Intracardiac medical device and method of operation thereof

Abstract

The present invention is directed to an intracardiac medical device (10) having a processing unit (120) and a detector (126a) configured to detect time-dependent electrical signals of a heart (20), such as an intracardiac electrogram, including a ventricular event, and to transmit the detected electrical signals to the processing unit (120), the processing unit (120) configured to classify a current intrinsic ventricular event (Vi, 205) of the received electrical signals as a normal sensed event (Vs) or a premature ventricular contraction (VES, 209). The present invention is further directed to a method of operating such a medical device (10), a computer program product, and a computer readable data carrier.

Description

[Technical field]

[0001] The present invention relates generally to intracardiac medical devices, methods of operating such medical devices, corresponding computer program products and computer readable data carriers.

[0002] Intracardiac medical devices, such as Implantable Leadless Pacers (ILPs), (conventional) leaded pacemakers or Implantable Cardiac Defibrillators (ICDs), are generally known.

[0003] An implantable intracardiac leadless pacemaker (also known as an implantable leadless pacemaker - ILP) is a miniature pacemaker that is implanted entirely within the patient's ventricle (V) or atrium (A). ILP is considered the future of cardiac pacing. Due to significant device size constraints, ILPs have small battery capacities.

[0004] A pacemaker is generally a medical device that generates electrical pulses delivered by electrodes connected to or fixed to the pacemaker to cause the chambers of the heart muscle (i.e., atria and / or ventricles) to contract and thus pump blood. In doing so, the device replaces, enhances, and / or regulates the function of the heart's electrical conduction system. One purpose of a pacemaker is to maintain an adequate heart rate, either because the heart's natural pacemaker is not fast enough or because there is a block in the heart's electrical conduction system. Today's pacemakers are externally programmable, allowing health care professionals (HCPs) to select the optimal pacing mode for each individual patient. The pacing function of the ILP (and traditional pacemakers) may have the goal of remaining synchronized with the heart's natural activity as much as possible.

[0005] Furthermore, pacemakers are known to use a specific rate to determine when to pace the heart. This specific rate can be achieved by counting clock signals for intervals corresponding to this specific rate. The simplest pacemakers use a fixed, typically programmable, rate that meets the patient's needs under most circumstances. It is common to use a sensor-derived rate based on demand-correlated measurements, such as acceleration. To replace a dysfunctional AV conduction signal, an AV-synchronous pacemaker attempts to pace the ventricles at a rate that corresponds to a detected atrial event (e.g., atrial contraction or depolarization events). It is also possible to estimate physiologically missing electrical heart rate signals derived from separate sensors from other systems in the body (e.g., the brain and baroreceptors). The intrinsic rate used by all pacemakers today is the intrinsic rate of the heart.

[0006] The primary goal of the ILP is to provide support similar to that provided in bradycardia management in conventional pocket-based leaded pacemakers, but via a device that is sized at up to 10% of the conventional overall volume. A VDD mode of operation can be achieved using such an ILP based on the detected electrical signals of a detector that determines the cardiac time-dependent electrical signals, including ventricular events, such as ventricular contraction or depolarization events. While the small size allows the leadless implant to be placed within the blood volume of the patient's heart, and the elimination of leaded connections to the myocardium reduces the risk of regurgitation and infection, this approach eliminates the ability to directly measure cardiac signaling originating from multiple heart chambers, and instead uses an implant that resides entirely within a single heart chamber, e.g., a ventricle. Thus, to facilitate synchronized output from the device, leadless embodiments need to collect heart chamber information that is readily available to the leaded system "at a distance." This capability requires that the affiliate mode support architecture provide a means to effectively manage behaviors that are subject to unreliability, e.g., in the quality of input signaling and event detection, such as the atria.

[0007] An intracardiac medical device, such as a (conventional) leaded pacemaker or an ICD, can sense the activity of a patient's heart in a manner similar to the ILP described above. An ICD provides a defibrillation function to treat life-threatening arrhythmias, while an intracardiac cardiac rhythm monitor collects data about the patient's heart. Like the ILP described above, such a device may be contained within the ventricle (V) or atrium (A) of the patient's heart, at least for a predetermined period of time, and therefore may face the same challenges as the ILP described above.

[0008] A ventricular extrasystole (VES), also known as a premature ventricular contraction (PVC), is a premature contraction of the ventricles that is not conducted from the atria but rather originates in the ventricle itself. When a patient with normal AV conduction experiences a single VES, the VES is usually preceded by a short interval from the previous ventricular event and is followed by a long compensatory pause interval before the next ventricular event.

[0009] A conventional dual-chamber pacemaker with an atrial lead can classify a VES event based on the presence or absence of an atrial event preceding an intrinsic ventricular event. However, especially for intracardiac medical devices that do not have a detector directly in the atrium, atrial sensing must be based on an atrial signal from the ventricle, e.g., seen by a device in the ventricle. Thus, atrial sensing may be less reliable and more prone to undersensing than for conventional dual-chamber pacemakers. Thus, identification of VES events using classical techniques for intracardiac medical devices may not be as robust as for conventional dual-chamber pacemakers.

[0010] Although individual VES events are generally not clinically significant, a larger number of VES events may be clinically significant, making it beneficial for implantable cardiac devices to provide statistics on the prevalence of VES events. Additionally, because intrinsic heart rate timing is generally altered following VES, an intracardiac leadless pacemaker may be able to better maintain synchronization with the intrinsic activity of the patient's heart by altering its pace timing following VES. To enable this, VES classification of ventricular events needs to be performed in real time.

[0011] Therefore, there is a need for an intracardiac medical device and corresponding method of operation that allows for reliable identification of VES events in real time.

[0012] The above mentioned problem is solved by a method for operating an intracardiac medical device with the features of claim 1, by a corresponding intracardiac medical device with the features of claim 8, by a computer program product with the features of claim 14 and by a computer readable data carrier with the features of claim 15. The computer program product may be software routines and / or hardware support means associated with the intracardiac medical device.

