A leadless cardiac pacemaker device configured to provide intracardiac pacing

Abstract

To provide a leadless pacemaker device 1 to provide an intra-cardiac pacing.SOLUTION: The leadless pacemaker device 1 includes processing circuitry 15 configured to generate ventricular pacing signals for stimulating ventricular activity at a ventricular pacing rate, and a sensor configuration configured to receive a sense signal over a multiplicity of heart cycles. The processing circuitry 15 is configured to derive a combined signal portion Scomb from signal portions S of the sense signal relating to the multiplicity of heart cycles and to analyze the combined signal portion Scomb for obtaining information relating to an atrial event As. Thus, the leadless pacemaker device allows, in particular, a reliable detection of signals relating to an atrial activity and the use of such signals for controlling a ventricular pacing rate for ventricular pacing. The processing circuitry 15 is configured to sum a predefined number of signal portions S relating to different heart cycles to obtain the combined signal portion Scomb.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention generally relates to a leadless cardiac pacemaker device that provides intracardiac (intracavitary) pacing, particularly ventricular pacing.

Background Art

[0002] A leadless pacemaker avoids the use of a lead as the pacemaker device itself is implanted intracardially, as opposed to a pacemaker that is implanted subcutaneously using a lead that extends transvenously into the heart. The pacemaker is in the shape of a capsule and is implanted within cardiac tissue, specifically within the right ventricular wall of the right ventricle. Such a leadless pacemaker exhibits the inherent advantage of not using a lead and can reduce the risks to the patient associated with transvenous access of the heart with a lead, such as the risks of pneumothorax, lead dislodgement, cardiac perforation, venous thrombosis, etc.

[0003] A leadless pacemaker may be specially designed for implantation within the right ventricle, in which case, upon implantation, the pacemaker is positioned within or on the wall of the right ventricle. Ventricular pacing may be necessary, for example, when there is dysfunction at the AV node but the sinoatrial node function is normal and appropriate. In such a case, specifically, so-called VDD pacing may be desired, which requires ventricular pacing with atrial tracking and thus requires sensing of atrial activity in order to pace the ventricle based on intrinsic atrial contractions.

[0004] Pacing using atrial tracking is specifically motivated by the hemodynamic advantages of atrioventricular (AV) synchrony in patients, which is achieved by triggering ventricular pacing using appropriate sinoatrial node function, thereby maximizing ventricular preload, limiting regurgitation across the AV valve, maintaining a low mean atrial pressure, and potentially modulating autonomic and neurohumoral reflexes.

[0005] There are publications seeking solutions that use modalities for detecting mechanical events of atrial contraction, including the sensing of movement, sound, and pressure. For example, U.S. Patent Application Publication No. 2018 / 0021581A1 discloses a leadless cardiac pacemaker comprising a pressure sensor and / or an accelerometer for determining atrial contraction timing. Since mechanical events generally exhibit a small signal volume, signal detection based on mechanical events, such as movement, sound, or pressure, can be difficult, especially when the leadless pacemaker device is placed within the ventricle and thus quite far from the atrium where its contractions are to be sensed. In addition, the wall movement and blood flow caused by atrial contraction may not directly transfer to the ventricle, and hemodynamic signals of the heart, such as movement, heart sound, and pressure, may be affected by external factors such as posture and patient activity.

[0006] European Registered Patent No. 3 218 049B1 describes a leadless pacemaker device configured to be implanted within the ventricle of a patient's heart and configured to switch from an atrioventricular synchronous pacing mode to an asynchronous pacing mode in response to the detection of one or more sensed ventricular events.

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

[0008] Signals related to atrial activity are inherently small when received in the ventricles. This applies to both electrical signals received by a suitable electrode array of a leadless pacemaker device and mechanical signals such as motion signals, pressure signals, or sound signals. Considering the limitations in the reception of electrical and mechanical signals, it is difficult to achieve reliable identification of atrial events that would enable pacing with atrial tracking to control the ventricular pacing rate.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0010] Specifically, an object is to provide a leadless pacemaker device and a method of operating a leadless pacemaker device that enable reliable detection of signals related to atrial activity and use such signals to control the ventricular pacing rate of ventricular pacing.

Means for Solving the Problems

[0011] A leadless cardiac pacemaker device configured to provide intracardiac pacing and having the features of claim 1, and a method according to claim 12 are provided.

