Pacemaker and method of operation of such a pacemaker - Patents.com

Abstract

The present invention generally relates to a cardiac pacemaker (10) for a patient's heart (20), the cardiac pacemaker (10) comprising a processing unit (120) having a data memory (122), and further comprising a first detector (126a) electrically connected to the processing unit (120), at least one second detector (126b) electrically connected to the processing unit (120), and a pacing signal generator (124) electrically connected to the processing unit (120), the first detector configured to detect time-dependent electrical signals of the heart, and the at least one second detector (126b) electrically connected to the processing unit (120), is configured to detect a time-dependent body signal of the patient different from the signal detected by the first detector, and the first detector (126a) and the at least one second detector (126b) are configured to transmit the detected signals, and, if applicable, pre-processed signals, to a processing unit (120), which is configured to process the signals received from the first detector and the signals from the at least one second detector, detect intrinsic atrial events, intrinsic ventricular events and pacing events from the signals received by the first detector, and determine an actual heart rate.

Description

[Technical field]

[0001] The present invention relates generally to cardiac pacemakers and methods of operation of such pacemakers, respective computer program products and computer readable data carriers.

[0002] A cardiac pacemaker (or artificial pacemaker) is a medical device that generates electrical pulses delivered by electrodes connected to or fixed to the pacemaker to contract the myocardial chambers (i.e., atria and / or ventricles) and thereby pump blood. In doing so, the device substitutes for and / or regulates the function of the heart's electrical conduction system. One of the purposes of a pacemaker is to maintain an appropriate heart rate, either because the heart's natural pacemaker is not fast enough or because there is a blockage in the heart's electrical conduction system. Additionally or alternatively, pacemakers can stimulate various sites within the ventricles to improve ventricular synchrony or provide an anti-tachycardia effect, with the goal of treating life-threatening arrhythmias. Modern pacemakers are externally programmable, allowing the HCP to select the pacing mode that is best suited for each individual patient.

[0003] A conventional pacemaker includes a control and generator device with a processing unit and power source located outside the patient's heart and multiple electrodes implanted within the heart muscle. These electrodes are connected via leads and headers placed on the device. In most cases, the device is subcutaneously implanted in the left or right anterior part of the chest. An implantable intracardiac pacemaker (also known as an implantable leadless pacemaker (ILP)) is a miniaturized pacemaker that is implanted entirely within the ventricle (V) or atrium (A) of the patient's heart. ILP is considered the future of cardiac pacing. Alternative or additional functions of conventional or intracardiac pacemakers include providing other electrical or electromagnetic signals to the heart or surrounding tissues of the heart, and sensing electrical or electromagnetic signals (e.g., signals from a depolarizing electric field) or other physiological parameters of the heart and / or surrounding tissues, such as intrinsic (i.e., the heart's natural) atrial contractions or intrinsic (i.e., the heart's natural) ventricular contractions. Due to the high constraints on device size, the battery capacity of ILP is small.

[0004] The pacing function of a conventional pacemaker or ILP aims to remain as synchronized as possible with the heart's natural activity.

[0005] Additionally, it is known that pacemakers use specific programmed rates to deliver paced output therapy to the heart. These specific rates may be achieved by counting a clock signal and comparing it to intervals corresponding to the above-mentioned specific rates. The simplest pacemakers use fixed, typically programmable, rates that meet the patient's needs under most circumstances. It is common to use sensor-derived rates based on demand-correlated measurements such as acceleration. To replace the missing AV conduction signal, AV-synchronous pacemakers attempt to pace the ventricles at a rate corresponding to a detected atrial event (e.g., atrial contraction or depolarization events). By utilizing inputs from other types of sensors, it is also possible to infer physiologically missing cardiac rate electrical signals from other systems in the body (e.g., the brain and baroreceptors).

[0006] The intrinsic rate used by all modern pacemakers is the heart's intrinsic rate. When the intrinsic rate is close to the pacing rate, the refractory period of the heart's conduction pathways tends to block the conduction of intrinsic electrical signals, but when the intrinsic signals are at a rate much faster than the pacing rate, these signals can be conducted and trigger heart chamber contractions. These heart chamber contractions are sensed by the pacemaker, and such sensing detection is used to inhibit pacing.

[0007] The primary goal of leadless pacemakers is to provide similar support for bradycardia management as has been provided in conventional pocket leaded IPGs, but in a device that is approximately 10% the size of the total volume of the conventional format. This miniaturization allows the placement of the leadless implant within the patient's cardiac blood volume, reducing the risk of regurgitation and infection by eliminating leaded interfaces with the myocardium, but the ability to directly measure cardiac signaling originating from multiple cardiac chambers (except in configurations that leverage wireless networking with other separate implants) is lost with this approach, as each leadless spacer is entirely contained within a single cardiac chamber. This change in design paradigm therefore creates a need for the implant to collect cardiac chamber information that is readily available to "distant" leaded systems in leadless embodiments (as well as in non-networked leadless pacemaker systems) in cases where synchronous mode support is desired. This capability requires that the affiliate mode support architecture provide an effective means of managing behavior given the resulting reduced reliability of signaling and event detection quality originating from chambers other than the one housing the implant.

[0008] Currently available leadless pacing systems that are placed in the right ventricle and provide AV synchronous therapy output collect “distant” atrial event signaling using a mechanical input from an on-board accelerometer. By using a mechanical input to assess atrial signaling, the device's VDD-style mode support necessarily requires that the implant also maintain the accelerometer in an on-state while running its own mode management timer model. In addition to this mechanical input configuration providing limited fidelity in assessing cardiac events in the atria, such an approach imposes limitations on the maximum accessible upper tracking rate due to the inherent delay associated with the lapse of time between the electrical depolarization action and the resulting mechanical contraction in the heart chamber. Furthermore, the current consumption required to simultaneously operate the timer model management and the on-board accelerometer significantly increases the device's baseline current consumption (from 1.3 μA to 1.6 μA), threatening the device lifespan of the implant where replacement / addition of therapy support becomes complicated and arguably controversial.

[0009] Therefore, a cardiac pacemaker is desired that addresses the unreliable detection of intrinsic atrial events and manages output in response to the changing metabolic needs of the patient. Furthermore, particularly in the case of ILP, pacemakers must meet the challenge of supporting bradycardia symptom management given the severe power budget limitations imposed by conventional device designs.

[0010] The above mentioned problem is solved by a cardiac pacemaker having the features of claim 1, by a method for operation of a cardiac pacemaker having the features of claim 7, by a computer program product having the features of claim 14 and by a computer readable data carrier having the features of claim 15.

[0011] In particular, the above mentioned problem is solved by a cardiac pacemaker for a patient's heart, comprising a processing unit having a data memory, a first detector electrically connected to the processing unit, at least one second detector electrically connected to the processing unit, and a pacing signal generator electrically connected to the processing unit, the first detector being configured to detect a time-dependent electrical signal of the heart, e.g. an intracardiac electrocardiogram, the at least one second detector being configured to detect a time-dependent body signal of the patient, different from the signal detected by the first detector, the first detector and the at least one second detector being configured to transmit the detected signal, and, if applicable, a pre-processed signal, to the processing unit. the processing unit is configured to process the signals received from the first detector and the signals from the at least one second detector, to detect intrinsic atrial events, intrinsic ventricular events and pacing events (and / or understand a sequence of pacing events) from the signals received by the first detector, and to determine an actual heart rate; the processing unit comprises a state determination module, the state determination module is configured to dynamically select one of the at least one first state, the at least one second state and a third state, and to use the selected state to determine ventricular pacing time and / or rate information to meet an actual or therapeutic need of a patient; in at least one first state, an actual heart rate is determined from the detected intrinsic atrial and / or intrinsic ventricular and / or paced events, and current ventricular pacing time and / or rate information is determined in a VDD mode with atrial tracking based on the determined actual heart rate; in at least one second state, determination of an actual heart rate from the detected intrinsic atrial and intrinsic ventricular events is inhibited, and ventricular pacing time and / or rate information is determined, at least in part, based on signals received from the at least one second detector and / or based on a first predefined pacing rate; in a third state, an actual heart rate is determined from the detected intrinsic atrial events, intrinsic ventricular events and / or pacing events, and ventricular pacing time and / or rate information is determined based on a predefined second pacing rate or the determined actual heart rate depending on the recency of the actual heart rate; The state determination module is configured to switch from one of the above-mentioned multiple states (i.e., at least one first state, at least one second state and a third state) to another state, and a direct switch from the at least one first state to the third state is prohibited depending on the current state and depending on at least one condition of a set of predefined conditions.

