial event As is detected, the control logic switches back to the intrinsic conduction mode.

[0108] Switching between different modes according to one embodiment is shown in FIG. 11. When an atrial sensed rate is detected and synchronized with the ventricular rate of an intrinsic ventricular event Vs, the pacemaker device 1 is in an intrinsic conduction mode S1. If synchronization is lost because the ventricular and atrial rates are out of sync, the pacemaker device 1 switches to a tracking mode S2. If a stable atrial sense is not available that allows detection of an atrial sensed rate in either the intrinsic conduction mode S1 or the tracking mode S2, the device switches to a search mode S3. If a search is performed but is not successful in identifying a stable atrial event As, the device can switch to a delay mode S4 where the search is stopped and the search circuitry is powered down to conserve energy until the end of the search delay when the device switches back to search mode S3. If a reliable atrial sensed rate that is synchronized with the ventricular rate is again detected, the device switches back to intrinsic conduction mode S1 (or switches to tracking mode S2 if the atrial sensed rate is not synchronized with the ventricular rate).

[0109] A general schematic of switching between atrioventricular synchronous mode with atrial tracking and asynchronous mode is shown in FIGS.

[0110] In synchronous mode, atrial tracking is utilized, so that the ventricular pacing rate follows the intrinsic atrial sensed rate. In synchronous mode (state N1 in FIG. 12), if an atrial feature is detected and therefore the atrial sensed rate is reliably picked up, the device remains in synchronous mode (state N2). Alternatively, if an atrial event As is not detected for a predefined number of cycles N, e.g., 10 consecutive cycles, the device will continue to synchronous mode (state N3). asynchIt is possible to check whether an atrial event As can be detected over a predetermined number of cycles N. asynch If no atrial event As can be detected for a given number of consecutive cycles N in state N3, the pacing mode is switched to an asynchronous pacing mode (state N4). asynch If the atrial event As is picked up again before A s reaches A s , the device remains in synchronous mode (state N5).

[0111] If the device is in asynchronous mode (state M1 as shown in FIG. 13), it is checked whether the atrial feature As is detected. If this is the case, the atrial feature As is detected for a predetermined number of cycles N, e.g., 10 cycles. synch It can be checked (state M2) whether atrial events As can be stably detected over a period of time. If this is the case, a switch to synchronous mode is made (state M3).

[0112] If no atrial features are detected in state M1, the device remains in the asynchronous pacing mode (state M4). synch If no stable atrial events As can be detected over a period of time, the device also remains in asynchronous pacing mode (state M5).

[0113] A predetermined number of periods N for switching to asynchronous mode (state N3 in FIG. 12) asynch and a predetermined number of periods N for switching from the asynchronous mode to the synchronous mode (state M2 in FIG. 13). synch may be equal to or different from each other. asynch , N synch may be, for example, 10, but may also be larger or smaller.

[0114] Algorithms and procedures for controlling the pacing rate and switching from one mode to another are implemented in the processing circuitry 15 of the pacemaker device 1, for example, by software running on one or more suitable processors.

[0115] Numerous modifications and variations of the described examples and embodiments will be apparent to those skilled in the art in light of the above teachings. The disclosed examples and embodiments are presented for illustrative purposes only. Other alternative embodiments may incorporate some or all of the features disclosed herein. It is therefore intended to cover all such modifications and alternative embodiments that may fall within the true scope of this invention. [Explanation of symbols]

[0116] 1 Leadless pacemaker device 10. Chassis 100 Tip 101 Far end 11 First electrode (pacing electrode) 12 Second electrode (pacing ring) 13 Third electrode 14 Fixation Devices 15 Processing circuit 150 Comparator 151 Filter Processing Unit 152 Adjustment Unit A Atrial vector AN Negative Average Value AP Positive Mean As Atrial Event AV Atrial-Ventricular Delay AVN Atrioventricular Node B criteria B0, B -1 , B -2 , B -3 , B +1 , B +2 Time Bins CV correction value D. Threshold FA Atrial Rate FR Heart Rate Response Rate FV Ventricular rate H HIS bunch L1~L7 limits LA Left atrium LBB left leg LV left ventricle M: Cardiac tissue (myocardium) P pacing vector PN Negative peak value PP Positive peak value R1, R2 ramping functions RA right atrium RBB right leg RV right ventricle S1~S4 Mode T1~T4 time TA Atrial Interval TV Ventricular Interval T blank Blanking Window TT Timer time SAN sinoatrial node V ventricular vector VA Ventricular-Atrial Delay VA calc Calculate ventricular-atrial delay Vs Ventricular Events W1, W2 windows

Claims

1. A leadless pacemaker device (1) configured to provide intracardiac pacing, comprising: a processing circuit (15) configured to generate a ventricular pacing signal for stimulating the ventricle; a receiving device for receiving sensed signals indicative of atrial activity, the processing circuit (15) being configured to detect atrial events (As) derived from the sensed signals, the atrial events being valid atrial sensed events if a series of atrial events is within a range of normal atrial rates and / or if the variability of the atrial rate is within a certain range indicative of a normal atrial rhythm; If a valid atrial sensed event is detected, the processing circuitry (15) determining an atrial-ventricular (AV) delay indicative of a time delay between an atrial event and a predicted occurrence of a ventricular paced or sensed event; determining a ventricular pacing timing of a ventricular pacing event following the atrial event based on the atrio-ventricular (AV) delay; A calculated ventricular-atrial delay (VA) indicating the time delay that a further atrial event (As) is expected to occur following the ventricular paced or sensed event (Vs). ｃａｌｃ ) and The true occurrence (VA) of the time delay following the ventricular paced or sensed event (Vs) at which the further atrial event (As) occurs. ｔｒｕｅ ) was measured, and VA ｔｒｕｅ and the calculated ventricular-atrial delay (VA ｃａｌｃ determining a correction value (CV) based on a timing relationship between the adjusting the ventricular pacing timing based on the correction value (CV); The leadless pacemaker device (1), further configured to:

2. 2. The leadless pacemaker device of claim 1, wherein the processing circuitry is configured to determine a ventricular pacing event based on a calculated ventricular pacing event if a valid atrial sensed event is not detected.