[0012] In one aspect, a leadless pacemaker device configured to provide intracardiac pacing has a processing circuit configured to generate a ventricular pacing signal for stimulating ventricular activity at a ventricular pacing rate, and a sensor array configured to receive sensed signals over a number of cardiac cycles. The processing circuit is configured to derive a combined signal portion from the signal portions of the sensed signals associated with the number of cardiac cycles and to analyze the combined signal portion to obtain information related to atrial events.

[0013] Generally, signals related to atrial activity may be small when received, for example, by a leadless pacemaker device implanted within the ventricle. The sensed signals herein are generally received by electrical sensors such as electrode arrays for detecting atrial activity according to endogenous electrical signals occurring in the atrium, or by mechanical sensors such as motion sensors, pressure sensors, or sound sensors for detecting atrial activity according to mechanical events such as mechanical movement, pressure changes, or sounds due to atrial activity.

[0014] The sensed signals related to atrial events in individual cardiac cycles may hardly exceed noise and may be difficult to distinguish from noise. Therefore, it is proposed to combine the signal portions related to a plurality of cardiac cycles in order to analyze the combined signal portion obtained from the signal portions related to the plurality of cardiac cycles. In such a combined signal portion, the signal related to the actual atrial event may be prominent compared to the noise. Thereby, the atrial event may be more easily detected and distinguishable from the contributions of other signals.

[0015] The combination of the signal portions related to a plurality of cardiac cycles may specifically include the sum of the signal portions related to different cardiac cycles. By summing the signal portions related to different cardiac cycles, the contributions of such signals related to atrial activity may be added so as to reinforce each other, while the contributions of the signals related to noise may cancel each other out such that the contribution of the signal related to the actual atrial activity becomes prominent.

[0016] Combinations of signal portions related to a plurality of (e.g., consecutive) cardiac cycles can include combinations of signal portions for a predefined number of cardiac cycles, e.g., any number of cardiac cycles between 2 and 30, e.g., 8 cardiac cycles. Thus, the signal portions are summed, e.g., over a predefined number of cardiac cycles, e.g., 8 cardiac cycles, and as a result, the combined signal portion represents the sum of the signal portions related to a predefined number of consecutive cardiac cycles, e.g., 8 cardiac cycles.

[0017] Subsequently, based on the combined signal portion, an analysis for identifying atrial events can be performed by evaluating characteristic values of the combined signal portion, such as, for example, positive and / or negative peak values, positive and / or negative average values, peak widths, or threshold crossings, related to signal portions above / below a reference, respectively. Specifically, the combined signal portion can be monitored to determine whether it exceeds a (positive or negative) threshold, and as a result, it can be determined whether such a threshold crossing can identify an atrial event.

[0018] Since the combined signal portion does not relate to an actual cardiac cycle alone but includes signal portions related to a predefined number of previous cardiac cycles, the determination of atrial events based on the combined signal portion does not immediately enable a decision about a specific atrial event in the actual cardiac cycle, but at least provides an indication of the timing of atrial events and the corresponding atrial rate in a predefined number of previous cardiac cycles, thereby potentially enabling the determination of the timing of ventricular pacing signals for atrial tracking, specifically, for stimulating ventricular activity.

[0019] In one aspect, the processing circuit is configured to re-determine the combined signal portion for each cardiac cycle. Thus, for each cardiac cycle, the received signal portion of the actual cardiac cycle and the combined signal portion related to the received signal portions of several previous cardiac cycles are calculated, for example, by summing the signal portions, to obtain the combined signal portion. The summation herein can be performed on a first-in first-out basis, such that for the actual cardiac cycle, the combined signal portion is determined based on the signal portions of the actual cardiac cycle and several previous cardiac cycles. Thus, the combined signal portion of the actual cardiac cycle can be the sum represented by the following equation. [Number] Here, S comb (n) represents the combined signal portion of the n-th cardiac cycle, N is a predefined number of cardiac cycles for which combination is to be performed, and S(i) is the signal portion of a specific cardiac cycle (i.e., the actual cardiac cycle (i = n) or a previous cardiac cycle).

[0020] The combined signal portion may be analyzed as is, or may be further processed, for example, by filtering, rectifying, etc., such as by averaging.

[0021] Alternatively, the combination of signal portions may also be performed based on a moving average. For example, it is conceivable to always analyze a predetermined number of cycles (e.g., 8 cycles) and use the result until the next result becomes available. Or, the moving average can be formed by always deleting the oldest signal every one cycle and adding the latest signal to calculate S comb .