[0012] The switching may include switching from at least one first state to at least one second state, switching from at least one second state to a third state, and switching from one first state to the other first state, and switching from one second state to the other second state.

[0013] In one embodiment, the processing unit is configured to process the signals received from the first detector and the signals from the at least one second detector, detect intrinsic atrial events, intrinsic ventricular events, and pacing events from the signals received by the first detector, and determine an actual heart rate together with information regarding the recency of the actual heart rate, wherein the determination of the recency is based on the detected intrinsic atrial and intrinsic ventricular events, and the processing unit is configured to determine and transmit ventricular pacing time and / or rate information to the pacing signal generator for providing a pacing signal to the patient's heart based on the information.

[0014] The actual heart rate is sometimes referred to as the measured intrinsic heart rate, and vice versa.

[0015] The main points of the above description may be the following: having two detectors, one for the heart's electrical signals and the other for the patient's physical / metabolic needs; using a processor within the implant to obtain information from the two detectors for the purpose of facilitating therapy using three timer sub-states; sub-state 1 is an atrial tracking state using the first detector, sub-state 2 is a non-tracking state that may or may not utilize primary input from the second detector, which does not necessarily exclude all input from the first detector, and sub-state 3 is a state that, subject to detection of an atrial event, attempts to re-establish tracking by initiating an AV delay.

[0016] In at least one first state, the state determination module uses a VDD pacing mode, which has a behavior in which the ventricles are stimulated depending on an intrinsic atrial event and depending on the presence or absence of an intrinsic ventricular event. This means that if an intrinsic atrial event is detected within a certain interval (AV interval), ventricular pacing is inhibited, or if an intrinsic ventricular event is not detected within a certain interval, ventricular pacing is triggered. This interval can be extended using a predefined hysteresis. In at least one first state, the state determination module uses atrial tracking, which means that the start of the AV interval is adapted to the detected intrinsic atrial event of each cycle, if this event is detected within a predefined time interval.

[0017] At least one of the second state and the third state may be considered as states that realize a VDD mode sub-state. In one embodiment, the state determination module is configured to determine, in at least one of the second states, the ventricular pacing time and / or rate information using a VVI behavior or a VVI-R behavior, as described in more detail below. The VVI behavior includes pacing that does not consider atrial activity but is based on a predefined pacing rate. The VVI-R behavior provides a pacing rate in response to a signal of a second detector that represents the actual activity of the patient. In the second state, tracking of atrial and / or ventricular events (including intrinsic and pacing events) is turned off since the actual heart rate cannot be determined from these events. This behavior may result in reduced power consumption.

[0018] The third state may be considered as a transition state used by the state determination module to resynchronize the intrinsic atrial and ventricular events and pacing back to at least one first state. Initially, the actual heart rate may be determined based on a second predefined pacing rate stored in the data memory, for example the patient's resting rate. The third state may use a first detector and may detect an intrinsic atrial event / sensing and / or an intrinsic ventricular event / sensing. If an intrinsic atrial event is detected, atrial tracking may be used, where an AV delay derived from the actual heart rate may start from this event to phase shift the pacing, thereby resynchronizing the pacing with the intrinsic events of the patient's heart. Further detection of intrinsic atrial and / or ventricular events may be used to determine the actual or measured intrinsic heart rate and increase its recency (also referred to as recency, as described in more detail below). When pacing is in the correct phase and the actual or measured intrinsic heart rate is sufficiently recent, the state determination module is configured to switch to at least one first state. In other words, the at least one first state is an any atrial tracking state, the at least one second state is a no-atrial tracking state where no intrinsic atrial or ventricular event information is used to initiate an AV delay, and the third state is a resynchronization state where any available atrial information is used to initiate an AV delay, but conditions are still insufficient to achieve consistent atrial tracking. The state determination module switches between these states in the manner described above to meet the patient's needs in pacing.

[0019] In one embodiment, the set of predefined conditions includes the following conditions: - the recency of the actual or measured intrinsic heart rate; Comparison of your actual heart rate with a predefined upper rate threshold or a predefined lower rate threshold; a signal received from at least one second detector; and Comparison of the time elapsed from a predefined point in time associated with the switch to the current state with a predefined time interval threshold It contains at least two of the following conditions:

[0020] The rate thresholds mentioned above (also referred to as test rates) can trigger intermediate or transitional states that can use analysis of patient / device interaction to determine how to proceed. One example of this type of test includes support of suspected supraventricular tachycardia (SVT). Here, triggered by the rate threshold, the state determination module can determine whether atrial event input should be further utilized to manage therapy output, or whether other inputs (e.g., motion sensor or baseline low rate) should be utilized to drive pacemaker behavior (conceptually avoiding any tracking of a problematic arrhythmia situation).

[0021] The embodied system may not always be able to determine what is happening in the patient's cardiac system. In such cases, the state determination module may provide a timing pattern that is not necessarily optimal, but is deemed sufficient for all situations, for example, by using a first predefined pacing rate in at least one second state. Furthermore, a timeout may be established to allow the patient / device system to settle into a more typical situation, for example, switching from at least one second state to another second state or a third state, or switching from a third state to at least one first state. Thus, the state determination module may compare the elapsed time from a predefined time point associated with the switch to the current state with a predefined time interval threshold (timeout). When the timeout is reached, the embodiment transitions to a sub-state that prompts acquisition of intrinsic timing information in an attempt to re-establish AV synchronization.

[0022] In one embodiment, the recency (or lack of recency) of the actual or measured intrinsic heart rate is used to switch from one state to the other, according to the above definition. Since VDD mode support in at least one first state is centered around the main objective of supporting AV synchronization when there is a relatively reliable intrinsic sensing input, the concept of recency (also referred to as "recent") of the actual heart rate serves the needs of VDD mode support outlined in this disclosure. The new / old status may be determined using a weighted averaging of events and status, using predefined criteria from a circular buffer of inputs, or from an up / down counter that accumulates an average of weighted events / statuses. For example, it is observed whether the actual or measured intrinsic heart rate is determined from the current cardiac cycle or from a preceding cardiac cycle. This is done using an up / down counter that counts up if the actual heart rate is derived from an intrinsic atrial and / or intrinsic ventricular event in the current cycle, and counts down if no intrinsic events were detected in the current cycle. Depending on the value of the counter it is determined whether the calculated heart rate and / or the measured intrinsic or actual heart rate should be considered as the new heart rate or as the old heart rate.

