Pacemaker and method of operation thereof

Abstract

The present invention is generally directed to a cardiac pacemaker (10) that remains synchronized with the heart's natural cycle but also provides safe patient support in the event that an atrial rhythm is detected by the implant that prompts suspicion that SVT has occurred. The pacemaker includes a processing unit (120), a detector (126), and a pacing signal generator (124), the detector (126) and the pacing signal generator (124) being electrically connected to the processing unit (120), the processing unit (120) configured to determine ventricular pacing time values ​​and / or ventricular pacing rate values ​​and transmit corresponding pacing information to the pacing signal generator (124) for providing a pacing signal to the patient's heart (20) based on said information. The present invention is further directed to methods of operation of such a pacemaker, respective computer program products, and computer readable data carriers.

Description

[Technical field]

[0001] The present invention is directed 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 affixed to the pacemaker to contract the myocardial chambers (i.e., atria and / or ventricles) and thus pump blood. By doing so, the device replaces and / or regulates the function of the heart's electrical conduction system. One purpose of a pacemaker is to maintain an adequate heart rate because the heart's natural pacemaker is not fast enough or because a block exists in the heart's electrical conduction system. Additionally or alternatively, pacemakers can stimulate different locations within the ventricles to improve ventricular synchronization or provide anti-tachycardia functions to treat life-threatening arrhythmias. Modern pacemakers are externally programmable, allowing a healthcare practitioner (HCP), such as a clinician, to select the optimal pacing mode for an individual patient.

[0003] A conventional pacemaker comprises a control and generator device with a processing unit and power source external to the patient's heart and electrodes implanted within the heart muscle. The electrodes are connected to the device via leads and a header located on the device. In most cases, the device is implanted subcutaneously in the left or right shoulder area on the anterior part of the chest. An implantable intracardiac pacemaker (also known as an implantable leadless pacemaker ILP) is a miniature pacemaker that is fully implanted within the patient's ventricle (V) or atrium (A) and serves as an important development paradigm for future cardiac rhythm management. Alternative or additional functions of conventional or intracardiac pacemakers include providing other electrical or electromagnetic signals to the heart or its surrounding tissues and sensing electrical or electromagnetic signals (e.g., signals from an electrical depolarization field) or other physiological parameters of the heart and / or its surrounding tissues, such as intrinsic (i.e., the heart's natural) atrial or intrinsic ventricular contractions. Due to significantly limited device size, ILPs have smaller battery capacities compared to traditional approaches that uniquely challenge design flexibility to deliver safe and effective bradycardia symptom-correcting therapy contingent on clinically significant product service times.

[0004] The ILP can operate in a VDD pacing mode (i.e., a pacing mode in which the ventricles are stimulated according to the intrinsic atrial signal and AV conduction monitoring). In the VDD mode, the pacemaker synchronizes ventricular pacing with the intrinsic atrial timing by sensing when an atrial contraction (i.e., the intrinsic atrial signal) occurs. The ILP, which is implanted in the right ventricle, can detect atrial contraction information, but with less reliability and accuracy than a dual-chamber conventional pacemaker with leads in the right atrium as well as the right ventricle.

[0005] The pacing function of a conventional cardiac pacemaker or ILP aims to maintain as much synchronization as possible with the heart's natural activity whenever it effectively supports sufficient cardiac output.

[0006] The utilization of single chamber ILPs requires an implant to provide some of the same therapeutic delivery as traditional pacemaker designs. Thus, a new generation of ILPs is desired that incorporates the ability to effectively "do more" than these traditional device equivalents by driving output based on both intraventricular and remotely sensed cardiac activity. As an example, atrial far-field signal sensing needs to be utilized to provide reliable AV synchronous pacing with a single implant in the right ventricle. This needs to be done in a manner that avoids synchronizing to suspected supraventricular tachycardia (SVT) (i.e., abnormally high heart rates originating in the atria or AV node).