[0022] The summation may also include weighting. In this specification, for example, among the summations, the signal portion from an older cardiac cycle can obtain a smaller weight than the signal portion related to the actual cardiac cycle or a newer cardiac cycle among the previous ones.

[0023] The sensed signal obtained by the sensor array may be, for example, an intracardiac electrogram obtained by an electrode array for detecting an electrical signal, or a sensed signal obtained from a mechanical sensor. The sensed signal can be received continuously, where portions of the sensed signal can be selected to obtain signal portions related to a plurality of different cardiac cycles and atrial activity during such different cardiac cycles.

[0024] To derive signal portions related to atrial activity within a cardiac cycle, a windowing strategy can be applied. Specifically, in one aspect, the processing circuit is configured to obtain a signal portion related to a cardiac cycle based on the sensed signal and based on a time window within the cardiac cycle. The time window herein can be placed, for example, within the cardiac cycle related to a previous ventricular event, such that the time window covers a period during which an atrial event can realistically be predicted.

[0025] The processing circuit herein can be configured to adaptively set the time window of the cardiac cycle based on a previous ventricular event (e.g., identified in the sensed signal).

[0026] For example, at the occurrence of a ventricular event, a timer of a predefined length can be started. At the end of the timer, i.e., after a predefined delay time represented by the length of the timer has elapsed following the previous ventricular event, the time window is started and the signal portion of a particular cardiac cycle within the time window is obtained.

[0027] The pre-defined delay time in this specification can be adaptively determined by the processing circuit based on the actual heart rate. Generally, an atrial event can be predicted to occur at a specific timing after a previous ventricular event. Therefore, the time window for detecting an atrial event should be arranged to be centered around the predicted occurrence time of the atrial event. For example, the delay time can start at a ventricular (pacing or intrinsic sensing) event and be set to cover the ventricular repolarization phase following the ventricular event. The time window can be started at the end of this phase to collect samples related to atrial activity.

[0028] For example, when the heart rate is 60 bpm (related to a cardiac cycle interval of 1000 ms), the delay time can be set to 800 ms, and the length of the time window can be set to 200 ms (or slightly shorter). For example, when the heart rate doubles to 120 bpm (related to a cardiac cycle interval of 500 ms), the delay time can be adaptively changed to 400 ms, and the length of the time window can be set to 100 ms.

[0029] By adaptively changing the delay time and / or the length of the time window based on the actual heart rate, a time window can be realized that maintains a state centered around the (predicted) occurrence time of the atrial event. In this specification, in order to combine signal portions related to different cardiac cycles, scaling or interpolation techniques for signal portions related to time windows of different lengths can be applied to obtain signal portions with the same number of samples.

[0030] In one embodiment, the sensor array has at least two electrodes that constitute an electrode array for receiving an electrical sensing signal indicating atrial activity. In this case, the sensor array is configured to receive an electrical signal in a remote field, and it is beneficial for the two electrodes to be located as far apart from each other as possible to reliably detect the differential signal between the two electrodes related to the electrical activity of the atrium.

[0031] A leadless pacemaker device can have, for example, a housing and an array of electrodes disposed and configured on the housing for emitting pacing signals and further for receiving received signals. The housing enables encapsulation of the leadless pacemaker device, and the leadless pacemaker device includes, within the housing, all components necessary for autonomous operation, such as a processing circuit, an energy storage unit such as a battery, an electrical circuit, and an electronic circuit. The housing is fluid-tight, thereby enabling the leadless pacemaker device to be implanted within heart tissue, maintained within the heart tissue over a long period of time, and providing continuous cardiac pacing operation for a long time.

[0032] In one aspect, the electrode array has a first electrode disposed and configured in the vicinity of the tip of the housing. The first electrode will remain in contact with the heart tissue with the pacemaker device implanted, such that the first electrode is in an effective location for introducing into the heart tissue a stimulation signal for inducing a pacing operation, specifically ventricular pacing.

[0033] In one aspect, the electrode array has a second electrode formed, for example, by an electrode ring extending circumferentially around the housing. Alternatively, the second electrode may be formed, for example, by a patch or another conductive area formed on the housing. The second electrode is disposed at a distance from the tip of the housing and thus at a distance from the first electrode disposed and configured at the tip.

[0034] In one embodiment, the housing has a distal end opposite the tip, and the electrode array has a third electrode disposed and configured at the distal end of the housing opposite the tip. The third electrode is operably connected to the processing circuit, such that the processing circuit can receive and process signals received via the third electrode.