[0023] The actual heart rate can be caused by either an intrinsic rhythm or a paced event. In this design, the beat-to-beat intervals are measured, and separately, intervals from the cardiac cycle are measured, but these are based only on intrinsic timing, not on paced events. This second group of measurements can be taken from cycles in which ventricular pacing occurs, if that pacing occurred after an atrial sense, or after a cycle in which there was ventricular sensing rather than pacing, regardless of whether that pacing occurred after an atrial sense. Thus, the actual heart rate can always be measured, since there is always a ventricular event present in every cardiac cycle, and there is no need to determine whether our heart rate measurement is new or not. However, since the intrinsic heart rate is measured only in cycles that have intrinsic cardiac information, this information may be out of date. To summarize: the strategy is to distinguish between heart rate, which is a property of the heart, and heart rate measurement, which is a property of the system being described, by using the word measurement when talking about the latter, using the phrase intrinsic rate when meaning the rate coming from the sinus node of the heart, and using the phrase heart rate when talking about the actual heart rate that is controlled by the heart or the pacemaker.

[0024] In pacemaker embodiments where direct measurement of atrial signaling is not possible (e.g., when attempting to support VDD therapy with a leadless spacer that is entirely contained within the patient's right ventricle), the pacemaker may not always be able to readily support detection of atrial events as reliably as traditional leaded systems. While the goal of the pacemaker described above is to support VDD behavior as much as possible in at least one first state, it is described that a state determination module of the processing unit dynamically switches between at least one first state and multiple VDD mode sub-states (at least one second state, a third state) to optimize the timing behavior of the pacemaker in response to dynamically detected conditions associated with difficulty in accessing a reliable atrial input.

[0025] This is based on the observation that the pacemaker must essentially provide pacing support at all times if intrinsic cardiac support is not detected. In VDD mode, only ventricular pacing is performed, and in some cases, both atrial and ventricular sensing is performed to detect intrinsic activity. As long as no intrinsic ventricular events are detected, the device must periodically pace the ventricles. In patients for whom this device is intended, there is typically always some intrinsic timing derived from the sinus node of the heart. If the patient's AV conduction system does not function, the sinus (atrial) timing and the pacemaker (ventricular) pace time may become out of sync. In this situation, the goal of the pacemaker described above is to provide regular pacing support in at least one first state, assuming atrial events are detectable, and to provide pacing support in at least one second state, assuming no or no atrial events are detectable (wherein a timing is used that encourages a situation where intrinsic timing is detectable so that in a third state, the intrinsic cardiac activity and the pacing activity can be resynchronized). The third state is optimized for reacquiring intrinsic rhythm information after a period of time when it has been absent, undetectable, or intentionally ignored due to a suspected arrhythmia. When intrinsic rhythm information is available, the pacemaker's goal is to time the ventricular pacing to keep the pacing timing synchronized with the sinus signal, which may be regular or intermittent. As the sinus rate changes, the pacemaker tracks / follows the sinus signaling, which allows the sinus signaling to track and effectively keep the ventricular pacing synchronized.

[0026] Other states in this embodiment cover behavior specific to atrial tracking disengagement when the atrial rate is suspected to be a tachyarrhythmia; replacement of intrinsic timing with a sensor rate that correlates with metabolic needs; sub-state analysis intended to determine which timing situation may provide more appropriate behavior; and support for gradual rate transitions intended to assist in maximizing the likelihood of achieving improved patient comfort.

[0027] The pacemaker may be a conventional cardiac pacemaker or may be an ILP having the general structure as described above. Moreover, generally, these units and components may operate at a time rate or may use a corresponding time interval. Thus, hereinafter, any description of a time interval should be understood to refer to a rate as well, and vice versa.

[0028] In the context of the present invention, the processing unit is generally considered to be a functional unit of the pacemaker that can interpret and / or execute instructions, including a command control unit and an arithmetic logic unit. The processing unit may include 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. Alternatively or additionally, the processing unit may be realized using integrated dedicated hardware logic, especially in cases of ILP due to small size and extreme power limitations. As mentioned above, the processing unit includes a state determination module, which is configured to dynamically select one of at least one first state, at least one second state, and a third state, and use the selected state to determine ventricular pacing time and / or rate information to meet the actual needs of the patient.

[0029] The processing unit processes the signal data received from the first detector, e.g., electrical signals of the patient's heart detected over time. In particular, the first detector is configured to detect time-dependent electrical depolarization and repolarization field signals, such as an electrocardiogram (ECG) or an intracardiac electrocardiogram (IEGM). These signals include signals caused by atrial depolarization (hereafter, intrinsic atrial events) and electrical signals caused by ventricular depolarization (hereafter, intrinsic ventricular events). In the case of ILP, the intrinsic atrial events may be far-field electrical signals. The first detector may pre-process these data, e.g., digitize these signals, filter these signals, and / or amplify these signals.

[0030] The processing unit to which the detector's electrical signal is transmitted perceives intrinsic ventricular and atrial events from the electrical signal, e.g., intrinsic atrial events from P waves and intrinsic ventricular events from QRS complexes. Since the amplitude of the P waves, from which the far field is electrically measured, is very small compared to the near field ventricular signals, a larger amplification can be used in the period of the signal where the P waves are expected than in the time intervals of the QRS and T waves. Alternatively, the electrical signal input provided by the first sensor may be split into two channels (one for the atrium and the other for the ventricle) inside the processing unit, each channel having its own amplification and filtering scheme to detect intrinsic atrial and intrinsic ventricular events, respectively.

[0031] The pacemaker further comprises at least one second detector configured to detect a time-dependent body signal of the patient different from the signal detected by the first detector, i.e. different from the time-dependent electrical signal of the heart. The at least one second detector cannot detect intrinsic atrial and / or intrinsic ventricular events and / or other signals from the electrical signal of the heart, but can detect them from other sources. The second detector may be, for example, an accelerometer, a vibration sensor, an acoustic sensor (including ultrasound), and / or any other mechanical, electrical and / or magnetic sensor capable of detecting the time-dependent activity of the patient (e.g., based on a motion sensor, assessing whether the patient is active, has a certain posture, achieves a certain activity level, etc.). The detector collects the patient activity signals and converts them into an electrical signal. Furthermore, the detector may digitize the analog signals, filter them, and / or smooth them to reduce signal noise and / or extract certain metrics. Several pre-processing steps may be provided by the detector.

[0032] The signal received from the at least one second detector may be used by the state determination module to determine whether a switch from one state to another is necessary depending on the current needs of the patient. This may be achieved, for example, by a motion flag provided by the processing unit that is on if the patient's activity is above a predefined level and is off if the patient's activity is below the predefined level.

[0033] The ILP or conventional pacemaker operates in a VDD pacing mode in at least one first state. In at least one first state, the pacemaker synchronizes ventricular pacing with intrinsic atrial events based on a fixed, predefined AV delay or an AV delay calculated based on the actual heart rate. In an ILP implanted in the right ventricle, atrial contraction information can be detected as a far-field signal, as described above.

[0034] Further, the processing unit may include a counter and a clock. The counter may be used to count the cycles of the clock. The counter may be started at each sensed atrial or ventricular depolarization and may count the number of clock cycles until the next atrial or ventricular depolarization occurs or until a ventricular pacing is provided by the pacing signal generator. In at least one first state using a VDD mode with atrial tracking, the processing unit uses the most recently detected ventricular event to determine the actual heart rate, thereby continuously adapting to the patient's situation, where if no intrinsic atrial and / or ventricular event is detected in one cycle, the actual or measured intrinsic heart rate does not change with respect to the most recently determined value. For example, in at least one first state, the processing unit may determine the RR interval of the actual cardiac cycle from the intrinsic atrial and intrinsic ventricular or ventricular pacing events. Alternatively, the "current (average) RR interval" may be determined as the average of a predefined number of preceding RR intervals of preceding cardiac cycles and the RR interval of the actual cardiac cycle, which may be weighted. In one embodiment, the RR interval of the actual or measured intrinsic cardiac cycle is used only if at least one intrinsic event (intrinsic atrial and / or intrinsic ventricular event) was used to determine the RR interval of each cardiac cycle (i.e., the qualified RR interval). The actual heart rate may be determined to match the current (average) RR interval or the RR interval of the actual cardiac cycle.