[0013] The above problem is particularly solved by a method of operating an intracardiac medical device in a patient's heart, the medical device having a processing unit and a detector, the detector detects a cardiac time-dependent electrical signal, such as an intracardiac electrogram (IEGM), including a ventricular event, transmits the detected electrical signal to the processing unit, and the processing unit classifies the current intrinsic ventricular event of the received electrical signal as a ventricular extrasystole (VES) if the time distance (or time interval or elapsed time) between the current intrinsic ventricular event and the immediately preceding ventricular event satisfies at least one pre-defined prematureness criterion, otherwise classifies the current intrinsic ventricular event as a non-VES ventricular event. For example, the RR peak time distance between the detected R peak of the current intrinsic ventricular event and the detected R peak of the immediately preceding ventricular event is evaluated with respect to at least one pre-defined prematureness criterion. In the above example, the R peak of the current intrinsic ventricular event and the R peak of the immediately preceding ventricular event are utilized to determine the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event. Other signal features of the electrical signal (e.g., IEGM), such as the Q or S components of the ventricular depolarization, can also be used to determine the temporal distance.

[0014] The term "most recent ventricular event" means that the ventricular event is taken from the most recent cardiac cycle of the patient's heart.

[0015] The intracardiac medical device may be, for example, an ILP, an ICD or a single lead pacemaker.

[0016] In the context of the present invention, the processing unit is generally considered as a functional unit of the pacemaker that interprets and executes instructions, having an instruction control unit and an arithmetic and logic unit. The processing unit may comprise or be a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a discrete logic circuit, or any combination thereof. The processing unit may alternatively or additionally be realized using dedicated integrated hardware logic circuits, especially in the case of an ILP, due to its small size and extremely limited power. The processing unit may comprise a state determination module, which, in relation to the ILP as a medical device, is configured to dynamically select one of a plurality of states and use the selected state to determine ventricular pacing time and / or rate information to meet the actual therapeutic needs of the patient. Examples of different states for an ILP are described in more detail below.

[0017] The processing unit processes the electrical signal data of the patient's heart received from the detector. The detector is particularly configured to detect time-dependent electrical polarization and repolarization field signals, such as intracardiac electrograms (IEGMs). These signals include signals caused by depolarization and repolarization of the atria (hereinafter intrinsic atrial events) and electrical signals caused by depolarization and repolarization of the ventricles (hereinafter intrinsic ventricular events). The intrinsic atrial events may be far-field signals (e.g. electrical signals) if the medical device, e.g. the ILP, is located in one of the ventricles. The detector can pre-process these data, for example digitizing the signals, filtering them, and / or amplifying them.

[0018] The electrical signal of the detector is transmitted to a processing unit which senses intrinsic ventricular events and, where applicable, intrinsic atrial events from the electrical signal, e.g., from the P-waves and from the QRS complexes, particularly the R-peaks of the QRS complexes. Since the electrically measured P-waves in the far field are of very small amplitude compared to the near field ventricular signals, a large amplification can be used during the signal where the P-waves are expected, compared to the time intervals of the QRS and T-waves. Alternatively, the electrical signal input provided by the sensor may be split into two channels inside the processing unit, one for the atrium and one for the ventricle. Each channel has its own amplification and filtering scheme for detecting intrinsic atrial and intrinsic ventricular events, respectively.

[0019] The processing unit may further include a counter and a clock. The counter can be used to count the clock signals of the clock. The counter can be initiated at a sensed atrial or ventricular depolarization, respectively, and count the number of clock periods until the next atrial or ventricular depolarization occurs, or a ventricular pacing is provided by the pacing signal generator, thereby determining the time distance between the current intrinsic ventricular event and the immediately preceding ventricular event, e.g., the time distance of the RR peak.

[0020] The pacemaker may have a data memory, which may include any volatile, non-volatile, magnetic, or electrical medium, such as a random access memory (RAM), a read-only memory (ROM), a non-volatile RAM (NVRAM), an electrically erasable programmable ROM (EEPROM), a flash memory, or any other memory device. The data memory stores the above and below mentioned thresholds and conditions, which are required by the processing unit during the processing of the steps described above and below. The data memory may further store measured values ​​of the time distances, such as RR peak time distances, for the current intrinsic ventricular event and the immediately preceding ventricular event, if applicable, the actual duration of one cardiac cycle or the corresponding actual heart rate, and if applicable, the expected duration of one cardiac cycle.

[0021] According to the above-described method of operation of the medical device, the processing unit classifies a current intrinsic ventricular event of the received electrical signal as a ventricular extrasystole (VES) if the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event meets at least one predefined prematureness criterion. If none of the at least one prematureness criterion is met, the current intrinsic ventricular event is classified as a "normal" ventricular event, hereinafter referred to as a "non-VES event" (Vs). Prior to the VES classification, the processing unit can determine whether the current ventricular event is an intrinsic ventricular event or a ventricular paced event, for example, by the timing of the event and / or the signal shape.

[0022] The current intrinsic ventricular event is the most recently detected intrinsic ventricular event, and the previous ventricular event may be an intrinsic ventricular event or a ventricular paced event detected by a detector or delivered by a device within the previous cardiac cycle.

[0023] In one embodiment, the prematureness criterion is met when the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event is significantly less than the actual or expected duration of one cardiac cycle and / or is less than or equal to a predetermined cardiac cycle prematureness duration threshold.

[0024] For example, the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event is equal to or less than a prematureness threshold determined from the expected duration of one cardiac cycle in several possible ways: - The premature threshold is determined as the product of a fixed or programmable multiplication factor (e.g., 0.5-0.95) and the expected duration of one cardiac cycle, or - The premature threshold is determined as a fixed or programmable duration (50-500 ms) shorter than the expected duration of one cardiac cycle.