[0035] 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 that occurs between the first or second electrode and the third electrode may be referred to as a remote field vector. The first or second electrode and the third electrode exhibit a relatively long distance from each other, whereby a differential signal of the remote field can be picked up with a reasonable signal-to-noise ratio.

[0036] In one aspect, in addition to or alternatively to the electrode array, the sensor array can have at least one of a motion sensor, a pressure sensor, and a sound sensor. Thus, in addition to or alternatively to the electrical signal, mechanical signals related to the movement of the heart tissue, pressure changes in the atria and ventricles, or sounds related to atrial activity and mechanical events due to atrial activity can be sensed by the sensor array. The motion sensor can be, for example, an accelerometer that receives an acceleration signal related to the movement of the heart. The pressure sensor can have, for example, a piezo element to obtain a measurement signal indicative of the pressure in the vicinity of the leadless cardiac pacemaker. The sound sensor can be, for example, a microphone.

[0037] Generally, atrial events can be detected based on different sensed signals of different physical natures. Here, the signals of the different sensors may be processed and analyzed individually to identify the atrial event, or may be processed and analyzed in combination such that atrial activity can be derived, for example, from measurements related to the electrical signal in combination with measurements related to the mechanical signal.

[0038] A leadless pacemaker device can provide continuous ventricular pacing at an adaptive ventricular pacing rate. In another embodiment, the leadless pacemaker device can be configured to provide pacing within the ventricle only when an endogenous contraction signal within the ventricle cannot be detected at a suitable timing. Thus, in one embodiment, the processing circuit is configured to generate a ventricular pacing signal when no endogenous ventricular sensing signal is detected within a predefined time window following a previous ventricular event. Otherwise, if an endogenous ventricular sensing signal is detected within a predefined time window following a previous ventricular event over one or more cycles, the pacing signal is not generated and introduced, in which case the pacing operation is not performed and the pacemaker device enters an endogenous conduction mode without supplying artificial pacing.

[0039] In another aspect, a method of operating a leadless pacemaker device configured to provide intracardiac pacing includes generating a ventricular pacing signal using a processing circuit of the leadless pacemaker device to stimulate ventricular activity at a ventricular pacing rate, receiving sensing signals over a number of cardiac cycles using a sensor array of the leadless pacemaker device, deriving a combined signal portion from a signal portion of the sensing signals associated with the number of cardiac cycles using the processing circuit, and analyzing the combined signal portion using the processing circuit to obtain information related to atrial events.

[0040] The above-described features, advantages, and examples related to the leadless pacemaker device similarly apply to the method as well, as mentioned above.

[0041] The various features and advantages of the present invention can be more easily understood with reference to the following detailed description and the embodiments shown in the drawings.

Brief Description of the Drawings

[0042]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

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Figure 7

Figure 8

Figure 9

Best Mode for Carrying Out the Invention

[0043] Subsequently, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, like reference numerals indicate like structural elements.

[0044] It should be noted that the embodiments do not limit the present invention but merely represent exemplary examples.

[0045] In the present disclosure, it is proposed to provide a leadless pacemaker device that realizes intracardiac pacing, specifically ventricular pacing.

[0046] Figure 1 is a schematic diagram showing a human heart having a right atrium (RA), a right ventricle (RV), a left atrium (LA), and a left ventricle (LV). A so-called sinoatrial node (SAN) is located within the wall of the right atrium (RA). The sinoatrial node (SAN) is formed by a group of cells having the ability to spontaneously generate electrical impulses that travel through the heart's electrical conduction system, thereby causing the heart to contract to pump blood through the heart. The atrioventricular node (AVN) functions to regulate electrical conduction between the atria and the ventricles and is located in the lower posterior portion of the atrial septum near the opening of the coronary sinus. From the atrioventricular node (AVN), a so-called His bundle (H) extends. The His bundle (H) is composed of myocardial cells specialized for electrical conduction and forms part of the electrical conduction system for transmitting electrical impulses from the atrioventricular node (AVN) through a so-called right bundle branch (RBB) around the right ventricle (RV) and through a so-called left bundle branch (LBB) around the left ventricle (LV).

[0047] When there is a block in the atrioventricular node (AVN), the heart's intrinsic electrical conduction system may be disrupted, potentially causing inadequate intrinsic stimulation of ventricular activity, i.e., inadequate or irregular contractions of the right ventricle (RV) and / or the left ventricle (LV). In such cases, pacing of ventricular activity by a pacemaker device may be required. Such a pacemaker device stimulates ventricular activity by introducing stimulating energy into the heart tissue, specifically the myocardium (M).