[0035] In a third state, if any intrinsic atrial or ventricular events are detected for each cardiac cycle, the actual or measured intrinsic heart rate is determined as well. If the actual or measured intrinsic heart rate is too old, i.e., the recency of the actual heart rate is below a predefined threshold, the actual or measured intrinsic heart rate is not used in determining the ventricular pacing time and / or rate information, and a predefined second pacing rate is used.

[0036] As described above, in at least one of the first and third states, ventricular pacing time and / or rate information may be determined from the actual or measured intrinsic heart rate. It is described that the actual heart rate, and thus the pacing time and / or rate information, are continuously adapted to the patient's cardiac cycle situation, thereby supporting synchronization of pacing and the heart's intrinsic activity even during cycles in which no intrinsic atrial events are detected.

[0037] In at least one second state, the ventricular pacing time and / or rate information may be determined, at least in part, from the signal of the at least one second detector and / or based on a predefined pacing rate, e.g., a resting rate. This includes embodiments that use a pacing rate that is increased from an initial (actual) heart rate to a predefined pacing rate, e.g., a resting rate or a motion sensor rate. The resting rate may be predefined for a particular patient by input from the HCP, directly or indirectly, and stored in a data memory.

[0038] "Ventricular pacing time and / or rate information" includes any timing information necessary for the pacing signal generator to generate a ventricular pacing signal at the correct time, i.e., in accordance with a therapy plan. The ventricular pacing time and / or rate information may be determined or dictated, in part, by the AV delay and / or heart rate and / or cardiac cycle duration. In one embodiment, the ventricular pacing time and / or rate information may include a hysteresis time that is added to the AV delay or cardiac cycle duration so that pacing is slightly delayed to induce an intrinsic ventricular event.

[0039] Based on the pacing control signal, the pacing signal generator generates an electrical pacing signal for delivery to the electrode, which applies the signal to the cardiac tissue adjacent to the electrode. The pacing signal is a pulse beginning at a desired time and having a desired intensity and duration. Furthermore, the pulse shape may vary. 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 therapeutic output pulse to be administered. In particular, the ventricular pacing control signal includes ventricular pacing time and / or rate information. In one embodiment, provided that no atrial event is detected in at least one first condition, if an intrinsic ventricular event is detected within a predetermined period (i.e., AV delay) after an intrinsic atrial event or an intrinsic ventricular event detected within a predetermined period (i.e., a general rate interval), no pacing signal is determined (i.e., inhibited) or delivered to the electrode.

[0040] The pacemaker may include a data memory, which may include any volatile, non-volatile, magnetic or electrical medium, such as random access memory (RAM), read only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory or any other memory device. The data memory stores the thresholds and conditions mentioned above and below, which are required by the processing unit during the processing of the steps described above and below.

[0041] The pacemaker may further comprise a module such as a communication unit for communicating with a remote computer and a power source such as a battery. The communication unit may exchange messages with an external (at least partially outside the body) remote computer, for example unidirectionally or bidirectionally. The communication may be provided wirelessly, through the patient's body, preferably acoustically, conveyed and / or magnetically / inductively coupled and / or through the air, using electromagnetic waves, for example MICS band, Bluetooth, WLAN, ZigBee, NFC, Wibree or WiMAX in the radio frequency domain or IrDA or Free Space Optics (FSO) in the infrared or optical frequency domain, or wired (electrical and / or optical). The remote computer is a functional unit capable of performing substantial calculations including numerous arithmetic and logical operations without human intervention, such as, for example, a personal mobile device (PMD), a desktop computer, a server computer, a cluster / warehouse scale computer, or an embedded system. The pacemaker units and components may be contained in a hermetically sealed housing.

[0042] In one embodiment, the pacemaker comprises electrodes for application of an electrical pacing signal provided by a pacing signal generator. The electrodes are electrically connected to the pacing signal generator via the header of the pacemaker. In one embodiment (i.e., in the case where the pacemaker is a conventional pacemaker), the electrodes may comprise leads that may be removably connected to respective connectors in the header. With respect to the ILP, one electrode may be located at the distal end of the ILP, near a fixation member for fixing the ILP in the tissue of the patient's heart, for example against or in the tissue of the ventricle. The second electrode may be located at the proximal end of the ILP, or in a part of the ILP housing that may, for example, function as a counter electrode. Furthermore, the electrodes may be adapted to detect intrinsic ventricular or intrinsic atrial events in each case over time by picking up electrical potentials. The electrodes may thus be part of the detector of the pacemaker.

[0043] In at least one first state, the pacing mode supported by the pacemaker is VDD with atrial tracking, as described above. This mode assumes that the patient has some form of intrinsic AV conduction disorder, either complete or intermittent. It also assumes that the sinus node is generally normal, and the VDD mode attempts to track the sinus rate to provide AV synchrony. The AV delay may be determined based on the actual heart rate and may be set to the normal time difference between the intrinsic atrial contraction and the intrinsic ventricular contraction or depolarization. From the actual heart rate, the current AV delay may be determined by known calculations or by using a look-up table contained in the data memory. The current AV delay may vary with the actual heart rate, depending on whether a dynamic AV delay or a fixed, predefined AV delay is used.

[0044] The pacemaker according to the above-described embodiment supports VDD behavior in a first state, if possible, and dynamically switches between multiple sub-states (at least one second state, a third state) to optimize the timing behavior of the pacemaker depending on dynamically detected conditions. These states are controlled by a state decision module (hereinafter also referred to as a state machine).

[0045] In one embodiment, the state determination module is configured such that at least one second state of the plurality of second states is an intermediate state to be used after leaving (e.g., shortly after) at least one first state, for example, when SVT is suspected, and in the intermediate state, the ventricular pacing time and / or rate information is determined from increasing the initial heart rate to a first 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 from the at least one first state to the respective second state. As soon as the first predefined pacing rate is reached, the intermediate state transitions to another second state. Such state switching transitions aim to ensure delivery of baseline bradycardia mitigation therapy while also striving to adapt to measurable patient needs, minimize noticeable symptom onset by avoiding abrupt rate changes, and return device / patient interaction to an optimal situation with minimal delay.

[0046] In one embodiment, the state determination module is configured to select one of the at least one second states using signals received from the at least one second detector to determine ventricular pacing time and / or rate information depending on whether the use of each second detector is permitted, for example, by the HCP. This embodiment has the advantage that the HCP can better adapt the operation of the cardiac pacemaker to the needs of the patient. Furthermore, if motion-dependent pacing is not required for the respective patient, the pacemaker can avoid diverting power from its own primary battery chemistry, which has limited capacity, to the operation of the accelerometer. Furthermore, generally, in certain second states where patient motion is tracked, the system is constructed to turn off any ability to monitor atrial input signaling. This increases the life of the power source (battery).

[0047] In one embodiment, the status determination module is configured to compare a predefined cardiac test rate with the actual heart rate, and / or compare a predefined recency value with a value representative of the recency of the actual heart rate, and / or compare a timeout duration with an elapsed period since a predefined point in time, and evaluate whether the actual status still meets the patient's needs or whether the actual status needs to be left as is based on at least one of these comparisons or on signaling from the temporarily activated second detector.