[0025] In this regard, in one embodiment, the expected duration of a cardiac cycle is the duration of the most recent cardiac cycle without any VES events or is the average of the durations of a predefined number of most recent cardiac cycles without any VES events, for example, the average of the most recent non-VES cardiac cycle durations may be maintained as an average of a rolling interval buffer of 1 to 64 cycles, or as an exponential moving average with weighting ranging from 1 (no history, just the most recent interval) to 1 / 64 (longer history with each cycle contributing 1 / 64 to the average). In at least one embodiment, the upper and lower expected durations are the actual durations.

[0026] In one embodiment, the cardiac cycle premature duration threshold may be a fixed or programmable duration threshold (eg, a single value from 300 ms to 1000 ms).

[0027] The above classification of ventricular events as VES or non-VES events allows the VES event to be classified immediately (in real time) without waiting for measurement of the interval after a possible VES event, allowing the pacemaker to modify its behavior for subsequent cycles, e.g., to accommodate for the expected compensatory pause in intrinsic activity immediately following a VES, thereby improving the ability to maintain far-field atrial sensing and AV synchrony after a VES.

[0028] In one embodiment, if an atrial event is detected by the processing unit from the received electrical signal after the time of the R-peak of the previous ventricular event and / or at a time distance from the current intrinsic ventricular event that is shorter than the duration of the actual cardiac cycle and / or shorter than a predetermined normal cardiac cycle length, the predetermined prematureness criterion is stopped from being applied to the time distance between the current intrinsic ventricular event and the previous ventricular event, and the current intrinsic ventricular event is classified as a non-VES ventricular event. This means that the intrinsic atrial event preceding the intrinsic ventricular event in question (the current intrinsic ventricular event) is used to exclude it from classification as a VES. In other words, the intrinsic atrial event sensed as valid between the preceding ventricular event and the intrinsic ventricular event in question prevents the ventricular event from being classified as a VES. Thus, in this embodiment, the VES must be preceded by a non-VES cardiac cycle that does not meet at least one prematureness criterion and must not be preceded by a valid sensed atrial event. Thus, classification of the VES by the medical device is based on a combination of at least one prematureness criterion and, if applicable, atrial sensing information. Thus, VES classification is based on the prematureness of the ventricular event, and the presence of atrial information, if applicable, may enable an intracardiac leadless pacemaker implanted in the ventricle to more accurately classify VES events, even during periods of intermittent atrial sensing.

[0029] In one embodiment, the application of the predefined prematureness criteria to the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event is at least temporarily suspended or disabled, and the processing unit classifies the current intrinsic ventricular event as a non-VES ventricular event at least during the period when at least one of the multiple states is used by the state determination module of the processing unit, and such state can be adapted by the processing unit of the ILP to determine, for example, ventricular pacing time and / or rate information to meet the actual therapeutic needs of the patient. This allows VES classification to be performed only when relevant (e.g., by attempting atrial sensing, so that atrial information is available and the ILP activity is more likely to be synchronized with the intrinsic cardiac activity). This means that VES classification can be enabled and disabled separately in separately programmed modes (e.g., VDD mode) or in separate states within a mode (e.g., atrial tracking state in VDD mode or motion sensor drive state in VDD mode).

[0030] One exemplary state that may be controlled by the above-mentioned state determination module of the processing unit of the ILP to determine ventricular pacing time and / or rate information is VDD mode with atrial tracking. This mode assumes that the patient has some form of intrinsic AV conduction disorder, either completely or intermittently. It is also assumed that the sinus node is generally sufficient, and the VDD mode tracks the sinus rhythm and provides AV synchronization. The AV delay can be determined based on the actual heart rate (corresponding to the actual duration of one cardiac cycle) and can be set to the normal time difference between the intrinsic atrial contraction or depolarization and the intrinsic ventricular contraction or depolarization. The current AV delay can be determined from the actual heart rate by known calculations or by using a look-up table contained in the data memory. The current AV delay changes with the actual heart rate. Alternatively, a predetermined fixed AV delay may be used.

[0031] "Ventricular pacing time and / or rate information" includes any timing information required for a pacing signal generator of the ILP, connected to a processing unit, to generate a ventricular pacing signal at the correct time, i.e., according to a treatment plan. The ventricular pacing time and / or rate information may be determined or defined in part by an AV delay and / or a heart rate and / or a cardiac cycle duration. In one embodiment, the ventricular pacing time and / or rate information may have a hysteresis time that is added to the AV delay, whereby pacing is delayed slightly to allow more time for sensing an intrinsic ventricular event.

[0032] Based on the pacing control signal, an electrical pacing signal is generated by the pacing signal generator of the ILP and transferred to the electrode, which applies the signal to the cardiac tissue adjacent to the electrode. The pacing signal is a pulse starting at a desired time and having a desired intensity and duration. Furthermore, the pulse shape may be varied. The pacing control signaling is used by the processing unit to instruct the pacing signal generator on details associated with the duration, timing and amplitude of the prescribed therapeutic output pulse. In particular, the ventricular pacing control signal includes ventricular pacing time and / or rate information. In one embodiment, when operating according to the VDD mode, if an intrinsic ventricular event (e.g., AV delay) is detected within a predetermined period of time following a detected intrinsic atrial event, the pacing signal is not determined (i.e., inhibited) or not transferred to the electrode.

[0033] In a different state, a so-called intermediate state, the ventricular pacing time and / or rate information may be determined from increasing the initial heart rate to a predefined pacing rate, e.g., the patient's resting rate. The initial heart rate may be the actual heart rate at the time the state determination module switches to the intermediate state. The intermediate state may be transitioned to another state as soon as the predefined pacing rate is reached. The goal of such state transitions is to ensure the prescription of baseline bradycardia mitigation therapy, to minimize the occurrence of noticeable symptoms by avoiding abrupt rate changes, and to return the device / patient interaction to optimal conditions with minimal delay, while also striving to adapt to measurable patient needs. In another intermediate state, the processing unit may attempt AV resynchronization using tracking of intrinsic atrial and ventricular events, thereby synchronizing the pacing with the intrinsic activity of the heart, e.g., returning to a state using VDD mode with atrial tracking.

