Implantable medical device configured to provide an intracardiac function

Abstract

The implantable medical device (1) configured to provide an intracardiac function comprises a body (10), a sensor device disposed on the body (10) and configured to receive a cardiac sense signal (S2), and a processing circuit (15) operatively connected to the sensor device. The processing circuit (15) processes the cardiac sense signal (S2) received using the sensor device to monitor the cardiac sense signal (S2) to detect whether an entry criterion is met, where the entry criterion is met if at least one signal sample (s(i-3)...s(i+3)) of the cardiac sense signal (S2) is less than an entry threshold (TH), and based on whether the entry criterion is met, to determine whether an atrial detection window (T) is in progress. センス ) to start the atrial detection window (T センス ) is configured to detect signal deflections in the cardiac sense signal (S2) potentially indicative of an atrial event (As).

Description

[Technical field]

[0001] The present invention relates generally to implantable medical devices for providing intracardiac functions, particularly pacing functions, such as ventricular pacing, and in particular VDD pacing. [Background technology]

[0002] In the form of an implantable medical device, e.g., a leadless pacemaker device or a cardiac stimulation device using a subcutaneously implanted pulse generator and one or more leads extending into the patient's heart, it may be desirable to provide stimulation to a ventricle of the patient's heart, e.g., the right ventricle, in synchrony with atrial activity. To this end, ventricular pacing, e.g., in a so-called VDD pacing mode, shall take into account an atrial sense signal in order to control ventricular pacing based on atrial events indicative of atrial activity.

[0003] In recent years, leadless pacemakers have been gaining attention. In contrast to subcutaneously implanted pacemakers using leads extending transvenously into the heart, leadless pacemakers avoid leads in that the pacemaker device itself is implanted in the heart and the pacemaker has a capsule shape for implantation in cardiac tissue, particularly in the right ventricle. Such leadless pacemakers exhibit the inherent advantage of not using leads, thereby reducing patient risks associated with transvenously accessing the heart, such as the risk of pneumothorax, lead dislodgment, cardiac perforation, venous thrombosis, etc.

[0004] A leadless pacemaker, or stimulator lead, may be specifically designed for implantation in the right ventricle, e.g., located near the apex of the right ventricle during implantation. For example, ventricular pacing may be indicated when dysfunction in the AV node occurs but sinus node function is intact and adequate. In such cases, so-called VDD pacing may be desirable, which specifically includes ventricular pacing with atrial tracking and thus requires a sense of atrial activity to pace the ventricles based on intrinsic atrial contractions.

[0005] VDD pacing is specifically motivated by the patient hemodynamic benefits of atrioventricular (AV) synchrony by taking advantage of adequate sinus node function to trigger ventricular pacing, potentially maximizing ventricular preload, limiting AV valve regurgitation, maintaining low mean atrial pressure, and allowing to modulate autonomic and neurohumoral reflexes.

[0006] Publications have discussed solutions using modalities to detect mechanical events of atrial contraction including sensing motion, sound, and pressure (see, for example, U.S. Patent Application Publication No. 2018 / 0021581, which discloses a leadless cardiac pacemaker including a pressure sensor and / or accelerometer for determining atrial contraction timing). Because mechanical events generally exhibit small signal amplitudes, signal detection based on mechanical events, such as motion, sound, or pressure, may be difficult to sense, especially when the implantable medical device is placed in the ventricle and thus quite far away from the atrium whose contraction is to be sensed. Furthermore, cardiac wall motion and blood movement generated by atrial contraction may not be directly translated to the ventricle, and cardiac hemodynamic signals such as motion, heart sounds, and pressure are likely to be affected by external factors such as posture and patient activity. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] US Patent Application Publication No. 2018 / 0021581 Summary of the Invention

[0008] In particular, it is an object to provide an implantable medical device and a method of operating an implantable medical device that enables ventricular pacing with atrioventricular synchrony and therefore requires reliable sensing of atrial events in order to provide ventricular pacing based on such atrial events.

[0009] Such needs are addressed by an implantable medical device configured to provide an intracardiac function having the features of claim 1.

[0010] In one aspect, an implantable medical device configured to provide an intracardiac function comprises a body, a sensor device on the body and configured to receive cardiac sense signals, and a processing circuit operatively connected to the sensor device, The processing circuit is configured to process the cardiac sense signals received using the sensor device to monitor the cardiac sense signals to detect whether an entry criterion is met, where the entry criterion is met when at least one signal sample of the cardiac sense signal is less than an entry threshold, and to initiate an atrial detection window for detecting a signal deflection in the cardiac sense signal potentially indicative of an atrial event within the atrial detection window based on whether the entry criterion is met.

[0011] The initiation criterion may also be, or may be replaced by, a sense detection criterion, in which case the atrial detection window allows monitoring of the signal for sense detection, so in this case this criterion appears to be a detection criterion and not an initiation criterion.

[0012] Generally, detection of an atrial event is assumed to occur within an atrial detection window, and to detect an atrial event, a signal deflection of a cardiac sense signal within the atrial detection window is monitored and processed to identify whether an atrial event may exist. Here, if an implantable medical device is implanted in a ventricle of a patient's heart, such as the right ventricle, signals related to atrial activity are generated in the far field, while ventricular signals related to ventricular activity are received in the near field. This makes the atrial signals generally smaller and noisier than the ventricular signals, which may make it difficult to distinguish the atrial signals from the ventricular signals.

[0013] In particular, signal portions related to atrial activity may be corrupted by signals derived from ventricular activity. For example, the end of a T wave associated with ventricular repolarization after a previous QRS complex in the intracardiac electrogram may extend into the atrial detection window, causing a portion of the T wave to be erroneously identified as an atrial event in the intracardiac electrogram signal. Furthermore, the atrial detection window may extend into the beginning of a subsequent ventricular complex, particularly the QRS complex in the intracardiac electrogram signal, making it difficult to easily determine the peak amplitude of an atrial event if the atrial event is identified near a subsequent ventricular event.