[0048] The above-mentioned object is further achieved by a method of operation of a cardiac pacemaker for a patient's heart, the cardiac pacemaker comprising a processing unit having a data memory, a first detector electrically connected to the processing unit, at least one second detector electrically connected to the processing unit, and a pacing signal generator electrically connected to the processing unit, detecting time-dependent electrical signals of the heart, e.g. an intracardiac electrogram, by the first detector, detecting time-dependent body signals of the patient different from the signals detected by the first detector by the at least one second detector, and transmitting the detected signals, and if applicable pre-processed signals, from the first detector to the at least one second detector. and transmitting the signals received from the first detector and the at least one second detector to a processing unit, the processing unit processes the signals received from the first detector and the at least one second detector, detects intrinsic atrial events, intrinsic ventricular events and pacing events from the signals received by the first detector, and determines an actual heart rate or a measured intrinsic heart rate, the processing unit comprising a state determination module, dynamically selecting one of the at least one first state, the at least one second state and a third state by the state determination module, and using the selected state to determine ventricular pacing time and / or rate information to meet the actual needs of the patient; in at least one first state, an actual heart rate is determined from the detected intrinsic atrial events, intrinsic ventricular events, and / or paced events, and current ventricular pacing time and / or rate information is determined in a VDD mode with atrial tracking based on the determined actual heart rate; in at least one second state, determination of actual heart rate from (detected) intrinsic atrial events, intrinsic ventricular events and / or, if applicable, in one embodiment, pacing events as well is inhibited, and ventricular pacing time and / or rate information is determined, at least in part, based on signals received from the at least one second detector and / or based on a first predefined pacing rate; In a third state, an actual heart rate is determined from the detected intrinsic atrial events, the intrinsic ventricular events and the pacing events, and ventricular pacing time and / or rate information is determined based on a predefined second pacing rate or the determined actual heart rate depending on the recency of the actual heart rate; The state determination module is configured to switch from one of the above-mentioned states to another state, and a direct switch from at least one of the first states to a third state is prohibited depending on the current state and depending on at least one condition of a set of predefined conditions.

[0049] In one embodiment of the method, the processing unit processes signals received from the first detector and signals from the at least one second detector, detects intrinsic atrial events, intrinsic ventricular events and pacing events from the received signals of the first detector, determines an actual heart rate together with information regarding the recency of the actual heart rate, the determination of the recency being based on the detected intrinsic atrial and intrinsic ventricular events, and determines and transmits ventricular pacing time and / or rate information to a pacing signal generator for providing a pacing signal to the patient's heart based on the information.

[0050] As mentioned above, the actual heart rate is sometimes referred to as the measured intrinsic heart rate, and vice versa.

[0051] In one embodiment of the method, the set of predefined conditions includes the following conditions: - the recency of the measured intrinsic or actual heart rate; Comparison of your actual heart rate with a predefined upper rate threshold or a predefined lower rate threshold; a signal received from at least one second detector; and Comparison of the time elapsed from a predefined point in time associated with the switch to the current state with a predefined time interval threshold It contains at least two of the following conditions:

[0052] In one embodiment of the method, at least one second state of the plurality of second states is an intermediate state used by the state determination module after leaving (e.g., shortly after) the at least one first state, and in the intermediate state, ventricular pacing time and / or rate information is determined from increasing the initial heart rate to a first predefined pacing rate.

[0053] In one embodiment of the method, one of the at least one second states using signals received from the at least one second detector is selected by the state determination module to determine ventricular pacing time and / or rate information depending on whether use of each second detector is permitted, for example, by the HCP.

[0054] In one embodiment of the method, in at least one second state, ventricular pacing time and / or rate information is determined by the state determination module using a (eg, nominal) VVI behavior or a VVI-R behavior.

[0055] As described above, in one embodiment, in VDD mode with atrial tracking used in at least one first state to determine ventricular pacing time and / or rate information, the actual heart rate is determined using at least one most recently detected intrinsic atrial event and at least one most recently detected intrinsic ventricular event, thereby continuously adapting to the patient's situation, where if no intrinsic atrial and / or intrinsic ventricular events are detected in a cycle, the actual intrinsic heart rate does not change with respect to the most recently determined value.

[0056] The above-described embodiments of the method of operation have the same advantages as the above-described pacemaker. The above-described embodiments of the pacemaker can be implemented in the same manner. In this regard, reference is made to the above description of the cardiac pacemaker.

[0057] The above-mentioned methods may for example be implemented as a computer program (i.e. represent computer program code) including instructions which, when executed, cause a processing unit (processor) to perform the steps of the above-mentioned method (to be performed by a cardiac pacemaker, in particular a processing unit of a cardiac pacemaker), the instructions being a combination of the specific computer instructions mentioned above and below and data definitions enabling computer hardware to perform a computational or control function, or the instructions being syntactic units consisting of declarations and descriptions or commands necessary for the above-mentioned and below-mentioned specific functions, tasks or problem solutions, conforming to the rules of a specific programming language.

[0058] Further disclosed is a computer program product comprising instructions which, when executed by a processing unit, cause the processing unit to perform the steps of the method defined above. Accordingly, disclosed is a computer readable data carrier storing such a computer program product.

[0059] The cardiac pacemaker, method, computer program and computer program product described above provide an approach to VDD mode support (in at least one first state) that provides switching between multiple sub-modes or sub-states within VDD mode (which behave similarly to different modes, but are all part of a broad umbrella of VDD mode settings), with the range of sub-modes included derived from user configuration settings. This allows the cardiac pacemaker to leverage the clinician's configuration settings as well as input from the pacemaker's surrounding environment to differentiate the use of various power consumption system design attributes and provide therapeutic support tailored to the patient's needs.

[0060] In addition to state machine control of the various submodes, the cardiac pacemaker combines signals from various state sources into a dynamic selector of the timing pattern that best suits the current situation. One aspect is the history-based degree to which the collected intrinsic cardiac timing information derived from atrial and ventricular sensing is relevant. Intrinsic sensing in successive cardiac intervals provides intrinsic rate information, while individual sensing provides fading information (i.e., offset in the cardiac cycle between atrial and ventricular events). Certain cardiac rhythms exhibit irregular timing, which reduces confidence that the calculated timing is accurate. These conditions are logically extracted and become indicators of (average) actual heart rate, fading and recency. At least one second sensor (e.g., accelerometer) measuring external activity also provides information that can increase or decrease confidence in the cardiac condition if the HCP or a detailed algorithm determines it is appropriate for a particular patient. These signals are processed and mapped to triggers that control state transitions, and the calculated rhythms are used to smooth out the missing intrinsic timing information.

[0061] The set of key concepts of interaction addressed by the VDD mode support used in pacemakers, detailed in the following list, acts to balance a number of therapy optimization needs.

[0062] 1.) If atrial sensing is sufficiently reliable and recent (i.e., "fresh"), the VDD mode support will eventually enter and maintain a synchronous tracking state in at least one first state.

[0063] 2.) VDD mode support maintains recent rate history to support therapy output when atrial sensing is occasionally missing and to remain within a synchronous tracking condition in at least one first state.

[0064] 3.) When in a tracking state in at least one first state, the VDD mode support monitors for features indicative of SVT and either continues tracking (if there is no doubt) or transitions to a low-rate idle state to await termination of SVT in at least one second state (via an intermediate state if there is doubt).

[0065] 4.) If atrial sensing is unreliable and the clinician desires to utilize motion input, then in at least one second state VDD mode support is configured such that therapy rate is driven by accelerometer input signaling.

[0066] 5.) If atrial sensing is unreliable and the clinician wishes to avoid using motion input, or if the patient is simply inactive, the VDD mode support may idle at a low rate in at least one second state and attempt resynchronization in a third state.

[0067] 6.) The state determination module manages any and all transitions between a number of stable sub-states with the intent of mitigating large sudden rate changes that would be symptomatic for the patient by using the intermediate states mentioned above.

[0068] 7.) The state determination module further intentionally disrupts sub-state dwells periodically through state transitions aimed at ensuring that the treatment avoids unintentionally “stuck” in a non-ideal situation.