[0034] In one embodiment, the state determination module is configured to select a state in which the ILP uses signals received from at least one second detector capable of detecting a patient's time-dependent activity, such as an accelerometer, a vibration sensor, an impedance sensor, an acoustic sensor (including ultrasound) and / or another mechanical, electrical and / or magnetic sensor, to determine ventricular pacing time and / or rate information, depending on whether the use of the respective second detector is permitted, for example, by the HCP. This state may be a VVI-R mode. This state has the advantage that the HCP can better adapt the operation of the cardiac pacemaker to the patient's needs when the patient is active. Thus, in this state, the patient's activity is tracked, and the ILP and its processing unit may be configured to turn off any functionality for monitoring atrial input signaling. This increases the life of the power source (battery). A state of operating according to a known VVI mode using a pacing rate predefined for this mode may be provided by the processing unit and monitored by the state determination module.

[0035] For example, VES classification can be separately enabled during states having AV sync tracking conditions, e.g., in states using VDD mode, and can be disabled in intermediate states where AV resynchronization is attempted, and / or in states where patient activity is tracked using the second sensor described above (and operating without AV sync), and / or in states using VVI mode. In this embodiment, VES classification is only performed for states where the feature is enabled.

[0036] The ability to enable and disable VES classification in different conditions allows VES classification to be performed only when relevant (e.g., only when atrial information is available and, in the case of ILP, only attempting atrial sensing so that pacemaker activity is more likely to be synchronized with intrinsic cardiac activity).

[0037] Because intervals that include VES cycles are not indicative of a true intrinsic heart rate, these intervals are excluded from use by the medical device to update the VES prematureness criteria described above. This prematureness-based VES classification may therefore be susceptible to a "VES lock-in" behavior, where a pattern of repeated VES classification caused by a long prematureness threshold can prevent the prematureness threshold from being updated, thereby perpetuating a pattern of VES classification that is unlikely to indicate a true ventricular extrasystole. For example, if the conducted intrinsic rate suddenly rises without any atrial sensing information, a rapid conducted ventricular event may be consistently misclassified as a VES event based on the long prematureness threshold. In this condition, the VES classification continually prevents the prematureness threshold from being updated to a shorter value consistent with the new intrinsic rate, which may allow this condition to persist indefinitely.

[0038] Thus, in one embodiment, application of the predefined prematureness criterion to the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event is at least temporarily suspended or disabled, and the processing unit classifies the current intrinsic ventricular event as a non-VES ventricular event, for example using a VES counter (VES up / down counter), at least during the period when the predefined VES termination criterion is met, where each classified VES event increments the VES counter and each non-VES ventricular event (including ventricular pacing events) decrements the VES counter. For example, at least one of the following VES termination criteria can be applied: - if the VES counter value is greater than or equal to a predefined stop threshold (e.g., the first counter maximum value and the stop threshold are programmable, e.g., from 1 to 32), the VES stop criterion is met; or - VES termination criteria is met if the VES counter value is equal to or greater than X of Y ventricular events from the most recent cycle classified as VES events (e.g., X and Y are 1 to 32); or A VES stop criterion is met when a predefined number N of consecutive VES events occur (eg, N is 1 to 32).

[0039] In one embodiment, if a predetermined VES re-enabling criterion is met, the application of a predetermined prematureness criterion to the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event is re-enabled. For example, If the VES counter value is less than a predetermined re-enabling threshold (e.g., the second counter maximum value and the re-enabling threshold are programmable, e.g., from 1 to 32), a VES re-enabling decision is met; or - VES reactivation criteria are met if fewer than X ventricular events out of Y most recent cardiac cycles are classified as VES events (e.g., X and Y are between 1 and 32); or - if a predefined VES deactivation timeout (e.g., 1 to 60 seconds) has elapsed, the VES reactivation criteria is met, or - VES re-activation criteria are met when a predefined number of cardiac cycles with VES pauses (eg, 1-32 ventricular events) have occurred.

[0040] The ability to temporarily suspend and re-enable VES classification allows for the recognition of "VES lock-in" situations where VES events are frequently classified as ILP. These situations may benefit from pausing VES classification, allowing the measured ventricular interval to be used to update an internal ILP value related to pace timing and / or prematureness thresholds used for future VES classification.

[0041] In one embodiment, the above-mentioned method is implemented as a computer program (executed in or within the intracardiac medical device, in particular using a processing unit thereof), which is a combination of (computer) instructions and data definitions as specified above and below that enable computer hardware to perform computational or control functions and / or operations, or is a syntactic unit consisting of declarations, statements or instructions conforming to the rules of a particular programming language and necessary for the functions, tasks or problem-solving means specified above and below.

[0042] Further disclosed is a computer program product comprising instructions which, when executed by a processing unit of an intracardiac medical device, cause said processing unit to perform the steps of the method described above. Accordingly, a computer readable data carrier storing such a computer program product is described.

[0043] The above-mentioned problem is further solved by an intracardiac medical device having a processing unit and a detector configured to detect a cardiac time-dependent electrical signal, such as an intracardiac electrogram, including a ventricular event and transmit the detected electrical signal to the processing unit, wherein the processing unit is configured to classify a current intrinsic ventricular event of the received electrical signal as a ventricular extrasystole (VES) if the temporal distance between the current intrinsic ventricular event and an immediately preceding ventricular event satisfies at least one predetermined prematureness criterion, and to classify the current intrinsic ventricular event as a non-VES ventricular event otherwise.

[0044] The described embodiments of the method for operating a medical device also apply to the above-mentioned medical devices and provide similar advantages - in this respect reference is made to the above-mentioned embodiments of the method.