[0048] In this document, the use of a leadless cardiac pacemaker device 1, schematically shown in FIG. 1, is proposed to provide ventricular pacing operation.

[0049] A typical leadless pacemaker device is designed to sense ventricular activity by receiving electrical signals from the ventricles RV, LV in which the device is placed. Therefore, it may be desirable to provide a pacing operation that achieves atrioventricular (AV) synchronization by supplying pacing in the ventricles in synchronization with endogenous atrial activity. In such a pacing mode, also called atrial tracking, it is necessary to sense atrial activity and identify atrial events related to atrial contraction in order to perform ventricular pacing based on such atrial events.

[0050] Referring now to FIGS. 2 and 3, in one embodiment, a leadless pacemaker device 1 specifically configured to provide intracardiac pacing using atrial tracking has a housing 10 that houses electrical and electronic components for operating the leadless pacemaker device 1. Specifically housed within the housing 10 is a processing circuit 15 that also has a communication interface for communicating with an external device such as, for example, a programmer wand. In addition, the housing 10 houses electrical and electronic components such as an energy storage unit in the shape of a battery. The housing 10 enables encapsulation of the components housed therein and the housing 10 is, for example, in the shape of a cylindrical capsule having a length of, for example, several centimeters.

[0051] The leadless pacemaker device 1 is to be implanted in the intracardiac tissue M. For this purpose, the leadless pacemaker device 1 has, in the region of the tip 100, a fixing device 14 in the shape of, for example, a nitinol wire, to engage with the intracardiac tissue M and firmly hold the leadless pacemaker device 1 in the implanted state to the tissue.

[0052] The leadless pacemaker device 1 does not have a lead wire, but in the illustrated embodiment, receives signals related to cardiac activity by various sensors located on or within the housing.

[0053] Specifically, the leadless pacemaker device 1 in the illustrated embodiment has an electrode array disposed on the housing 10 for receiving electrical signals and for emitting stimulation signals. In the embodiments of FIGS. 2 and 3, the leadless pacemaker device 1 has different electrodes 11, 12, 13 that constitute an electrode array and act to emit pacing signals toward the heart tissue M to provide pacing and to sense electrical signals indicative of heart activity, specifically contractions of the atria and ventricles.

[0054] The first electrode 11 of the present specification is shown as a pacing electrode. The first electrode 11 is disposed at the tip 100 of the housing 10 and is configured to engage with the heart tissue M.

[0055] The second electrode 12 acts as a counter electrode to the first electrode 11, and the signal vector P generated between the first electrode 11 and the second electrode 12 provides a pacing vector that emits a pacing signal toward the heart tissue M.

[0056] In addition, the second electrode 12 can specifically act as a sensing electrode for sensing signals related to ventricular contractions, and the signal vector V is generated between the second electrode 12 and the first electrode 11, and the signal vector V is called a near-field vector.

[0057] The second electrode 12 is disposed away from the first electrode 11 and is, for example, in a ring shape 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 where the first electrode 11 is disposed.

[0058] In addition, the leadless pacemaker device 1 has a third electrode 13 disposed at the distal end 101 of the housing 10 in the embodiments of FIGS. 2 and 3, and the third electrode 13 acts as a sensing electrode for sensing signals indicative of heart activity in a remote field. The signal vector A is specifically generated between the third electrode 13 and the first electrode 11, and the signal vector A is suitable for picking up a differential signal indicative of, for example, atrial contraction and is called a remote field vector.

[0059] The electrodes 11, 12, and 13 are operably connected to a processing circuit 15, which is configured to cause the first electrode 11 and the second electrode 12 to emit pacing signals for supplying stimulation in the ventricles. The processing circuit 15 is further configured to process the signals received via the electrodes 11, 12, 13 to achieve sensing of cardiac activity, particularly atrial and ventricular contractions.

[0060] The electrodes 11, 12, 13 constitute a sensor array for sensing electrical signals. A pair of electrodes 11, 13 that define a remote field vector A may specifically enable detection of atrial events in the electrical signals received as a differential signal between the electrodes 11 and 13.

[0061] The leadless pacemaker device 1 in the embodiments of FIGS. 2 and 3 further has sensors 16, 17, 18 in addition to or instead of the sensing electrodes described above. One sensor 16 is, for example, a motion sensor, specifically an accelerometer. Another sensor 17 is a pressure sensor, and yet another sensor 18 is a sound sensor. To enable identification of atrial events, such sensors 16, 17, 18 can receive different sensing signals, thus improving the reliability of atrial event detection and enhancing the stability of atrial tracking.