[0069] The invention will now be described in more detail with reference to the accompanying schematic drawings. [Brief description of the drawings]

[0070] [Figure 1] FIG. 1 illustrates an embodiment of a cardiac pacemaker in cross-section of a patient's heart. [Diagram 2] FIG. 2 is a functional block diagram of the pacemaker shown in FIG. [Diagram 3] FIG. 2 is an enlarged side view of the pacemaker of FIG. 1. [Figure 4] 4 is a flow chart of an embodiment of a method of operation of the status determination module of the pacemaker of FIG. 1.

[0071] Hereinafter, the present invention will be described with reference to an ILP, although it may be implemented in a conventional pacemaker as well.

[0072] FIGURE 1 shows an exemplary ventricular leadless pacemaker (ILP) 10 implanted within a heart 20 of a patient 30. The ILP 10 can be implanted within a right ventricle 21 of the heart 20 and configured to pace the ventricle, sense intrinsic ventricular depolarizations and depolarizations of an atrium (e.g., right atrium 22), and inhibit ventricular pacing in response to a sensed ventricular depolarization. A programmer (not shown) can be used to program the ILP 10 and receive data from the ILP 10 via a wireless communication connection, examples of which are described above. The ILP 10 is one example of a cardiac pacemaker 10. Other embodiments of the cardiac pacemaker 10 are possible.

[0073] FIG. 2 shows a functional block diagram of an ILP 10 configured for implantation in the right ventricle 21 (FIG. 1). The ILP 10 comprises a processing unit 120 with a clock, at least one counter of a clock signal, and a data memory 122, a pacing signal generator 124, a detector 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 all units mentioned above, and is therefore electrically connected to these units and components. Similar or identical units and functions may also be included in the ILP 10. The units of the pacemaker of the present disclosure may include any discrete and / or integrated electronic circuit components implementing analog and / or digital circuits capable of producing 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 include digital circuits, such as combinational or sequential logic circuits, memory devices, and the like. The units may further be implemented using integrated dedicated hardware logic circuits. The data memory 122 may include any volatile, non-volatile, magnetic, or electrical media described above. Furthermore, the processing unit 120 may include instructions that, when executed by one or more processing circuits, cause the units 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. The data memory 122 may store computer readable instructions that, when executed by the processing unit 120, cause the processing unit 120 to perform various functions attributed to the processing unit 120 herein. Additionally, the data memory 122 may store parameters for these functions, such as pacing signal parameters, conditions and thresholds described above and below. The pacing instructions and pacing signal parameters, conditions and thresholds may be updated by a programmer using the communication unit 128. The communication unit 128 may include an antenna, a coil, a patient anatomical interface, and / or a communicator.

[0074] The processing unit 120 can communicate with the pacing signal generator 124 and the detectors 126a, 126b, 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 a connection to the electrodes 111, 112. The motion sensor collects time-dependent motion signals as known from the accelerometer and transmits these signals to the processing unit 120, where the signals may be pre-processed in a similar manner to the signals of the first detector 126a, as described hereinafter. The pacing signal generator 124 is configured to deliver electrical stimulation signals to the ventricle 21 via the electrodes 111, 112. The processing unit 120 can control the pacing signal generator 124 to generate and deliver electrical stimuli to the ventricle 21 via the electrodes 111, 112. The electrical stimuli can include pacing pulses. The processing unit 120 can control the pacing signal generator 124 to deliver the electrical stimulation therapy according to one or more therapy programs, which include pacing parameters, which can be stored in the data memory 122.

[0075] The first detector 126a may further include circuitry for acquiring time-dependent electrical signals (e.g., electrical depolarization and repolarization signals) from the heart that include intrinsic cardiac electrical activity, such as intrinsic atrial events and, if applicable, intrinsic ventricular events. The first detector 126a may filter, amplify and digitize acquired electrical signals of heart chamber contractions 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 intrinsic atrial events and, if applicable, the intrinsic ventricular events generated by the first detector 126a.

[0076] The processing unit 120 is configured to evaluate the intrinsic atrial events and, if applicable, the intrinsic ventricular events received from the first detector 126a, and further to determine the actual heart rate (which is time-dependent).

[0077] The ILP 10 may include a housing, tethering and fixation features (teeth) 107, and electrodes 111, 112 at a first end 10a of the ILP 10 and near a second end 10b of the ILP 10. The housing may have a pill-shaped cylindrical form factor in some examples. The tethering and fixation feature 107 is configured to connect the ILP 10 to the heart 20. The tethering and fixation feature 107 may be fabricated from a shape memory material, such as Nitinol. In some examples, the tethering and fixation feature may connect the ILP 10 to the heart 20 within one of multiple chambers of the heart 20. For example, as shown and described herein with respect to FIG. 1, the tethering and fixation feature 107 may be configured to tether the ILP 10 to the heart 20 within the right ventricle 21. Although the ILP 10 includes a plurality of tethering fixation features / elements 107 configured to stably engage the ILP 10 to cardiac tissue within the right ventricle, it is contemplated that a pacemaker according to the present disclosure may be engaged to cardiac tissue in other chambers of the patient's heart 20 using other types of tethering fixation features. The housing further includes a catheter engagement hitch 115 at the second end 10b of the ILP 10.

[0078] The ILP 10 may include two electrodes 111, 112, although in other examples, more than two electrodes may be included in the pacemaker. As shown in FIG. 3, the electrodes 111, 112 may be spaced apart 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. The 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 generating the functions attributed to the ILP 10 described above.

[0079] The communications unit 128 may enable the ILP 10 to communicate with other electronic devices, such as a programmer or other external patient monitor. In some examples, the housing may house a coil and / or antenna for wireless communication. The housing may also include a power source 132.

[0080] The processing unit 120 may be adapted to control the pacing of the right ventricle 21 in the first state using a known VDD mode based on intrinsic atrial events including atrial contractions and, if applicable, intrinsic ventricular events including ventricular contractions. The counter of the processing unit 120 used for time measurement of the AV delay (to provide a ventricular pacing signal) may also be used for measuring the intrinsic AV delay. The VDD pacing mode may be R-Sync in the 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 timing. In other words, the VDD is both R-Sync and P-Sync. The timing of the next potential ventricular pacing signal is scheduled based on the most recent ventricular event and the target pacing interval (determined from the target heart rate). The sensed atrial contraction "reschedules" the next pacing signal by starting the AV interval. The actual heart rate is determined from intrinsic atrial events, from intrinsic ventricular events, if applicable, and / or from the paced output from the pacemaker (ILP10). To control pacing, the processing unit includes a state determination module 120a (see FIG. 2), which represents part of an algorithm used to dynamically switch between a first state, representing a VDD mode, and a number of second states (hereinafter sub-states) to determine ventricular pacing time and / or rate information depending on the patient's current situation and key parameters predefined by the HCP.

[0081] The method illustrated in FIG. 4 illustrates one example of the operation of such a state determination module, which controls the pacing interval source and further references the tracking interval behavior, the operating circuit (enabled / disabled), the atrial tracking behavior (atrial sensing enabled / disabled), and the rate fading behavior under various conditions that may occur while the pacemaker is programmed in VDD mode. The ideal behavior in VDD mode, represented by the first state 201 of the processing unit's state determination module, is to have the ventricular event (either an intrinsic ventricular contraction or a ventricular pacing signal when intrinsic AV conduction is inadequate) track the intrinsic atrial contraction. Depending on the actual heart rate, if an intrinsic ventricular contraction occurs before the AV timeout is provided, the pacemaker stops the AV delay and waits for the next atrial contraction at the intrinsic atrial event. If the AV timeout occurs, the ventricular pacing signal is delivered. Atrial tracking (not tested) is symbolically represented by the first state 201 in FIG. 4 and uses the signal provided by the first detector 126a. If the atrial rate and therefore the actual heart rate starts to rise, the timing system tracks this under the assumption that this represents an increase in cardiac demand due to the patient's activity. The actual heart rate may be the result of SVT, in which case tracking may be undesirable. Thus, the state determination module switches to testing at 202 if the actual heart rate is equal to or greater than a predefined validation rate, which may be, for example, 85 bpm. As long as the actual heart rate is below the validation rate, VDD mode pacing in the first state continues (state 201). If the actual heart rate is equal to or greater than the validation rate, it is further tested in test 202 whether the motion flag is on or off; if activity is detected by the second detector 126b at or above the predefined level, the motion flag is on, and if activity is below the predefined level, the motion flag is off. The state of the motion flag is determined by the processing unit 120 using a motion signal from the second detector 126b (e.g., an accelerometer) as described above.The motion sensor provides a surrogate indicator of increased cardiac demand.