[0014] Therefore, in particular to be able to accurately identify atrial events without corruption by preceding waveforms not related to atrial activity (such as T waves of an intracardiac electrogram), it is proposed herein to dynamically set an atrial detection window based on signal monitoring. In particular, the atrial detection window shall be started only after an initiation criterion is met. The initiation criterion monitors whether at least one sample of the cardiac sense signal is smaller than an initiation threshold, and only if this is found, the atrial detection window is started.

[0015] Thus, the prior waveform, e.g., the T wave of an intracardiac electrogram signal, is monitored for sufficient decay to ensure that an atrial event can be detected within the atrial detection window without corruption of the signal portion associated with the prior non-atrial signal waveform. Because atrial events are detected based on signal deflection due to far-field activity, the signal deflection associated with atrial events is generally small in amplitude and may be noisy. By initiating the atrial detection window only when an initiation criterion is met, it can be ensured that the atrial detection window covers a portion of the cardiac sense signal that is likely associated only with atrial activity, thus improving the reliability of detection of atrial events and reducing the risk of atrial undersensing, which may lead to loss of atrioventricular (AV) synchrony.

[0016] In particular, by adaptively starting the atrial detection window based on a starting criterion that monitors the amplitude of the cardiac sense signal prior to the atrial detection window, the atrial detection window can be reached and false detection of an atrial event due to signal portions not associated with atrial activity can be avoided, thus improving the reliability of atrial capture.

[0017] The sensor device may in particular be formed by an electrode arrangement of one or more electrodes arranged on the body, so that by means of the sensor device an electrical signal can be received, such electrical signal representing an intracardiac electrogram (IEGM) recording and thus indicative of cardiac activity.

[0018] In another embodiment, the sensor device may be configured to sense cardiac sense signals in the form of pressure signals, acoustic signals, ultrasound signals, motion signals, and / or impedance signals.

[0019] In one embodiment, the body of the implantable medical device may be formed by a lead connectable to a generator of the implantable medical device, where the generator may be implanted in the patient, for example subcutaneously away from the heart, and the lead forming the body extends from the generator into the heart, such that the body with the sensor device disposed therein is positioned within the heart, for example within the right ventricle, and engages tissue of the right ventricle.

[0020] In another embodiment, the body may be formed by a housing of a leadless pacemaker device. In this case, the implantable medical device is formed as a leadless device that does not include leads extending into the heart from a location outside the heart to provide stimulation and / or sensing within the heart. The housing of the leadless pacemaker device may be placed on tissue with a distal end formed by the housing, and the sensor device may be placed (at least partially) on or near the distal end, for example, to engage the tissue when the leadless pacemaker device is placed on tissue with its distal end.

[0021] When the implantable medical device is a leadless pacemaker device, the housing provides encapsulation of the implantable medical device, which contains within the housing all components necessary for autonomous operation such as processing circuitry, power storage such as a battery, electrical and electronic circuitry, etc. The housing is liquid-tight so that the implantable medical device can be implanted in cardiac tissue and maintained within the cardiac tissue for extended periods of time to provide long-term continuous cardiac pacing operation.

[0022] In one embodiment, the initiation criterion is assumed to be met if a predetermined number of signal samples of the cardiac sense signal are less than the initiation threshold, and thus the processing circuitry is configured to monitor whether a predetermined number of the signal samples are below the initiation threshold, and only if this is the case is an atrial detection window initiated.

[0023] The signal samples herein may or may not be consecutive. In particular, it may be monitored whether a predetermined number of consecutive signal samples are below the initiation threshold. Only when such a number of consecutive samples is detected, the atrial detection window is started. Alternatively, if the signal samples do not need to be consecutive, the atrial detection window is started when a (total) number of signal samples according to the predetermined number of signal samples is found to be below the initiation threshold, regardless of whether the signal samples are consecutive or not.

[0024] The number of signal samples that need to fall below the initiation threshold to initiate an atrial detection window may be, for example, 1-20, for example 3-6, for example 4.

[0025] The number of signal samples that must fall below the initiation threshold to meet the initiation criterion may be programmable, allowing the user to define the number of samples by appropriately programming the implantable medical device.

[0026] In one embodiment, the processing circuit is configured to initiate an atrial detection window upon detection that the initiation criteria are met. Thus, the atrial detection window may be initiated as soon as the initiation criteria are found to be met. Thus, when it is detected that the pre-required number of signal samples falls below the initiation threshold, the atrial detection window is initiated and a signal deflection potentially indicative of an atrial event is monitored.

[0027] In another embodiment, the atrial detection window may not start immediately upon detecting that the entry criteria are met, but rather with a gap relative to when the entry criteria are met, which gap may be programmable.

[0028] In one embodiment, the processing circuitry is configured to blank a portion of the cardiac sense signal within a blanking window and to start monitoring the cardiac sense signal to detect whether an entry criterion is met after the end of the blanking window. The blanking window generally serves to suppress such signal portions that are likely not due to atrial activity. In particular, the blanking window should cover signal portions associated with QRS complexes and T waves in an intracardiac electrogram that are due to ventricular activity and thus generally exhibit large signal amplitudes. Since signals associated with atrial activity may be of much smaller amplitude relative to ventricular signal deflections, suppression of ventricular signal deflections can increase sensitivity to atrial signal deflections and distinguish waveforms associated with atrial activity from other signal portions.

[0029] The blanking window may generally be initiated in response to detection of a previous ventricular event. The blanking window generally must be long to ensure that the T wave of the intracardiac electrogram following the previous QRS complex is covered by the blanking window.

[0030] Once the blanking window has elapsed, an initiation criterion is initiated to monitor whether it has been met, whereby an initiation criterion is analyzed whether signal portions that are unlikely to be related to atrial activity have sufficiently decayed, and only if this is found (by comparing signal samples of the cardiac sense signal with an initiation threshold) an atrial detection window is initiated.

[0031] In one embodiment, the processing circuitry is configured to monitor the cardiac sense signal in a first processing state before the entry criteria are met. Prior to initiating the atrial detection window, the cardiac sense signal may be monitored in an unprocessed manner, particularly by not applying any particular signal processing. Thus, raw signal data of the cardiac sense signal is examined to evaluate the entry criteria.