[0062] Generally, sensing signals can be acquired using any of such sensor arrays 11, 13, 16, 17, 18 to obtain and derive information related to atrial activity occurring in the atria.

[0063] Generally, to provide ventricular pacing using atrial tracking, sensing of atrial activity is necessary to achieve detection of atrial sensing markers for timing ventricular pacing in atrioventricular (AV) synchronization.

[0064] Referring to FIG. 4 here, for example, the sensing signals (e.g., intracardiac electrogram IEGM) can be obtained by the electrode arrays 11, 12, 13, specifically, by a pair of electrodes 11, 13 that define the remote field vector A, and processing can be performed to derive the atrial event As and the ventricular event Vs. The atrial event As is related to the so-called P wave of the electrogram signal, and the ventricular event Vs is derived from the so-called QRS waveform of the signal.

[0065] Generally, the ventricular event Vs occurs during the ventricular interval TV, and the atrial event As occurs during the atrial interval TA. Here, when the ventricular rate is synchronized with the atrial rate, the ventricular interval TV and the atrial interval TA (substantially) coincide. The ventricular event Vs in this specification appears with a delay, the so-called atrioventricular delay AV, following the previous atrial event As. This is because of the fact that in the intrinsic conduction mechanism of the heart, the atrium contracts before the ventricle.

[0066] As can be seen from FIG. 4, the amplitude of the QRS waveform related to the ventricular event Vs is much larger than the amplitude of the P wave related to the atrial event As. Therefore, the detection of the atrial event As generally requires signal processing including, for example, filtering, particularly band-pass filtering, rectification, and / or windowing to determine whether the atrial event As has occurred, for example, by monitoring threshold exceedance.

[0067] In one embodiment, as shown in FIG. 5, a window search strategy can be used by using an investigation window W in which the atrial event As is investigated. Specifically, an investigation window W with a predefined width and a predefined time position related to the previous ventricular event Vs can be used within the sensing signal, for example, the electrical sensing signal, and the investigation window W is centered, for example, around the calculated ventricular-atrial delay VA as shown in FIG. 4.

[0068] Ventricular-atrial delay VA represents the time following the previous ventricular event Vs, at which the next atrial event As is predicted to occur. The ventricular-atrial delay VA is calculated, for example, from the average atrial interval TA and the average atrioventricular delay AV, where a ventricular pacing or sensing event Vs occurs after the previous atrial event As. According to the ventricular-atrial delay VA, the time position of the window W is determined such that the signal portion not related to atrial activity, specifically the QRS waveform, is excluded from signal processing, whereby the larger amplitude of the signal related to cardiac activity other than atrial activity is suppressed and does not interfere with the processing of the atrial signal.

[0069] The signal sensed in this way can generally be processed as shown in FIG. 6. Specifically, it can be derived from characteristic values of the sensed signal that characterize the atrial event As, specifically the positive peak amplitude PP, the negative peak amplitude PN, the positive average value AP related to the average of the signal portion exceeding the reference B, and the negative average value AN related to the negative signal portion below the reference B. In addition, for example, the pulse width PW related to the full width at half maximum of the peak of the signal can be determined. Alternatively or additionally, frequency analysis can be performed to determine the energy content of the signal in a specific frequency band.

[0070] To determine an atrial event, for example, exceeding a threshold value D can be monitored. In this specification, for example, a positive threshold value and / or a negative threshold value can be applied, where when the signal exceeds one or both of the threshold values, an atrial event can be found. The threshold value in this specification can be adaptive. The threshold value can be determined, for example, according to other characteristic values such as the negative peak amplitude PN or the positive peak amplitude PP.

[0071] Electrical or mechanical signals related to atrial activity are essentially small when received by a leadless pacemaker device 1 disposed in the ventricle, so it may be difficult to distinguish the contribution of signals related to atrial activity from the contribution of other signals. Here, referring to FIG. 7 showing signal portions S within a time window W within eight consecutive cardiac cycles #1 to #8, the contribution of signals related to atrial activity AA in each individual cardiac cycle may hardly exceed the contribution of noise N, and thus it is impossible to simply distinguish the signals related to atrial activity AA from the contribution of noise N, for example, by applying a simple thresholding technique.