[0045] In one embodiment of the medical device, the processing unit is configured to satisfy the prematureness criterion when the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event is significantly shorter than the expected duration of one cardiac cycle and / or is less than or equal to a predetermined cardiac cycle prematureness duration threshold, for example, the expected duration of one cardiac cycle being the duration of a most recent cardiac cycle without any VES or the average of the durations of a predetermined number of most recent cardiac cycles without any VES.

[0046] In one embodiment of the medical device, the processing unit is configured to stop applying the predetermined prematureness criteria to the temporal distance between the current intrinsic ventricular ventricular ventricular event and the immediately preceding ventricular event and classify the current intrinsic ventricular event as a non-VES ventricular event if an atrial event is detected by the processing unit from the electrical signal received after the time of the R peak of the immediately preceding ventricular event and / or if the atrial event is detected at a temporal distance from the current intrinsic ventricular event that is shorter than the duration of the actual cardiac cycle and / or shorter than a predetermined cardiac cycle prematureness duration threshold.

[0047] In one embodiment of the medical device, the processing unit is configured such that application of a predetermined prematureness criterion to the temporal distance between a current intrinsic ventricular event and a immediately preceding ventricular event is at least temporarily suspended or disabled, and the current intrinsic ventricular event is classified by the processing unit as a non-VES ventricular event at least during the period in which at least one predetermined state of the plurality of states is used by the state determination module of the processing unit.

[0048] In one embodiment of the medical device, the processing unit is configured such that application of a predetermined prematureness criterion to the temporal distance between a current intrinsic ventricular event and a immediately preceding ventricular event is at least temporarily suspended or disabled, e.g., by using a VES counter, such that the current intrinsic ventricular event is classified by the processing unit as a non-VES ventricular event at least during the period during which the predetermined VES suspension criterion is met.

[0049] In one embodiment of the medical device, the processing unit is configured to re-enable application of a predetermined prematureness criterion to a temporal distance between a current intrinsic ventricular event and a immediately preceding ventricular event if a predetermined VES re-enablement criterion is met.

[0050] The above-mentioned method and the medical device together allow reporting of VES prevalence statistics to HCP. For this purpose, the medical device can have further modules, such as a communication unit for communicating with a remote computer. The communication unit can exchange messages with an external (at least partially outside the body) remote computer, for example, unidirectionally or bidirectionally. The communication can be provided wirelessly through the patient's body, preferably acoustically, conductively and / or magnetically coupled, and / or through air, using electromagnetic waves in the radio frequency range, such as MICS band, Bluetooth, WLAN, ZigBee, NFC, Wibree or WiMAX, or through IrDA or free-space optical communication (FSO) in the infrared or optical frequency range, or wired (electrical and / or optical communication). The remote computer is a functional unit that can perform substantial calculations, including many arithmetic and logical operations, without human intervention, such as a personal mobile device (PMD), desktop computer, server computer, cluster / warehouse scale computer or embedded system. The units and components of the medical device may be contained within a hermetically sealed housing.

[0051] In one embodiment, the intracardiac medical device may have a power source, such as a battery, for providing power to the modules / units / components of the medical device, and thus the power source is electrically connected to each module / unit / component of the medical device.

[0052] In one embodiment, when the medical device is an ILP, the medical device may have electrodes for applying an electrical pacing signal provided by a pacing signal generator. The electrodes are electrically connected to the pacing signal generator via a header of the ILP. One electrode may be located at the distal end of the ILP, near a fixation member with which the ILP is fixed to the tissue of the patient's heart, for example against or in the tissue of the ventricle. A second electrode may be located at the proximal end of the ILP or in a part of the ILP housing that may be used, for example, as a counter electrode. In one embodiment, the electrodes may additionally be adapted to detect intrinsic ventricular or intrinsic atrial events, in each case by picking up the electrical potential over time. For this purpose, the electrodes may be part of the detector of the medical device.

[0053] These features also allow an intracardiac leadless pacemaker to adjust pace timing following VES to maintain AV synchrony.

[0054] In the following the invention will be explained in more detail with reference to the attached schematic drawings. [Brief description of the drawings]

[0055] [Figure 1] FIG. 1 illustrates one embodiment of an intracardiac medical device, ILP, within a cross-section of a patient's heart. [Diagram 2] FIG. 2 is a functional block diagram of the ILP shown in FIG. [Diagram 3] FIG. 2 is an enlarged side view of the ILP of FIG. 1. [Figure 4] 2 is a flow chart of one embodiment of a method of operation of the ILP of FIG. 1.

[0056] The invention is described below with respect to one embodiment of an ILP. FIGURE 1 illustrates such a ventricular leadless pacemaker (ILP) 10 implanted in a heart 20 of a patient 30. The ILP 10 is implanted in a right ventricle 21 of the heart 20 and can be configured to pace this ventricle, sense intrinsic ventricular depolarizations and depolarizations of an atrium (e.g., right atrium 22), and inhibit ventricular pacing in response to the sensed ventricular depolarizations. A programmer (not shown) can be used to program the ILP 10 and retrieve data from the ILP 10 via a wireless communication connection, examples of which are described above. The ILP 10 is one example of an intracardiac medical device. Other embodiments of intracardiac medical devices, such as cardiac monitors, are possible as well.