[0032] In one embodiment, the processing circuitry is configured to monitor the cardiac sense signal in a second processing state within an atrial detection window to detect a signal deflection of the cardiac sense signal potentially indicative of an atrial event. Once the atrial detection window is initiated, an atrial event is searched for based on the cardiac sense signal in the second processing state based on checking of an entry criterion. In the second processing state, the cardiac sense signal may be processed, in particular by applying filtering, e.g., band-pass filtering, rectification, averaging, etc., to enable reliable detection of an atrial event based on the signal deflection within the atrial detection window. Thus, once the atrial detection window is initiated, signal processing of the cardiac sense signal may be turned on such that the cardiac sense signal within the atrial detection window is appropriately processed to enable reliable detection of an atrial event.

[0033] In one embodiment, the processing circuitry is configured to detect a signal deflection in the cardiac sense signal potentially indicative of an atrial event within the atrial detection window based on a comparison of the cardiac sense signal to a sense threshold within the atrial detection window. Thus, an atrial event is detected by comparing the cardiac sense signal to a sense threshold, and an atrial event is assumed to be present when, for example, a crossing of a sense threshold based on one or more signal values ​​is identified.

[0034] In one embodiment, the onset threshold is equal to the sense threshold, while in another embodiment the onset threshold may be different from the sense threshold.

[0035] In one embodiment, the processing circuitry is configured to determine a peak amplitude associated with an atrial event when a signal deflection potentially indicative of an atrial event is identified. In general, when an atrial event is detected, an associated peak amplitude will be determined, for example to enable setting of a sense threshold and possibly also a start threshold for a subsequent cardiac cycle. The sense threshold and possibly also the start threshold can be dynamically adjusted so that checking for atrial events can be improved by dynamically adjusting the sense threshold and possibly also the start threshold based on the peak amplitude.

[0036] In one embodiment, upon detection of an atrial event, a peak detection window may be initiated based on crossing of a sense threshold by the cardiac sense signal within an atrial detection window. Within the peak detection window, the cardiac sense signal is tracked to determine a maximum value of the cardiac sense signal within the peak detection window. The maximum value is then assumed to be the peak amplitude and used for further processing.

[0037] Using the peak amplitude, the processing circuitry may be configured to calculate a sense threshold for detecting an atrial event in a subsequent cardiac cycle. In particular, the processing circuitry may calculate a sense threshold for detecting an atrial event in a subsequent cardiac cycle using the following equation: ST = PC ATR(t) where ST is the current sense threshold, PC is the percentage ratio, and ATR(t) is the current average threshold reference at cycle t. The sense threshold may be updated using the average threshold criterion and a percentage ratio according to: The percentage ratio may be in the range of, for example, 0% to 100%, in particular 25% to 75%, and may be programmable.

[0038] In another embodiment, the average threshold criterion is determined by the following formula: ATR(t)=W·PA(t-1)+(1-W)·ATR(t-1) where W denotes an update weight that determines how much the average threshold criterion should change based on the previous peak amplitude, PA(t-1) is the peak amplitude determined for the previous cycle t-1, and ATR(t-1) is the previous average threshold criterion. Therefore, for a current cycle t, the average threshold criterion is determined based on the peak amplitude PA determined for that cycle t, and based on the previous valid average threshold criterion at cycle t-1. Thus, for each cycle in which an atrial event As is detected, the average threshold criterion is updated and newly calculated, such that the average threshold criterion is dynamically adjusted from cycle to cycle.

[0039] The average threshold criterion may be calculated, for example, as the average value of the peak amplitudes for a predetermined number of cardiac cycles in which an atrial event is detected, for example between 2 and 6 cardiac cycles, for example 4 cardiac cycles.

[0040] In one embodiment, the processing circuit includes a first processing channel having a first gain for processing a first processed signal derived from a sensor signal received via the sensor device, and a second processing channel having a second gain for processing a second processed signal derived from the sensor signal received via the sensor device, the second gain being higher than the first gain.

[0041] In general, an implantable medical device may be configured to process different processed signals. To obtain such processed signals, a sensor device is provided, which comprises, for example, one or more electrodes for receiving electrical signals from which the processed signals are derived. The processed signals herein may, for example, be obtained using a pair of electrodes, respectively, where the same pair of electrodes or different pairs of electrodes may be used to obtain the different processed signals. In the first case, a single electrical signal, such as an intracardiac electrogram, may be obtained from which different processed signals, i.e., the first processed signal and the second processed signal, are derived for separate processing. In the latter case, separate electrical signals, e.g., related to a ventricular sense signal and an atrial sense signal, may be received (i.e., by applying a sense optimized for the atrial sense), for example, to derive the first processed signal and the second processed signal from such different electrical signals, where the different electrical signals are received using different electrode pairs of the sensor device.

[0042] In one embodiment, the different processed signals are processed in different processing paths of the processing circuit, for which the processing circuit comprises a first processing channel for processing a first processed signal, the first processed signal relating to a near-field (particularly ventricular) sense signal which may be large such that the first processing channel exhibits a fairly low gain, for example depending on the placement of the implantable medical device in a ventricle of the patient's heart.

[0043] The processing circuit further comprises a second processing channel for processing a second processed signal, which may be associated with a far-field atrial sense signal that may have a small amplitude due to the distance between the implantation location and the source of the signal, for example, in the case of an implanted medical device placed in a ventricle. To enable reliable processing of the second processed signal, the second processing channel exhibits a higher gain than the gain of the first processing channel, such that features associated with atrial activity may be properly analyzed within the received signal.

[0044] When an implantable medical device is placed in, for example, a ventricle, it may be difficult to distinguish atrial events in a normal ventricular sense signal (e.g., obtained from a normal ventricular QRS sense channel) because atrial activity occurs in the far field and P waves resulting from atrial activity may exhibit small amplitudes relative to the QRS and T waves. Thus, the signal portion associated with far-field activity may be processed separately from signals associated with near-field activity in a second processing channel, where far-field events may be detected with greater reliability and improved timing accuracy.

[0045] The implantable medical device, in one aspect, is located completely or partially in the right or left ventricle.