[0082] If the motion flag indicates activity (i.e., the motion flag is on), the heart rate is considered to be at a valid, required rate and tracking behavior continues. This procedure continues with a first state 201', VDD mode and atrial tracking. This state is now considered to have been checked for patient motion to avoid SVT tracking (see step 201' in FIG. 4). After a predefined time interval and / or if the actual heart rate is lower than the resting rate, the first state 201' is left and the state determination module can return to the first state 201.

[0083] In the first (tested) state 201' and the (initial) first state 201, both with atrial tracking, the determined actual heart rate can be further subject to an upper tracking rate, which is a patient-specific rate above which the maximum heart rate is not exceeded, i.e., the paced rate is limited to the programmed upper tracking rate.

[0084] In the first state 201, 201', especially when a predefined maximum rate is used, the ventricular pace is continuously checked for synchronization with the atrial contraction. This is advantageous since cardiac activity may cause asynchronous behavior, resulting in loss of atrial sensing (indicated by "loss of freshness / staleness"). The actual or measured intrinsic heart rate is subject to a continuous freshness check, i.e., whether the actual or measured intrinsic heart rate is fresh or stale, as described below.

[0085] In the atrial tracking state, the continuously measured qualified RR intervals are used to determine the measured intrinsic heart rate, as described above. The measured intrinsic heart rate is considered old if it is based on detected intrinsic atrial and / or intrinsic ventricular events from a previous cycle going back a predefined number of cycles. The processing unit 120 may provide a counter to count the number of cycles without intrinsic atrial and / or intrinsic ventricular events, thereby detecting whether the actually measured intrinsic heart rate is new or old.

[0086] In case of old intrinsic heart rate detected by processing unit 120, state determination module switches from first state 201, 201' (tested atrial tracking state or untested atrial tracking state) to sensor state 204 if the motion sensor is enabled by the HCP as a backup rate control, or to regression to rest state 205 if the motion sensor is not enabled as a backup rate control. In regression to rest state 205, the heart rate is gradually decreased (dropped) to a predefined resting rate. In this state, atrial sensing is ignored. Sensor state 204 and regression to rest state 205 represent second states according to the definition in the general part of this description.

[0087] When the sensor state 204 is active, atrial sensing is ignored as well. The state 204 is substantially based on the VVI-R behavior. When the motion sensor rate drops to the resting rate, the state determination module 120a switches back to the third state (FindSync state 206) and starts monitoring intrinsic atrial activity again. While in the FindSync state 206, a lack of both atrial sensing and AV conduction or an atrial arrhythmia may prevent locking back to the first state 201 tracking the atrium. This may be achieved, for example, by using the resting rate as the pacing rate. Additionally, the first detector 126a is used to detect intrinsic atrial sensing. If an atrial sensing is detected, an AV delay is initiated to phase-shift the pacemaker activity to match the heart activity. If at least two consecutive cycles are found in which either intrinsic atrial or intrinsic ventricular sensing is detected, the intrinsic VV interval and thus the intrinsic heart rate can be measured and used to set ventricular pacing time and / or rate information. If this proves reliable and is checked by some predefined conditions of validity, the state determination module 120a switches to the first state 201 (unchecked atrial tracking). While in 206, the timing system occasionally turns on the motion sensor (briefly switching to checking patient activity (step 207)) to detect whether there is a situation of cardiac demand that is not being met by the FindSync behavior. If this is detected, the state determination module 120a switches to the sensor state 204 until the motion sensor rate returns to a resting state again.

[0088] If the test 202 in step determines that the increase in atrial rate may be SVT (this is done by finding the motion flag off even though the heart rate is equal to or greater than the validation rate), the state determination module 120a goes to a second non-tracking state to avoid tracking the arrhythmia. The state following the test 202 is regression 210 to an SVT state or non-tracking state (second state). In this state, the heart rate drops from the actual heart rate to the resting rate. If the resting rate is reached and the HCP decides not to use motion input for the mode switching condition, the state determination module 120a continues with a non-tracking state 211 that provides VVI behavior (non-tracking state 211 is another second state). In states 210 and 211, atrial detection by the first sensor 126a is disabled, and the second sensor 126b is also disabled according to optional HCP pre-selection, respectively. While the non-tracking state 211 is employed, the processing unit enters the FindSync state 206 (third state) after expiration of a hold-off period, which may be predefined or user selectable. The hold-off period begins or is initiated when a tracking validity check fails or a lower rate is reached. The duration of this period may be programmable and / or 10-20 minutes, preferably 15 minutes. If synchronization with an intrinsic atrial event is successful, the processing unit may continue from the FindSync state 206 to the first state 201.

[0089] If the HCP selects an option to allow the motion sensor to be used as a secondary rate response source, after the resting rate (RR) is reached in the regression to no tracking state 210, another second state, the no tracking with motion state 212, is selected to provide VVIR behavior. In the no tracking with motion state 212, atrial sensing by the first detector 126a is disabled and the second detector 126b (motion sensor) is enabled. If the motion sensor is used, the maximum pacing rate is the programmed maximum sensor rate (MSR).

[0090] The next state after the no-tracking state 211 is the FindSync state 206 (third state), which is entered only after a timeout has expired, as described above. Alternatively, if the system is in the no-tracking with motion state 212, the sensor state 204 is entered after a timeout has expired. After the sensor state 204 is entered, the FindSync state 206 is entered once the sensor-driven pacing rate matches the resting rate. From the FindSync state 206, the state determination module 120a may continue in the first state 201 (untested atrial tracking), as described above.

[0091] The pacemaker's entry point into the state determination module after system initialization and the initiation of pacing is the FindSync state 206. This is symbolically represented in FIG.

[0092] The above-described embodiments of the cardiac pacemaker (ILP10) and respective methods of operation provide a means of utilizing "remote", far-field IEGM inputs (which are known to be less reliable than direct lead measurements) to facilitate VDD mode support capabilities in a standalone leadless pacemaker that largely mimics equivalent therapy capabilities found in traditional leaded pocket IPGs, effectively providing dual chamber therapy from a device that is entirely contained within a single cardiac chamber. Additionally, the outlined VDD mode support architecture has proven less invasive to implant than traditional formats, providing a means for patients with AV block to benefit from a type of device that places a smaller volume of therapy device within the patient's physiology, expanding the provision of state-of-the-art CRM to patient subpopulations beyond those suffering from bradycardia with chronic AF. Additionally, the cardiac pacemaker and method of operation have proven capable of supporting atrial tracking at higher rates because they use electrical means related to myocardial depolarization as opposed to subsequent mechanical features related to atrial contractile response.