[0072] The contribution of signals related to atrial activity AA can generally be assumed to be aligned for at least a reasonable number of consecutive cardiac cycles (at least when the patient's condition does not change significantly, for example, due to physical activity). Therefore, in this specification, it is proposed to combine signal portions S related to a plurality of cardiac cycles #1 to #8 to distinguish the contribution of signals related to atrial activity AA from the contribution of other signals, specifically noise.

[0073] For combination, signal portions S over a pre-defined number of cardiac cycles, i.e., over actual cardiac cycles and a number of previous cardiac cycles, are summed to obtain a combined signal portion S as shown in FIG. 8. comb In the combined signal portion S, the contributions of signals related to atrial activity AA in the individual signal portions S related to cardiac cycles #1 to #8 are added so as to reinforce each other, while noise is assumed to be effectively canceled out, so the contribution of signals related to atrial activity AA is prominent with respect to the contribution of noise N. comb The pre-defined number of cardiac cycles can be, for example, any number between 2 and 30, for example, 8.

[0074]

[0075] Since the contribution of signals related to atrial activity AA is prominent in the combined signal portion S, comb comb the combined signal portion S combFor example, by applying a simple threshold technique, for example, the combined signal portion S comb can be analyzed to detect atrial event As by comparing it with a predefined threshold D, as shown in FIG. 8. Alternatively or additionally, any other characteristic value as shown in FIG. 6 can be determined to identify atrial event As in the combined signal portion S comb .

[0076] For analysis, herein, the combined signal portion can be filtered and / or rectified before identifying atrial event As

[0077] Since the combined signal portion S comb is not (alone) related to the actual cardiac cycle, the atrial event As identified by the combined signal portion S comb does not directly indicate the atrial event As in the actual cardiac cycle. On the contrary, the atrial activity in the actual cardiac cycle only contributes to the combined signal portion S comb . Nevertheless, since the identification of atrial event As is substantially related to taking the average of the timings of atrial event As over a number of cardiac cycles, the atrial event As thus determined from the combined signal portion S comb can be used for atrial tracking and thus can be assumed to provide a reliable indicator of atrial event As, specifically, the actual cardiac cycle and the actual atrial rate

[0078] The interrogation window W shown in FIGS. 5 and 7 is determined based on the previous ventricular event Vs such that after the previous ventricular event Vs, the interrogation window W is approximately centered on the predicted time of the atrial event. Herein, the interrogation window W can also be adaptively changed in terms of its position and the length of the interrogation window time in relation to the previous ventricular event Vs, as shown in FIG. 9

[0079] Specifically, in order to cover the time range in which atrial event As may occur, for each cardiac cycle, the timing and length of windows W1 to W3 can be individually determined and set so that windows W1 to W3 are preferably arranged within the cardiac cycle.

[0080] In the example of FIG. 9, each of windows W1 to W3 is set with respect to the previous ventricular event Vs. Specifically, each of windows W1 to W3 starts from predefined delay times T1 to T3 associated with the previous ventricular event Vs. Thus, at a specific ventricular event Vs (which can be a pacing event or an endogenous sensing event), a timer is started that coincides with delay times T1 to T3 and specifically effectively covers the ventricular repolarization phase after the previous ventricular event Vs. At the end of delay times T1 to T3, windows W1 to W3 are started, and within windows W1 to W3, signal portions related to atrial activity within a specific cardiac cycle are obtained.

[0081] When the heart rate changes, delay times T1 to T3 can be proportionally adapted according to the change in heart rate. For example, when the heart rate is initially 60 bpm (related to a cardiac interval of 1000 ms), delay times T1 to T3 can be set to 800 ms, and the window lengths of windows W1 to W3 can be set to 200 ms. For example, when the heart rate doubles to 120 bpm (related to a cardiac interval of 500 ms), delay times T1 to T3 and the window lengths of windows W1 to W3 can be proportionally adapted to 400 ms and 100 ms, respectively.

[0082] To combine signal portions related to different cardiac cycles, for example, scaling of signal portions related to different windows W1 to W3 can be performed so that sample portions with the same number of samples can be preferably summed.

[0083] In light of the above teachings, it will be apparent to those skilled in the art that numerous changes and modifications can be made to the described examples and embodiments. The disclosed examples and embodiments are presented for illustrative purposes only. Other alternative embodiments may include some or all of the features disclosed herein. Therefore, it is intended to cover all such changes and alternative embodiments that may fall within the true scope of this invention.