[0046] In one aspect, the sensor arrangement is formed by an electrode arrangement comprising a first electrode disposed near a distal end of the body that is to be placed on the cardiac tissue with the implantable medical device implanted such that the first electrode is in contact with the cardiac tissue in a location effective for injecting a stimulation signal into the cardiac tissue, for example to induce a pacing action, in particular ventricular pacing.

[0047] In one embodiment, the electrode device includes a second electrode formed by an electrode ring extending circumferentially around the body. Alternatively, the second electrode may be formed, for example, by a patch or other conductive region formed on the body. The second electrode is located away from the tip of the body and is therefore located away from the tip-located first electrode.

[0048] In one embodiment, the processing circuit is configured to process a first signal sensed between the first electrode and the second electrode as the first processed signal. Such a first signal can be represented as a near-field vector received between a pair of electrodes, the first electrode and the second electrode. Since the first electrode and the second electrode can be located at a fairly close distance to each other in one embodiment, such an electrode pair is primarily suitable for receiving signals in the vicinity of the implantable medical device, i.e., in the near-field region within the ventricle when the implantable medical device is implanted in the ventricle. The sense signal received between the first electrode and the second electrode is provided to a first processing channel for processing, for example to detect near-field (e.g., ventricular) events in the signal.

[0049] In one embodiment, the body includes a remote location detached from the tip (e.g., at the distal end of a housing of a leadless pacemaker device), and the electrode device includes a third electrode disposed on the body at the remote location. The third electrode is operably connected to the processing circuitry to enable the processing circuitry to receive and process signals received via the third electrode.

[0050] In one embodiment, the processing circuit is configured to process a second signal sensed between the first electrode and the third electrode as the second processed signal. Such a second signal vector arising between the first electrode and the third electrode may be referred to as a far-field vector, with the first electrode and the third electrode exhibiting a greater distance relative to each other than the first electrode and the second electrode. The second signal may be processed to detect events in the far field, i.e., atrial contraction when the implantable medical device is placed in the ventricle, in particular, such that the second signal may capture intrinsic atrial activity prior to injection of a pacing stimulus.

[0051] A second signal sensed between the first and third electrodes may be used to sense intrinsic atrial contractions to provide atrial-ventricular synchrony by timely injecting a stimulus into a ventricular location of implantation of a pacemaker device after an atrial contraction. The second signal is provided to a second processing channel to process the signal to detect an atrial event therefrom to provide a pacing action based on the detected atrial event, thus enabling ventricular pacing under atrioventricular (AV) synchrony.

[0052] In one embodiment, the second processing channel includes a processing stage for distinguishing one wave portion from another wave portion in the second processed signal. The processing stage may be configured to apply at least one of band pass filtering, a blanking window to exclude a portion of the second sensor signal from further processing, moving average filtering, and rectification to the second processed signal, among others. The processing stage results in, among others, such waveform portions being separated and / or emphasized in the processed signal that may be indicative of, for example, an atrial event. When the implantable medical device is placed in a ventricle of the patient's heart, signal portions associated with atrial activity in the far field may have a much smaller amplitude than signal portions associated with ventricular activity in the near field. Thus, the processing serves to distinguish between different signal portions in order to identify such signal portions that may include signals associated with atrial activity in the far field.

[0053] For example, band-pass filtering can be applied to separate the P waves in an intracardiac electrogram, thus distinguishing the wave portions associated with the P waves from those associated with the QRS and T waves, which are due in particular to ventricular activity. Alternatively or additionally, other methods such as moving average filtering, differencing, or rectification of the signal may be applied. A moving average filter here can be used to smooth the processed signal. Rectification serves to easily compare the processed signal with a (single) threshold value to identify when the signal magnitude exceeds a predefined threshold.

[0054] In another aspect, a method of operating an implantable medical device to provide an intracardiac function includes receiving q cardiac sense signals using a sensor device disposed on a body of the implantable medical device; processing the cardiac sense signals received using the sensor device using processing circuitry operably connected to the sensor device to monitor the cardiac sense signals to detect whether an initiation criterion is met, where the initiation criterion is met when at least one signal sample of the cardiac sense signal is less than an initiation threshold, and initiating an atrial detection window for detecting a signal deflection in the cardiac sense signal potentially indicative of an atrial event within the atrial detection window based on whether the cardiac sense signal meets a detection criterion of exceeding a sense threshold for a programmed number of samples.

[0055] The advantages and advantageous embodiments mentioned above for the apparatus, as referenced above, apply equally to the method.

[0056] The various features and advantages of the present invention may be more readily understood by reference to the following detailed description and the embodiments illustrated in the drawings. [Brief description of the drawings]

[0057] [Figure 1] FIG. 1 is a schematic diagram of a human heart implanted with an implantable medical device in the form of a leadless pacemaker device. [Diagram 2] 1 is a schematic diagram of an implantable medical device. [Diagram 3] FIG. 1 is a schematic diagram of an implantable medical device showing signal vectors between different electrodes of the implantable medical device. [Figure 4] FIG. 2 is a schematic diagram of a processing circuit of one embodiment of an implantable medical device. [Figure 5A] FIG. 2 shows a first processed signal in the shape of an intracardiac electrogram (IEGM) processed by a first processing channel of the processing circuit. [Figure 5B] FIG. 4 shows a second processed signal processed by a second processing channel of the processing circuit. [Figure 6] FIG. 13 illustrates an example of a second processed signal within two cardiac cycles. [Figure 7] 1 is a schematic diagram of a human heart with an implantable medical device in the form of a cardiac stimulation device with a lead implanted in the right ventricle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0058] 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.

[0059] It should be noted that the embodiments do not limit the present invention but merely represent illustrative examples.

[0060] According to the present invention it is proposed to provide an implantable medical device which provides an intracardiac function, in particular ventricular pacing, specifically so-called VDD pacing.