3. The processing circuit (15) determines the calculated ventricular-atrial delay (VA) based on a calculated atrial-ventricular delay (AV) and a current ventricular interval (TV) indicative of the time interval between two successive ventricular pacing signals. ｃａｌｃ The leadless pacemaker device (1) of claim 1 or 2 configured to determine a .times. ...

4. The processing circuit (15) processes a plurality of time bins (B ０ , B －１ , B －２ , B －３ , B ＋１ , B ＋２ ) is determined, and VA is used to determine the correction value (CV). ｔｒｕｅ Which time bin (B ０ , B －１ , B －２ , B －３ , B ＋１ , B ＋２ The leadless pacemaker device (1) of any one of claims 1 to 3 configured to evaluate whether a certain period of time passes before a certain point of time passes.

5. Each time bin (B ０ , B －１ , B －２ , B －３ , B ＋１ , B ＋２ 5. The leadless pacemaker device of claim 4 , wherein the time interval (T1) is defined by a lower and an upper time limit.

6. Each time bin (B ０ , B －１ , B －２ , B －３ , B ＋１ , B ＋２ ) is associated with a particular set value, and the processing circuit (15) ｔｒｕｅ The time bin (B ０ , B －１ , B －２ , B －３ , B ＋１ , B ＋２ 5. The leadless pacemaker device (1) of claim 4 configured to set the correction value (CV) using the set value of a CV_adjustment parameter (CV_adjustment).

7. The processing circuit (15) ｔｒｕｅ is the calculated ventricular-atrial delay (VA ｃａｌｃ The time bin (B ０ , B －１ , B －２ , B －３ , B ＋１ , B ＋２ ventricular pacing rate determined by multiple ventricular events when the true occurrence time falls within the calculated ventricular-atrial delay (VA). ｃａｌｃ ) at the end of the following time bin (B ０ , B －１ , B －２ , B －３ , B ＋１ , B ＋２ The leadless pacemaker device (1) of claim 4 configured to reduce the ventricular pacing rate when a cardiac arrest occurs.

8. The processing circuit (15) is configured to determine a VA delay feedback value, the VA delay feedback value being a function of the calculated ventricular-atrial delay (VA ｃａｌｃ ) and V.A. ｔｒｕｅ and the processing circuitry (15) configured to calculate the correction value (CV) based on the VA delay feedback value.

9. 8. The leadless pacemaker device of claim 7, wherein the processing circuitry is configured to adjust the ventricular pacing rate synchronously with an atrial sensed rate, determined by a plurality of atrial events, according to a first predetermined ramping function (R1) when the atrial sensed rate is suitable for pacing.

10. 10. The leadless pacemaker device of claim 9, wherein the processing circuit (15) is configured to adjust the ventricular pacing rate to be synchronous with a pacing rate defined by a rate-responsive pacing algorithm according to a second predetermined ramping function (R2) when the atrial sensed rate is not suitable for pacing.

11. 11. The leadless pacemaker device of claim 1, wherein the processing circuitry is configured to generate a ventricular pacing signal when an intrinsic ventricular sense signal is not detected within a predetermined time window following a preceding ventricular event.

12. The leadless pacemaker device (1) of any one of claims 1 to 11, wherein the receiving device comprises at least two electrodes (11-13) for receiving sensed signals indicative of atrial activity.

13. 13. The leadless pacemaker device (1) of claim 12 comprising a housing (10) having a distal end (100) and a distal end (101), with one electrode (11, 12) arranged proximate the distal end (100) and another electrode (13) arranged proximate the distal end (101).

14. 1. A method of operating a leadless pacemaker device configured to provide intracardiac pacing, comprising: generating, using a processing circuit (15), at least one ventricular pacing signal for stimulating ventricular activity; receiving, using a receiving device, a sensed signal indicative of atrial activity; detecting an atrial event (As) derived from the sensed signal, the atrial event being a valid atrial sensed event if a series of atrial sensed events is within a range of normal atrial rates and / or if the atrial rate variability is within a certain range indicative of a normal atrial rhythm; If a valid atrial sense event is detected, determining an atrial-ventricular delay indicative of a predicted time delay between an atrial event and a ventricular paced or sensed event; determining a ventricular pacing timing of a ventricular pacing event following the atrial event based on the atrio-ventricular (AV) delay; A calculated ventricular-atrial delay (VA) indicating the time delay that a further atrial event (As) is expected to occur following the ventricular paced or sensed event (Vs). ｃａｌｃ ) The true occurrence (VA) of the time delay following the ventricular paced or sensed event (Vs) at which the further atrial event (As) occurs. ｔｒｕｅ ) and determining the true occurrence of the time delay (VA) of an atrial event (As) following the ventricular paced or sensed event (Vs). ｔｒｕｅ ) and the calculated ventricular-atrial delay (VA ｃａｌｃ determining a correction value (CV) based on a timing relationship between the adjusting the ventricular pacing timing based on the correction value (CV); A method comprising:

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