[0057] In Fig. 2, a functional block diagram of the ILP 10 configured for implantation in the right ventricle 21 (Fig. 1) is shown. The ILP 10 comprises a processing unit 120 with a clock, at least one counter for clock signals, a data memory 122, a pacing signal generator 124, a detection unit with a first detector 126a and at least one second detector 126b, a communication unit 128, and a power source 132. The power source 132 may be electrically connected to one or more of the other components 120, 122, 124, 126a, 126b, 128 (not shown in Fig. 2) and may include a battery, e.g., a rechargeable or non-rechargeable battery. The power source provides electrical energy to all units and components (not explicitly shown in the figures) of the ILP 10, in particular to all units mentioned above, and is therefore electrically connected to these units and components. Similar or identical units and functions may be included in the ILP 10. The units of the medical device of the present disclosure may include any discrete and / or integrated electronic circuit components implementing analog and / or digital circuits capable of generating the functions attributed to the units herein. For example, the units may include analog circuits, such as amplification circuits, filtering circuits, and / or other signal conditioning circuits. The units may also include digital circuits, such as combinational or sequential logic circuits, memory devices, etc. The units may further be realized using dedicated integrated hardware logic circuits. The data memory 122 may include any volatile, non-volatile, magnetic, or electric media described above. The processing unit 120 may further include instructions that, when executed by one or more processing circuits, cause the unit to perform various functions attributed to these units herein. The functions attributed to the units herein may be embodied as one or more processors, hardware, firmware, software, or any combination thereof.The depiction of various features as units is intended to highlight various functional aspects and does not necessarily imply that such units must be realized by separate hardware or software components. Rather, functions associated with one or more units may be performed by separate hardware or software components or integrated within a common or separate hardware or software component. Data memory 122 can store computer-readable instructions that, when executed by processing unit 120, cause processing unit 120 to perform various functions attributed to processing unit 120 herein. Data memory 122 can further store parameters for these functions, such as pacing signal parameters, conditions, and thresholds described above and below. Pacing instructions and pacing signal parameters, conditions, and thresholds can be updated by a programmer using communication unit 128. Communication unit 128 can have an antenna, a coil, and / or a transceiver.

[0058] The processing unit 120 can communicate with the pacing signal generator 124 and the detectors 126a,b, thereby transmitting signals. The pacing signal generator 124 and the first detector 126a are electrically connected to the electrodes 111, 112 of the ILP 10. The first detector 126a is configured to monitor signals from the electrodes 111, 112 to monitor electrical activity of the heart 20. The second detector 126b may be realized as a motion sensor, for example an accelerometer or any other motion sensor as described above. However, an accelerometer-based motion sensor does not necessarily require any connection to the electrodes 111, 112. The motion sensor collects time-dependent motion signals known from the accelerometer and transmits these signals to the processing unit 120, where they may be pre-processed in the same way as the signals of the first detector 126a, as described below. The pacing signal generator 124 is configured to deliver electrical stimulation signals to the ventricle 21 via the electrodes 111, 112.

[0059] The first detector 126a may further include circuitry for acquiring time-dependent electrical signals from the heart, including intrinsic cardiac electrical activity, such as ventricular events, and intrinsic atrial events, if applicable, such as electrical depolarization and repolarization signals. The first detector 126a may filter, amplify, and / or digitize acquired electrical signals of contractions of the heart chambers, and may include support for splitting inputs from the electrodes into multiple channels for subsequent processing by 120. The processing unit 120 may receive the time-dependent signals generated by the first detector 126a, including ventricular events and intrinsic atrial events, if applicable.

[0060] The processing unit 120 can evaluate the electrical signals and can distinguish between ventricular events received from the first detector 126a and intrinsic atrial events, if applicable, and is configured to determine a (time-dependent) actual heart rate corresponding to an actual duration of one cardiac cycle, calculate an expected duration of one cardiac cycle, as well as classify the intrinsic ventricular events in terms of premature ventricular contractions, as described in more detail below. The processing unit 120 can further control the pacing signal generator 124 to deliver electrical stimulation therapy according to one or more therapy programs including pacing parameters, which can be stored in the data memory 122.

[0061] The ILP 10 may include a housing, an anchoring mechanism (tine) 107, an electrode 111 at a first end 10a of the ILP 10, and an electrode 112 near a second end 10b. The electronic components 101 shown in FIG. 2 (see FIGS. 2, 3) are electrically connected to the electrodes 111, 112 for their function. The housing may have a pill-shaped cylindrical form factor in some embodiments. The anchoring mechanism 107 is configured to couple the ILP 10 to the heart 20. The anchoring mechanism 107 may be made of a shape memory material, such as Nitinol. In some embodiments, the anchoring mechanism may couple the ILP 10 to the heart 20 within one of the ventricles of the heart 20. For example, as shown and described herein with respect to FIG. 1, the anchoring mechanism 107 may be configured to anchor the ILP 10 to the heart 20 within the right ventricle 21. Although the ILP 10 includes a plurality of anchoring mechanisms / elements 107 configured to stably engage the ILP 10 to cardiac tissue in the right ventricle, it is contemplated that a pacemaker according to the present disclosure may use other types of anchoring mechanisms to engage cardiac tissue in other ventricles of the patient's heart 20. The housing further includes a catheter engagement coupling 115 at a second end 10b of the ILP 10.

[0062] The ILP 10 may include two electrodes 111, 112, although in other embodiments, three or more electrodes may be included in the pacemaker. As shown in FIG. 3, the electrodes 111, 112 may be spaced apart by a sufficient distance to detect various electrical signals generated by the heart 20, such as P waves generated by the atria and QRS complexes generated by the ventricles. A housing houses the electronic components of the ILP 10. The electronic components may include any discrete and / or integrated electronic circuit components implementing analog and / or digital circuits capable of producing the functionality attributed to the ILP 10 described above.

[0063] The communications unit 128 may enable the ILP 10 to communicate with other electronic devices, such as a programmer or other external patient monitor, for example, to communicate VES statistics to an HCP. In some embodiments, the housing may house a coil and / or antenna for wireless communication. The housing may also include a power source 132.