[0061] Figure 1 shows in a schematic diagram the human heart, including the right atrium RA, the right ventricle RV, the left atrium LA and the left ventricle LV, in which the so-called sinoatrial node SAN is located in the wall of the right atrium RA, the sinoatrial node SAN is formed by a group of cells that have the ability to spontaneously generate electrical impulses that travel through the electrical conduction system of the heart, thus making the heart contract to pump blood through the heart. The atrioventricular node AVN is responsible for regulating the electrical conduction between the atria and the ventricles and is located in the inferior dorsal part of the interatrial septum near the opening of the coronary sinus. From the atrioventricular node AVN extends the so-called HIS bundle H, which is made up of cardiomyocytes specialized in electrical conduction and forms part of the 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.

[0062] In the case of an obstruction in the atrioventricular node AVN, the intrinsic electrical conduction system of the heart H may be disrupted, leading to potentially insufficient intrinsic stimulation of ventricular activity, i.e. insufficient or irregular contractions of the right and / or left ventricles RV, LV. In such cases, pacing of ventricular activity by a pacemaker device may be indicated, which stimulates ventricular activity by injecting stimulation energy into the intracardiac tissue, particularly the myocardium M.

[0063] In one embodiment, ventricular pacing is provided in an implantable medical device 1 in the form of a leadless pacemaker device having a body 10 formed by a housing of the leadless pacemaker device, as shown generally in FIG.

[0064] In another embodiment, as shown in FIG. 7 , the implantable medical device 1 may be a stimulation device having a generator 18 and at least one lead forming the body 10 of the implantable medical device 1 and extending intravenously from the generator 18 into the patient's heart.

[0065] Although typical implantable medical devices are designed to sense ventricular activity by receiving electrical signals from the ventricles RV, LV in which they are located, it may be desirable to provide a pacing operation that achieves atrioventricular (AV) synchrony by providing pacing to the ventricles in synchronization with intrinsic atrial activity. For such a pacing mode, also referred to as a VDD pacing mode, it is necessary to sense atrial activity and identify atrial events associated with atrial contractions in order to pace the ventricles based on such atrial events.

[0066] 2 and 3, in one embodiment, an implantable medical device 1 in the form of a leadless pacemaker device configured to provide intracardiac pacing, particularly in a VDD pacing mode, comprises a housing 10 enclosing electrical and electronic components for operating the implantable medical device 1. In particular, housed within the housing 10 is a processing circuit 15, which also comprises a communication interface for communicating with an external device, such as, for example, a programmer wand. Additionally, housed within the housing 10 are electrical and electronic components, such as a power storage unit in the form of a battery. The housing 10 provides encapsulation of the components housed therein, the housing 10 having, for example, the shape of a cylindrical shaft having a length of a few centimeters.

[0067] The implantable medical device 1 is to be implanted directly above the intracardiac tissue M. For this purpose, the implantable medical device 1 is provided in the region of the tip 100 with a fixation device 14, e.g. in the form of a Nitinol wire, which engages with the intracardiac tissue M in order to hold the implantable medical device 1 fixedly on the tissue in the implanted state.

[0068] The implantable medical device 1 in the embodiment of Figures 2 and 3 does not include leads, but receives signals related to cardiac activity by means of an electrode arrangement arranged on the housing 10, and also emits stimulation signals by means of such an electrode arrangement. In the embodiment of Figures 2 and 3, the implantable medical device 1 comprises different electrodes 11, 12, 13 constituting an electrode arrangement and serving to emit pacing signals towards the intracardiac tissue M to provide pacing, and to sense electrical signals indicative of cardiac activity, in particular indicative of atrial and ventricular contractions.

[0069] The first electrode 11 is referred to herein as a pacing electrode. The first electrode 11 is disposed at a tip 100 of the housing 10 and is configured to engage cardiac tissue M.

[0070] The second electrode 12 is referred to herein as a pacing ring. The second electrode 12 functions as a counter electrode to the first electrode 11, and a signal vector P generated between the first electrode 11 and the second electrode 12 provides a pacing vector P for emitting a pacing signal toward the intracardiac tissue M.

[0071] Additionally, the second electrode 12 functions as a sense electrode for sensing signals specifically related to ventricular contraction, and a signal vector V arises between the second electrode 12 and the first electrode 11, where the signal vector V is represented as a near field vector.

[0072] The second electrode 12 is placed away from the first electrode 11 and has, for example, a ring shape extending circumferentially around the housing 10. The second electrode 12 is placed, for example, at a distance of about 1 cm from the tip 100 of the housing 10 where the first electrode 11 is placed.

[0073] 2 and 3, the implantable medical device 1 further comprises a third electrode 13 located at the distal end 101 of the housing 10, which serves as a sense electrode for sensing signals indicative of cardiac activity in the far field. In particular, a signal vector A arises between the third electrode 13 and the first electrode 11, which picks up a signal indicative of, for example, an atrial contraction, represented as a far-field vector.

[0074] The electrodes 11, 12, 13 are in operative communication with a processing circuit 15 that is configured to cause the first electrode 11 and the second electrode 12 to emit pacing signals to provide stimulation to the ventricles. The processing circuit 15 is further configured to process signals received via the electrodes 11, 12, 13 to provide a sense of cardiac activity, in particular atrial and ventricular contractions.

[0075] If the implantable medical device 1 has the form of a stimulator comprising a generator 18 and leads extending from the generator 18, as shown in the embodiment of Figure 7, a similar electrode arrangement comprising, for example, three electrodes 11, 12, 13 may be implanted in the right ventricle RV and placed on leads extending to the right ventricle RV, as shown in Figure 7, and the above also applies to embodiments of the implantable medical device 1 having leads extending to the patient's heart. In this case, the processing circuit 15 may be part of the generator 18 and may be operatively connected to the electrode arrangement placed on the leads.

[0076] To provide pacing in the ventricle in which the implantable medical device 1 is located, particularly to enable pacing in VDD mode, a sense of atrial activity is necessary to provide a detected atrial sense marker for timing pacing in the ventricle to obtain atrioventricular (AV) synchrony. For this purpose, the implantable medical device 1 is implanted in endocardial tissue M in the right ventricle RV, whereby far-field signals, particularly from the right atrium RA (see FIGS. 1 and 9), are sensed to enable synchronous pacing in the right ventricle RV.