Explanation of Reference Signs

[0084] 1 Leadless Pacemaker Device 10 Housing 100 Tip 101 Distal End 11 First Electrode (Pacing Electrode) 12 Second Electrode (Pacing Ring) 13 Third Electrode 14 Fixing Device 15 Processing Circuit 16 Motion Sensor 17 Pressure Sensor 18 Sound Sensor A Atrial Vector AA Atrial Activity AN Negative Mean Value AP Positive Mean Value As Atrial Event AV Atrial-Ventricular Delay AVN Atrioventricular Node B Reference D Threshold H HIS Bundle LA Left Atrium LBB Left Bundle Branch LV Left Ventricle M Intracardiac Tissue (Myocardium) N Noise Contribution P Pacing Vector PN Negative Peak Value PP Positive Peak Value PW Peak Width RA Right Atrium RBB Right Bundle Branch RV Right Ventricle S Signal Portion Scomb Combined signal portion Time t Delay times T1 to T3 TA Atrial interval TV Ventricular interval T blank Blanking window SAN Sinoatrial node V Ventricular vector VA Ventricular - atrial delay Vs Ventricular event W, W1 to W3 Investigation windows

Claims

Claim 1 A leadless pacemaker device (1) configured to provide cardiac pacing, comprising: a processing circuit (15) configured to generate a ventricular pacing signal for stimulating ventricular activity at a predetermined ventricular pacing rate; and a sensor array configured to receive sensing signals over a plurality of cardiac cycles in the leadless pacemaker device (1). The processing circuit (15) derives a combined signal portion (S ｃｏｍｂ ), and is configured to analyze the combined signal portion (S ｃｏｍｂ ) to obtain information regarding atrial events (As). The processing circuit (15) is configured to identify an atrial event (As) based on monitoring whether the combined signal portion (S ｃｏｍｂ ) exceeds a threshold value (D), a leadless pacemaker device (1). Claim 2 The processing circuit (15) is configured to sum a predefined number of signal portions (S) related to different cardiac cycles in order to obtain the combined signal portion (S ｃｏｍｂ ), the leadless pacemaker device (1) according to claim 1. Claim 3 The leadless pacemaker device (1) according to claim 1 or 2, wherein the processing circuit (15) is configured to obtain a signal portion (S) related to the cardiac cycle based on the sensing signal and based on a time window (W, W1 to W3) within the cardiac cycle. Claim 4 The leadless pacemaker device (1) according to claim 3, wherein the processing circuit (15) is configured to adaptively set the time window (W, W1 to W3) for the cardiac cycle based on a previous ventricular event (Vs). Claim 5 The leadless pacemaker device (1) according to claim 3 or 4, wherein the start of the time window (W, W1 to W3) is defined based on a predefined delay time (T1 to T3) following a previous ventricular event (Vs). Claim 6 The leadless pacemaker device (1) according to claim 5, wherein at least one of the predefined delay time (T1 to T3) and the length of the time window (W, W1 to W3) is set based on the actual heart rate. Claim 7 The leadless pacemaker device (1) according to any one of claims 1 to 6, wherein the sensor array has at least two electrodes (11 to 13) for receiving an electrical sensing signal indicative of atrial activity. Claim 8 The leadless pacemaker device (1) according to claim 7, having a housing (10) with a tip (100) and a distal end (101), the distal end (101) being located on a side of the housing (10) opposite the tip (100), one electrode (11, 12) being disposed in the vicinity of the tip (100) and another electrode (13) being disposed in the vicinity of the distal end (101), the electrical sensing signal being received using the electrode (11, 12) in the vicinity of the tip (100) and the electrode (13) in the vicinity of the distal end (101). Claim 9 The leadless pacemaker device (1) according to any one of claims 1 to 8, wherein the sensor array has at least one of a motion sensor (16), a pressure sensor (17), and a sound sensor (18).

10. A method of operating a leadless pacemaker device (1) configured to provide intracardiac pacing and having a sensor array and a processing circuit, wherein the sensor array receives sensed signals over a number of cardiac cycles, The processing circuit (15) derives a combined signal portion (S ｃｏｍｂ ) from a plurality of signal portions (S) of the sensed signal regarding the plurality of cardiac cycles, The processing circuit (15) analyzes the combined signal portion (S ｃｏｍｂ ) to obtain information regarding the atrial event (As) comprising, The processing circuit (15) identifies an atrial event (As) based on monitoring whether the combined signal portion (S ｃｏｍｂ ) exceeds a threshold value (D).

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