[0064] The processing unit 120 may be adapted to control the pacing of the right ventricle 21 in a state using a known VDD mode based on intrinsic atrial events, including atrial contractions, and intrinsic ventricular events, including ventricular contractions, if applicable. The counter of the processing unit 120 used to time the AV delay (to provide a ventricular pace signal) can also be used to measure the intrinsic AV delay. The VDD pacing mode may be R-Sync in ILP10. This means that every cycle is synchronized by every ventricular event used (intrinsic ventricular contraction or ventricular pacing). This is also an atrial tracking mode. This means that every sensed atrial contraction can shift the timing. In other words, the VDD is both R-Sync and P-Sync. The timing of the possible next ventricular pacing signal is scheduled based on the most recent ventricular event and the target pacing interval (determined from the target heart rate). A sensed atrial contraction "reschedules" the next pacing signal by initiating an AV interval. The actual heart rate, and therefore the actual duration of one cardiac cycle, is determined from the intrinsic atrial events and, if applicable, from the intrinsic ventricular events and / or from the pacing output from the pacemaker (ILP10). To control pacing, the processing unit has a state determination module 120a (see FIG. 2), which represents part of an algorithm used to dynamically switch between a state operating according to the VDD mode and other states for determining ventricular pacing time and / or rate information depending on the patient's current state and key parameters predetermined by the HCP.

[0065] As indicated above, the state determination module 120a can operate in a VDD mode, which means that it has ventricular events (either intrinsic ventricular contractions or ventricular pacing signals if intrinsic AV conduction is insufficient) track intrinsic atrial contractions. In another state, the ventricular pacing time and / or rate information can be determined using a VVI or VVI-R action in at least one second state, as described in more detail below. A VVI action has pacing that does not consider atrial activity, but is based on a predefined pacing rate. A VVI-R action relies on a second detector signal representing the patient's actual activity to provide a pacing rate. In one embodiment, no atrial tracking is performed in states using a VVI or VVI-R mode. There can also be another state in which the processing unit can resynchronize intrinsic atrial and ventricular events with pacing and return to a state using a VDD mode. There can be additional non-atrial tracking transition states based on a predefined pacing rate, e.g., a resting rate. For example, the pacing rate is ramped up from an initial (actual) heart rate to a predefined pacing rate. The resting rate may be predefined for a particular patient directly or indirectly by input from the HCP and stored in the data memory. When the state determination module 120a switches between different states, the VES classification of the detected ventricular events may be enabled or disabled. For example, the VES classification may be enabled in an atrial tracking state but disabled in a transition state where the pacing rate is ramped up to a predefined pacing rate, in states using VVI or VVI-R behavior, and in states where ventricular pacing is resynchronized to intrinsic atrial activity. The VES classification may additionally be enabled or disabled for different timer modes, for example, enabled when programmed for VDD mode by the HCP but disabled when programmed for VVI or VVI-R mode.

[0066] For example, when using VDD mode, VES classification is enabled and operates as follows: The operation of VES classification is described with respect to FIG.

[0067] The first detector 126a continuously monitors the electrical activity of the heart 20 by means of the electrodes 111, 112 and transmits detected electrical signals (which may be filtered, amplified and / or digitized electrical signals) to the processing unit 120, for example in the form of IEGMs. The processing unit 120 analyzes these electrical signals for the presence or absence of ventricular events. If a ventricular event is detected in the current cardiac cycle (see step 201 in FIG. 4), the ventricular event is analyzed (see step 203 in FIG. 4) to determine whether the detected ventricular event is an intrinsic ventricular event Vi (see box 205 in FIG. 4) or a paced ventricular event Vp (see box 206 in FIG. 4). These ventricular events can be distinguished with respect to their timing and / or their signal shape. Because processing unit 120 controls the pacing, it knows when a pacing signal is applied and can compare the received ventricular event signal to its prediction of a ventricular paced event, Vp. If pacing does not occur within the corresponding cardiac cycle, an intrinsic ventricular event is assumed.

[0068] If the VES classification is not stopped (see below), in the next step 208, the processing unit 120 evaluates whether the intrinsic ventricular event Vi of the current cardiac cycle is a VES event or whether it is a non-VES event (Vs). If the time distance between the current intrinsic ventricular event and the immediately preceding ventricular event meets at least one predefined prematureness criterion described above, the intrinsic ventricular event Vi is considered as a VES event (see box 209 in FIG. 4), otherwise the intrinsic ventricular event is considered as a non-VES event (Vs) (see box 210 in FIG. 4). For example, the RR peak time distance between the detected R peak of the current intrinsic ventricular event and the detected R peak or a similar feature of the immediately preceding ventricular event is evaluated for whether this time distance meets at least one predefined prematureness criterion. For example, the RR peak temporal distance is equal to or less than a prematureness threshold, for example 0.8 times the expected duration of one cardiac cycle.

[0069] In one embodiment, step 218 may take into account whether an atrial event is detected by the first detector 126a and / or the processing unit 120 before the current intrinsic ventricular event and after the previous ventricular event. If so, step 218 classifies the intrinsic ventricular event as a non-VES event (Vs) (box 210). Therefore, in this case, the prematureness criterion does not apply to the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event. If there is no atrial event within this temporal distance, the prematureness criterion applies.

[0070] After classifying an intrinsic ventricular event as a VES event (box 209) or a non-VES event (Vs) (box 210), information about the characteristics of the current intrinsic ventricular event can be used by the processing unit 120 to terminate the classification and adapt the pacing time for the current cardiac cycle and / or the next cardiac cycle. Additionally, a cardiac cycle in which a VES event is detected may not be taken into account for determining the current heart rate, or similarly for determining the current duration of a cardiac cycle. Furthermore, the detected VES events may be stored in the data memory 122 for statistical reasons and / or communicated to an external device using the communication unit 128.

[0071] 4, in one embodiment, the data memory 122 can include a VES counter 122a. For example, if a VES event 209 is detected, the counter can count up by one (see arrow 212). For example, if a non-VES event 210 (Vs) or a ventricular paced event 206 (Vp) is detected, the counter can count down by one (see arrow 213).

[0072] In order to avoid any persistent pattern of VES classification that is unlikely to indicate a true ventricular extra-contraction, the VES counter 122a is compared with a predefined stop threshold, for example with a value of 30 in step 215. If the counted number of the VES counter 122a is equal to or greater than 30, the VES classification is stopped (see step 217 in FIG. 4). Otherwise, the VES classification remains active. If the VES classification is stopped and a comparison of the VES counter 122a with a re-enabling threshold (which may be, for example, 15) in step 215 reveals that the VES counter value is less than this threshold, the VES classification is re-enabled (see step 218 in FIG. 4). Otherwise, the VES classification remains stopped.