[0077] 4, the processing circuit 15 in one embodiment comprises two processing channels 16, 17 for processing different processed signals related to ventricular and atrial activity. Typically, in this specification, an intracardiac electrogram (IEGM) includes signal portions related to ventricular activity (particularly QRS waves) and atrial activity (particularly P waves), but the signal portions related to atrial activity originate from a source in the far field and are therefore much weaker and have a much smaller amplitude than the signal portions related to ventricular activity in the near field, i.e., occurring in close proximity to the implanted implantable medical device 1. For this reason, the two processing channels 16, 17 are associated with different gains G1, G2, the first processing channel 16 serving to process a first processed signal to identify ventricular events Vx with a significantly lower gain G1, and the second processing channel 17 configured to process a second processed signal to identify atrial events with a significantly higher gain G2.

[0078] In particular, the first processing channel 16 is connected to the electrode arrangement consisting of the electrodes 11, 12, 13, the first processing channel 16 being configured in particular to sense and process signals (near field vectors V in Figures 2 and 3) received via the electrodes 11, 12. The first processing channel 16 comprises a first amplification stage 161 having a gain G1, followed by a detection stage 162 configured to identify ventricular sense markers Vx from the first processed signals processed in the first processing channel 16.

[0079] The second processing channel 17 is similarly connected to the electrode arrangement consisting of the electrodes 11, 12, 13, and the second processing channel 17 may in particular be configured to process signals sensed via the far field vector A between the electrodes 11, 13 located at the tip 100 and the distal end 101 of the housing 10, as shown in Figures 2 and 3. The second processing channel 17 comprises a second amplification stage 171 having a second gain G2, followed by a processing stage 172 and a second detection stage 173.

[0080] The processing stage 172 serves to pre-process the amplified second processed signal. The detection stage 173 then serves to evaluate and analyze the second processed signal to identify atrial events within the second processed signal, and the second processing channel 17 then outputs an atrial sense marker As indicative of an atrial event detected within the processed signal.

[0081] Furthermore, the processing circuit 15 includes a timing stage 174 that uses timing information received from the first processing channel 16 and the second processing channel 17 to provide pacing timing, in particular VDD timing for achieving atrial-ventricular synchronous pacing.

[0082] To identify and analyze atrial events, the gain G2 of the second processing channel 17 is (significantly) higher than the gain G1 of the first processing channel 16. This generally makes it possible to analyze signal parts related to atrial events, but requires distinguishing such signal parts related to atrial events from other signal parts, in particular signal parts related to ventricular events Vx in the near field and thus much larger than signal parts originating from atrial events in the far field.

[0083] For example, band-pass filtering, windowing (e.g., partial blanking), smoothing by moving average filtering, and rectification may be performed within the processing stage 172. First or second order differencing can be applied to remove non-zero baselines while enhancing P-wave defects.

[0084] Figures 5A and 5B show examples of signals S1, S2 processed in different processing channels 16, 17, with Fig. 5A on the top showing signal S1 processed in a first processing channel 16 and Fig. 5B on the bottom showing signal S2 processed in a second processing channel 17. As a result of the processing, ventricular events Vx and atrial events As are identified and corresponding markers are output.

[0085] As is evident from FIG. 5B, the sensing of atrial events As is performed using a windowing scheme, in particular the blanking window T ブランク is employed to blank out signal portions of signal S2 potentially related to ventricular activity.

[0086] In particular, detection of a ventricular event Vx in the first processing channel 16 allows the (expected) timing between an atrial event As and a ventricular event Vx to be determined. According to such timing, the blanking window T ブランク The start and end points of can be set so that signal portions not associated with atrial activity can be excluded from processing. In this way, large ventricular signals can be suppressed so that signal portions associated with ventricular activity do not interfere with the detection of atrial events.

[0087] Blanking Window T ブランク During this time, the second processing channel 17 may be turned off. In particular, the amplifier stage 171 of the second processing channel 17 may be turned off to save power.

[0088] In general, the detection of an atrial event As is determined by the blanking window T ブランク As will be further described below with reference to FIG. センス is the blanking window T ブランク The atrial detection window T センス is the cardiac sense signal S2 and the signal portion that is likely not related to atrial activity within the blanking window T ブランク The initiation is adaptively based on an initiation criterion that considers whether the signal has sufficiently decayed after the end of

[0089] An atrial event As is detected within the atrial detection window T センス 5B, a threshold value ST is assumed to be present when the signal S2 crosses the sense threshold ST. The comparison may be based on a rectification of the sense signal S2. Alternatively, positive and negative sense thresholds ST may be used, which may be the same or different values. A threshold crossing here may be assumed when one signal value is greater than the sense threshold ST. Alternatively, a crossing of the sense threshold ST is assumed when a predetermined number of signal values, for example two or more consecutive or non-consecutive sample values, are greater than the sense threshold ST.

[0090] If an atrial event As is detected, as in the second cardiac cycle of FIG. 5B, the atrial event As is used for further processing, in particular to update the sense threshold ST and to achieve atrial-ventricular synchronous pacing.

[0091] In particular, an atrial event As is interpreted as the time point at which a crossing of the sense threshold ST is identified. At the time of the atrial event, a peak detection window PDW begins, and based on the data recorded during the peak detection window PDW, a peak amplitude PA is determined as the maximum signal value within the peak detection window PDW. This is shown in FIG. 5B.

[0092] Also, in case of detection of an atrial event As, an atrioventricular delay AVD may be determined and used for further processing. If no ventricular event Vx is detected after the atrioventricular delay AVD has elapsed, a pacing signal may be injected to cause ventricular stimulation.

[0093] As shown in Figure 5B, the peak amplitude PA is determined within a peak detection window PDW after detection of an atrial event As. In general, the peak amplitude PA here is determined by tracking the sense signal S2 and thus identifying the maximum value of the sense signal S2 within the peak detection window PDW.

[0094] The peak amplitude PA is determined during a peak detection window PDW after an atrial event As (and / or its detection). As shown in FIG. 5B (and further in FIG. 6), the peak detection window PDW is determined during the atrial detection window T センス Therefore, the peak amplitude PA may be between the atrial detection window T センス may be determined during the blanking window T ブランク Thus, in one embodiment, the peak amplitude PA may not be determined during an atrial detection window T after detection of an atrial event As. センス and within the peak detection window PDW.