Claims

1. A cardiac pacemaker (10) for the patient's heart (20), The cardiac pacemaker (10) comprises a processing unit (120) having a data memory (122), a first detector (126a) electrically connected to the processing unit (120), at least one second detector (126b) electrically connected to the processing unit (120), and a pacing signal generator (124) electrically connected to the processing unit (120), wherein the first detector is configured to detect a time-dependent electrical signal of the heart, and the at least one second detector is configured to detect a time-dependent physical signal of the patient that is different from the signal detected by the first detector, and the first detector (126a) and the at least one second detector (126b) process the detected signal, and if applicable, the pre-processed signal, into the processing unit The processing unit is configured to transmit signals to a nit (120), and the processing unit is configured to process the signals received from the first detector and the signals from the at least one second detector, to detect endogenous atrial events, endogenous ventricular events and pacing events from the signals received by the first detector, and to determine the actual heart rate, wherein the processing unit comprises a state determination module (120a), which is configured to dynamically select one of at least one first state (201, 201'), at least one second state (204, 205, 210, 211, 212) and a third state (206), and to use the selected state to determine ventricular pacing time and / or rate information to meet the actual needs of the patient, - In at least one first state (201, 201'), the actual heart rate is determined from the detected endogenous atrial and / or endogenous ventricular events, and the current ventricular pacing time and / or rate information is determined in VDD mode with atrial tracking based on the determined actual heart rate. - In at least one of the second states (204, 205, 210, 211, 212), the determination of the actual heart rate from the endogenous atrial and endogenous ventricular events is prohibited, and the ventricular pacing time and / or rate information is determined at least in part based on the signal received from the at least one second detector (126b) and / or based on a first predetermined pacing rate. - In the third state (206), the actual heart rate is determined from the detected endogenous atrial events, endogenous ventricular events, and pacing events, and the ventricular pacing time and / or rate information is determined based on a predetermined second pacing rate or the determined actual heart rate, depending on the recency of the actual heart rate. The state determination module (120a) is configured to switch from one of the multiple states to another, and a direct switch from at least one first state to the third state is prohibited depending on the current state and at least one of a predetermined set of conditions. Cardiac pacemaker (10).

2. The processing unit is configured to process the signals received from the first detector and the signals from the at least one second detector, to detect endogenous atrial events, endogenous ventricular events and pacing events from the signals received from the first detector, and to determine the actual heart rate along with information regarding the recency of the actual heart rate, wherein the determination of recency is based on the detected endogenous atrial and endogenous ventricular events, and the processing unit (120) is configured to determine ventricular pacing time and / or rate information to provide a pacing signal to the patient's heart (20) based on the information and to transmit it to the pacing signal generator (124).

3. The aforementioned set of predetermined conditions shall be followed by the following conditions - The accuracy of the actual heart rate, - Comparison of the actual heart rate with a predetermined upper rate threshold or a predetermined lower rate threshold. - The signal received from at least one second detector, and - Comparison of the elapsed time from a predetermined point in time related to the aforementioned switch to the current state with a predetermined time interval threshold. A cardiac pacemaker according to claim 1 or 2, comprising at least two of the following conditions.

4. A cardiac pacemaker according to claim 1 or 2, wherein the state determination module (120a) is configured such that at least one of a plurality of the second states is an intermediate state (205, 210) used after leaving the at least one first state, and in the intermediate state, the ventricular pacing time and / or rate information is determined by raising the initial heart rate to the first predetermined pacing rate.

5. A cardiac pacemaker according to claim 1 or 2, wherein the state determination module is configured to select one of the at least one second state (204, 212) to determine the ventricular pacing time and / or rate information, using the signal received from the at least one second detector (126b) depending on whether the use of each second detector is permitted.

6. The cardiac pacemaker according to claim 1 or 2, wherein the state determination module is configured to determine the ventricular pacing time and / or rate information using VVI behavior or VVI-R behavior in at least one second state (204, 211, 212).

7. A method for operating a cardiac pacemaker (10) for a patient's heart (20), The cardiac pacemaker (10) comprises a processing unit (120) having a data memory (122), a first detector (126a) electrically connected to the processing unit (120), at least one second detector (126b) electrically connected to the processing unit (120), and a pacing signal generator (124) electrically connected to the processing unit (120), wherein the first detector (126a) detects a time-dependent electrical signal of the heart, and the at least one second detector detects a time-dependent physical signal of the patient that is different from the signal detected by the first detector, and the detected signal, if applicable, a pre-processed signal, is processed by the first detector and the at least one second detector ( The signal is transmitted to the processing unit by 126b), and the processing unit processes the signal received from the first detector and the signal from the at least one second detector, detects an endogenous atrial event, an endogenous ventricular event and a pacing event from the signal received by the first detector, and determines the actual heart rate, the processing unit comprises a state determination module which dynamically selects one of at least one first state (201, 201'), at least one second state (204, 205, 210, 211, 212) and a third state, and uses the selected state (206) to determine the ventricular pacing time and / or rate information to meet the actual needs of the patient, - In at least one first state (201, 201'), the actual heart rate is determined from detected endogenous atrial and endogenous ventricular events, and the current ventricular pacing time and / or rate information is determined in VDD mode with atrial tracking based on the determined actual heart rate. - In at least one of the second states (204, 205, 210, 211, 212), the determination of the actual heart rate from the endogenous atrial and endogenous ventricular events is prohibited, and the ventricular pacing time and / or rate information is determined at least in part based on the signal received from the at least one second detector (126b) and / or based on a first predetermined pacing rate. - In the third state (206), the actual heart rate is determined from the detected endogenous atrial events, endogenous ventricular events, and pacing events, and the ventricular pacing time and / or rate information is determined based on a predetermined second pacing rate or the actual heart rate, depending on the recency of the actual heart rate. The state determination module (120a) is configured to switch from one of the multiple states to another, and a direct switch from at least one first state to the third state is prohibited depending on the current state and at least one of a predetermined set of conditions. method.

8. The method according to claim 7, wherein the processing unit processes the signals received from the first detector and the signals from the at least one second detector, detects endogenous atrial events, endogenous ventricular events and pacing events from the signals received from the first detector, determines the actual heart rate together with information regarding the recency of the actual heart rate, the determination of recency being based on the detected endogenous atrial and endogenous ventricular events, and the processing unit (120) determines ventricular pacing time and / or rate information to provide a pacing signal to the patient's heart (20) based on the information and transmits it to the pacing signal generator (124).

9. The aforementioned set of predetermined conditions shall be followed by the following conditions - The accuracy of the actual heart rate, - Comparison of the actual heart rate with a predetermined upper rate threshold or a predetermined lower rate threshold. - The signal received from at least one second detector, and - Comparison of the elapsed time from a predetermined point in time related to the aforementioned switch to the current state with a predetermined time interval threshold. The method according to claim 7, comprising at least two of the following conditions.

10. The method according to claim 7, wherein at least one of the plurality of the second states is an intermediate state used by the state determination module (120a) after leaving the at least one first state, and in the intermediate state (205, 210), the ventricular pacing time and / or rate information is determined by raising the initial heart rate to the first predetermined pacing rate.

11. The method according to claim 7, wherein one of the at least one second state (204, 212) is selected by the state determination module to determine the ventricular pacing time and / or rate information, using the signal received from the at least one second detector (126b), depending on whether the use of each second detector is permitted.

12. The method according to claim 7, wherein in at least one second state (204, 211, 212), the ventricular pacing time and / or rate information is determined by the state determination module using VVI behavior or VVI-R behavior.

13. The method according to claim 7, in the VDD mode with atrial tracking used in the at least one first state to determine the ventricular pacing time and / or rate information, the actual heart rate is determined using the most recently detected atrial event and / or the most recently detected endogenous ventricular event, thereby continuously adapting to the patient's condition, and in a single cycle, if no endogenous atrial event and / or endogenous ventricular event is detected, the actual heart rate does not change with respect to the most recently determined value.

14. A computer program product, When executed by a processing unit, the processing unit (120) is provided with an instruction to perform a step of the method according to any one of claims 7 to 13. Computer program products.

15. A computer-readable data carrier, A computer program product according to claim 14 is stored in Computer-readable data carrier.

Images