[0073] The above-described classification of intrinsic ventricular events as VES and non-VES events (Vs), together with the possibility to disable and re-enable this classification under certain circumstances, allows for more accurate tracking of the patient's heart rate and compensation for premature ventricular contractions during pacing. Information about intrinsic ventricular events can further be used to adapt therapy, for example by providing a different pacing device or different pacing parameters, if a pathological condition related to premature ventricular contractions is observed.

Claims

1. 1. A method of operating an intracardiac medical device (10) within a patient's heart (20), the medical device (10) having a processing unit (120) and a detector (126a), the detector (126a) detecting time-dependent electrical signals, e.g., intracardiac electrograms, from the heart (20) including a ventricular event, the detected electrical signals being transmitted to the processing unit (120), and the processing unit (120) classifying the current intrinsic ventricular event (Vi, 205) in the received electrical signals as a normal ventricular sense (Vs) or a ventricular extrasystole (VES, 209) if a temporal distance between the current intrinsic ventricular event and a immediately preceding ventricular event satisfies at least one predetermined prematureness criterion, or otherwise classifying the current intrinsic ventricular event (Vi, 205) in the received electrical signals as a normal ventricular sense (Vs) or a ventricular extrasystole (VES, 209), or as a non-VES ventricular event (210).

2. 2. The method of claim 1, wherein the prematureness criterion is met when the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event is significantly shorter than the expected duration of one cardiac cycle and / or is less than or equal to a predetermined cardiac cycle prematureness duration threshold.

3. 3. The method of claim 2, wherein the expected duration of a cardiac cycle is the duration of a most recent cardiac cycle that does not have any VES or is the average of the durations of a predetermined number of most recent cardiac cycles that do not have any VES.

4. 2. The method of claim 1, wherein the processing unit (120) stops applying the predetermined prematureness criteria to the temporal distance between the current intrinsic ventricular event (Vi) and the immediately preceding ventricular event and classifies the current intrinsic ventricular event as a non-VES ventricular event (210) if an atrial event is detected in the electrical signals received after the immediately preceding ventricular event and / or if an atrial event is detected at a temporal distance from the current intrinsic ventricular event that is shorter than the duration of the actual cardiac cycle and / or shorter than a predetermined cardiac cycle prematureness duration threshold.

5. 2. The method of claim 1, further comprising at least temporarily suspending or disabling application of the predetermined prematureness criteria to the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event, and classifying the current intrinsic ventricular event as a non-VES ventricular event by the processing unit at least during a period in which at least one predetermined state of a plurality of states is used by the state determination module of the processing unit.

6. 2. The method of claim 1, further comprising at least temporarily suspending or disabling application of the predetermined prematureness criterion to the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event, and classifying the current intrinsic ventricular event as a non-VES ventricular event by the processing unit at least during a period in which the predetermined VES termination criterion is met, for example, by using a VES counter (122a).

7. 2. The method of claim 1, further comprising re-enabling application of a predetermined prematureness criterion to the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event if a predetermined VES re-enabling criterion is met.

8. 1. An intracardiac medical device (10) comprising: a processing unit (120); and a detector (126a) configured to detect time-dependent electrical signals, such as intracardiac electrograms, of a heart (20) including a ventricular event and transmit the detected electrical signals to the processing unit (120), wherein the processing unit (120) is configured to classify a current intrinsic ventricular event (Vi, 205) of the received electrical signals as a ventricular extrasystole (VES, 209) if a temporal distance between the current intrinsic ventricular event (Vi) and a immediately preceding ventricular event satisfies at least one predetermined prematureness criterion, and otherwise classify the current intrinsic ventricular event as a non-VES ventricular event (210).

9. 9. The medical device of claim 8, wherein the processing unit (120) is configured such that the prematureness criterion is met if the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event is significantly shorter than the expected duration of one cardiac cycle and / or is less than or equal to a predetermined cardiac cycle prematureness duration threshold, for example, the expected duration of one cardiac cycle being the duration of a most recent cardiac cycle without any VES or an average of the durations of a predetermined number of most recent cardiac cycles without any VES.

10. 10. The medical device of claim 8, wherein the processing unit is configured to: stop applying the predetermined prematureness criteria to the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event; and classify the current intrinsic ventricular event as a non-VES ventricular event; if the processing unit detects an atrial event in the electrical signals received after the immediately preceding ventricular event and / or if the atrial event is detected at a temporal distance from the current intrinsic ventricular event that is shorter than the duration of the actual cardiac cycle and / or shorter than the predetermined cardiac cycle prematureness duration threshold.

11. 10. The medical device of claim 8, wherein the processing unit is configured to at least temporarily suspend or disable the application of the predetermined prematureness criteria to the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event, and to classify the current intrinsic ventricular event as a non-VES ventricular event by the processing unit at least during a period in which at least one predetermined state of a plurality of states is used by a state determination module of the processing unit.

12. 10. The medical device of claim 8, wherein the processing unit is configured to at least temporarily suspend or disable the application of the predetermined prematureness criterion to the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event, such that the current intrinsic ventricular event is classified by the processing unit as a non-VES ventricular event during at least a period during which the predetermined VES cessation criterion is met, for example by using a VES counter.

13. 10. The medical device of claim 8, wherein the processing unit is configured to re-enable the application of predetermined prematureness criteria to the temporal distance between the current intrinsic ventricular event and the immediately preceding ventricular event if predetermined VES re-enablement criteria are met.

14. A computer program product comprising instructions that, when executed by a processing unit (120), cause the processing unit (120) to perform the steps of the method of any one of claims 1 to 7.

15. A computer readable data carrier for storing a computer program product according to claim 14.

Images