[0095] In one embodiment, the peak amplitude PA may be used to update the sense threshold ST for the next cardiac cycle.

[0096] In particular, the processing circuitry 15 calculates the following equation: ST = PC ATR(t) where ST is the current sense threshold, PC is the percentage ratio, and ATR(t) is the average threshold reference for the current cycle t. The sense threshold ST may be updated using the average threshold criterion and the percentage ratio according to: The percentage ratio may be, for example, in the range of 0% to 100%, in particular 25% to 75%.

[0097] In another embodiment, the average threshold criterion is determined by the following formula: ATR(t)=W·PA(t-1)+(1-W)·ATR(t-1) where W denotes an update weight that determines how much the average threshold criterion should change based on the previous peak amplitude, PA(t-1) is the peak amplitude determined for the previous cycle t-1, and ATR(t-1) is the previous average threshold criterion. Therefore, for a current cycle t, the average threshold criterion is determined based on the peak amplitude PA determined for that cycle t, and based on the previous valid average threshold criterion at cycle t-1. Thus, for each cycle in which an atrial event As is detected, the average threshold criterion is updated and newly calculated, such that the average threshold criterion is dynamically adjusted from cycle to cycle.

[0098] The average threshold criterion may be determined, for example, based on an average number of previous cardiac cycles in which an atrial event was identified and a corresponding peak amplitude value was obtained, e.g., the average threshold criterion may be determined as an average of the peak amplitude values ​​in the previous cardiac cycles.

[0099] If no (valid) atrial event As is detected, the peak amplitude PA is not determined and the average threshold reference ATR is not updated. In this way, it is avoided that a false detection of an atrial event As may cause a false increase in the sense threshold ST and a subsequent loss of accurate atrial detection. This is the case in the first cardiac cycle as shown in Figures 5A and 5B, where no crossing of the sense threshold ST is detected and correspondingly no atrial event As is identified.

[0100] Referring now to FIG. 6, the atrial detection window T センス is generally intended to cover the portion of the cardiac sense signal S2 that is likely to be associated with atrial activity (as processed in second processing channel 17 of processing circuitry 15 as shown in FIG. 4). The signal portion not associated with atrial activity is within the atrial detection window T センス shall be excluded from

[0101] For this reason, in the embodiment of FIG. センス is the blanking window T ブランク The initiation criteria may be adaptively initiated based on evaluation of the initiation criteria following completion of the initiation criteria.

[0102] As can be seen from FIG. 6, which shows two subsequent cardiac cycles, the end of the preceding waveform, in particular the T wave of the intracardiac electrogram, is delayed by the blanking window T ブランク , and may reach the signal portion of the cardiac sense signal S2 associated with atrial activity. This is particularly true when the blanking window T ブランク This is evident from the first cardiac cycle, shown on the left side of Figure 6, where there is a tail of the preceding waveform after the end of the blanking window T. This is also seen in the second cardiac cycle, shown on the right side of Figure 6, where a peak likely related to the preceding T wave appears within the blanking window T. ブランク occurs after the end of

[0103] Therefore, the atrial detection window T センス is initiated only if the initiation criteria are met, checking whether a predetermined number of signal samples of the cardiac sense signal are below the initiation threshold TH.

[0104] For the initiation criterion to be met, it may be sufficient here for one signal sample to be below the initiation threshold TH, in another embodiment it may be required that more than one signal sample, for example 2, 3, 4 or more signal samples, are below the initiation threshold TH.

[0105] For the initiation criterion to be met, it may be checked whether a predetermined number of consecutive signal samples are smaller than the initiation threshold TH. If and only if this is the case, the initiation criterion is assumed to be true. In another embodiment, the signal samples do not have to be consecutive to meet the initiation criterion, but it is checked whether the total number of signal samples is smaller than the initiation threshold TH.

[0106] 6, it is assumed that the entry criterion is met when a predetermined number of consecutive signal samples (four signal samples in the illustrated example) are found to be less than the entry threshold TH. The number of signal samples herein may be programmable, and it may also be programmable whether or not the signal samples need to be consecutive to meet the entry criterion.

[0107] In the cardiac cycle on the left side of Figure 6, time T 開始 At , it is found that four consecutive signal samples s(i)...s(i3) are below the initiation threshold TH. Thus, the initiation criterion is met and the atrial detection window T センス will begin.

[0108] In the subsequent cardiac cycle, in FIG. 6 on the right, two signal samples s(i-3), s(i-2) are found to be below the start threshold TH. However, the subsequent signal sample s(i-1) is above the start threshold TH, and a new count of consecutive signal samples below the start threshold TH begins. 開始 Only at the time t1, four consecutive signal samples s(i)...s(i+3) are found to be smaller than the initiation threshold TH, at which point the atrial detection window T センス is initiated and detection of an atrial event begins using the detection scheme as described above with reference to Figures 5A and 5B.

[0109] Atrial detection window T センス is the time T when it is determined that the entry criteria have been met. 開始 However, at time T 開始 and atrial detection window T センスThere may be a gap between the start of

[0110] The initiation threshold TH is the threshold for the atrial detection window T センス The onset threshold TH may be equal to a sense threshold ST subsequently applied to detect an atrial event within the ventricular chamber, such that the onset threshold TH may be set to the sense threshold ST determined, for example, according to the scheme described above. In another embodiment, the onset threshold TH may differ from the sense threshold ST by, for example, a predetermined factor.

[0111] In another embodiment, the onset threshold TH is programmed to a fixed value and is not adapted on a cycle-by-cycle basis or related to the sense threshold ST. Additionally, the onset threshold TH does not have to be equal to the sense threshold ST.

[0112] The atrial sense markers As output by processing circuitry 15 can be used to achieve ventricular synchronous pacing. To this end, it can be detected whether a detected atrial sense marker As is followed by an intrinsic ventricular sense marker Vx occurring within a predetermined time delay window (corresponding to the atrioventricular delay AVD) after the atrial sense marker As, in which case no stimulation is required. If a ventricular sense marker Vx is not detected, a stimulation pulse can be emitted to cause synchronous pacing in the ventricles.

[0113] Conversely, asynchronous pacing can also be performed.

[0114] Utilizing the far-field electrical signals received by the implantable medical device can provide superior detection of far-field events, particularly atrial events, when the implantable medical device is implanted in the ventricle. Tracking of far-field events by using and evaluating the electrical signals can allow for increased consistency and reliability, particularly with respect to external factors such as posture and patient activity. [Explanation of symbols]

[0115] 1 Implantable medical devices 10 Main body (housing) 100 Tip 101 Far end 11 First electrode (pacing electrode) 12 Second electrode (pacing ring) 13 Third electrode 14 Fixed equipment 15 Processing circuit 16 Processing Channels 161 Amplification stage 162 Detection stage 17 Processing Channels 171 Amplification stage 172 Processing stage 173 Detection stage 174 Timing Stage 18. Generator A signal vector (atrial / far-field vector) As Atrial event (atrial sense marker) AVD atrioventricular delay AVN Atrioventricular Node G1, G2 gain H HIS Bundle LA Left atrium LAT Lower Absolute Threshold LBB Left bundle branch LV left ventricle M Intracardiac tissue (myocardial tissue) P signal vector (pacing vector) PA Peak Amplitude PDW Peak detection window RA right atrium RBB Right bundle branch RV right ventricle s(i-3)…s(i+3) signal samples S1, S2 signal SAN sinoatrial node ST Sense Threshold T ブランク Blanking Window T センス Detection Window T 開始 Start time TH Start threshold V signal vector (ventricular / near field vector) Vx Ventricular event (Ventricular sense marker)

Claims

1. An implantable medical device (1) configured to provide an intracardiac function, comprising: A main body (10); a sensor device disposed on the body (10) and configured to receive a cardiac sense signal (S2); a processing circuit (15) operatively connected to the sensor device for processing the cardiac sense signals (S2) received using the sensor device to: monitoring the cardiac sense signal (S2) to detect whether an entry criterion is met, the entry criterion being met when at least one signal sample (s(i-3)...s(i+3)) of the cardiac sense signal (S2) is less than an entry threshold (TH); and Based on whether the entry criteria are met, an atrial detection window (T センス ) to start the atrial detection window (T センス ) detecting a signal deflection of the cardiac sense signal (S2) potentially indicative of an atrial event (As). A processing circuit (15) configured as above. An implantable medical device (1).

2. The implantable medical device (1) of claim 1, wherein the body (10) is formed by a lead connectable to a generator (18) of the implantable medical device (1) or the body (10) is formed by a housing of a leadless pacemaker device.

3. 3. The implantable medical device (1) of claim 1 or 2, wherein the initiation criterion is met when a predetermined number of signal samples (s(i-3)...s(i+3)) of the cardiac sense signal (S2) are less than the initiation threshold (TH).

4. 2. The implantable medical device (1) of claim 1, wherein the initiation criterion is met when a predetermined number of consecutive signal samples (s(i-3)...s(i+3)) of the cardiac sense signal (S2) are less than the initiation threshold (TH).

5. 4. The implantable medical device (1) of claim 3, wherein the predetermined plurality of signal samples (s(i-3)...s(i+3)) is in the range of 1 to 20.

6. The processing circuit (15) detects that the initiation criteria is met and then determines whether the atrial detection window (T センス 2. The implantable medical device (1) of claim 1, configured to initiate a

7. The processing circuit (15) divides a portion of the cardiac sense signal (S2) into a blanking window (T ブランク ) and within said blanking window (T ブランク 2. The implantable medical device (1) of claim 1, configured to start monitoring the cardiac sense signal (S2) to detect whether the initiation criterion is met after completion of a cardiac insufficiency test (CIS) .

8. The implantable medical device (1) of claim 1, wherein the processing circuit (15) is configured to monitor the cardiac sense signal (S2) in a first processing state before the entry criterion is met.

9. The processing circuit (15) selects an atrial detection window (T) for detecting signal deflections in the cardiac sense signal (S2) potentially indicative of an atrial event (As). センス The implantable medical device (1) of claim 1, configured to monitor the cardiac sense signal (S2) during a second processing state within a first processing state.

10. The processing circuit (15) combines the cardiac sense signal (S2) and the atrial detection window (T センス 2. The implantable medical device (1) of claim 1, configured to detect a signal deflection of the cardiac sense signal (S2) potentially indicative of an atrial event (As) based on a comparison with a sense threshold (ST) in a cardiac stimuli (Cs ...

11. The implantable medical device (1) of claim 10, wherein the onset threshold (TH) is equal to the sense threshold (ST).

12. 2. The implantable medical device of claim 1, wherein the processing circuit is configured to determine a peak amplitude associated with an atrial event when a signal deflection potentially indicative of the atrial event is detected.

13. The implantable medical device (1) of claim 12, wherein the processing circuit (15) is configured to determine the peak amplitude (PA) associated with the atrial event (As) in a peak detection window (PDW) following the atrial event (As).

14. The implantable medical device (1) of claim 1, wherein the processing circuit (15) comprises a first processing channel (16) having a first gain (G1) for processing a first processed signal derived from a cardiac sense signal received via the sensor device, and a second processing channel (17) having a second gain (G2) for processing a second processed signal derived from the cardiac sense signal received via the sensor device, the second gain (G2) being higher than the first gain (G1).

15. A method for operating an implantable medical device (1) to provide an intracardiac function, comprising the steps of: receiving a cardiac sense signal (S2) using a sensor device disposed on a body (10) of the implantable medical device (1); processing the cardiac sense signals (S2) received using the sensor device using a processing circuit (15) operatively connected to the sensor device; monitoring the cardiac sense signal (S2) to detect whether an entry criterion is met, the entry criterion being met when at least one signal sample (s(i-3)...s(i+3)) of the cardiac sense signal (S2) is less than an entry threshold (TH); and Based on whether the entry criteria are met, an atrial detection window (T センス ) to start the atrial detection window (T センス ) detecting a signal deflection of the cardiac sense signal (S2) potentially indicative of an atrial event (As). Steps and A method comprising:

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