[0007] Currently, ILP provides a means to utilize accelerometers to sense remote atrial cardiac activity in support of AV-synchronous VDD-like therapy, but these implementations are unable to recognize SVT-like rhythms.

[0008] Thus, what is needed is a cardiac pacemaker that remains synchronized with the heart's natural cycle but provides safe patient support when an atrial rhythm is detected by the implant that prompts suspicion that SVT has occurred. Similarly, what is needed is a corresponding method of operation of such a pacemaker.

[0009] The above problem is solved by a cardiac pacemaker having the features of claim 1 and an operating method having the features of claim 8 as well as a computer program product having the features of claim 14 and a computer readable data carrier having the features of claim 15.

[0010] In particular, the above problem is solved by a cardiac pacemaker including a processing unit, a detector, and a pacing signal generator, where the detector and the pacing signal generator are electrically connected to the processing unit. The processing unit is further configured to determine a ventricular pacing time value and / or a ventricular pacing rate value, transmit corresponding information to the pacing signal generator, and provide a pacing signal to the patient's heart based on the information. The processing unit further includes an exercise flag reflecting the patient's actual activity, and an actual status of the exercise flag is true during high activity of the patient or false during low and / or zero activity. The detector is configured to capture a time-dependent signal of cardiac activity including intrinsic atrial events or evidence of such events from conducted intrinsic ventricular events of the patient's heart. In the first atrial tracking state, the processing unit is configured to continuously determine an estimated heart rate based on at least one actual intrinsic atrial event or evidence of such an event from a conducted intrinsic ventricular event detected from the received cardiac activity signal, and compare the estimated heart rate to a predetermined validation rate, and if the estimated heart rate is equal to or greater than the validation rate, the processing unit is configured to evaluate an actual status of an exercise flag; - if the estimated heart rate is greater than or equal to the validation rate and the actual status of the exercise flag is true, or if the estimated heart rate is lower than the validation rate, the processing unit is configured to remain in a first atrial tracking state, in which a ventricular pacing time value and / or a ventricular pacing rate value are determined based on the estimated heart rate; If the estimated heart rate is equal to or greater than the validation rate and the actual status of the exercise flag is false, the processing unit is configured to transition to a supraventricular tachycardia state (SVT state), in which the processing unit is configured to ramp up a ventricular pacing time value and / or ramp down a ventricular pacing rate value, respectively, until a first predetermined pacing time threshold and a first predetermined pacing rate threshold are reached, and to discontinue detection of intrinsic atrial events of the patient's heart from the received cardiac activity signal. For example, upon approaching the first predetermined pacing rate threshold (i.e., a resting rate or idle rate), the ventricular pacing rate is ramped down using a decay rate having a nominal fixed decay (e.g., a rate reduced by 0.5 bpm per therapy output cycle) until the first predetermined pacing rate threshold is reached.

[0011] The pacemaker may be a conventional cardiac pacemaker or defibrillator with pacing function using leads or ILPs having the general structure described above and below.

[0012] In the context of the present invention, a processing unit is generally considered to be a functional unit of the pacemaker that interprets and executes instructions, including an instruction control unit and an arithmetic logic unit. The processing unit may include 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 circuits due to small size and extreme power limitations, especially in the case of ILP.

[0013] The processing unit processes the signal data received from the detector, e.g., motion signals and electrical signals detected over time. Thus, the detector may provide more than one signal, and / or there may be more than one detector or one single detector. In particular, the detector may be configured to capture time-dependent signals of cardiac activity (i.e., signaling that may include electrical or electromagnetic, auditory or other inputs that may report myocardial polarization state or other conditions). From these signals, the detector may derive electrical signals, such as an electrical signal associated with the contraction of one of the atria (in the following intrinsic atrial events) and an electrical signal associated with the contraction of the ventricle (in the following intrinsic ventricular events). In the case of an ILP, the intrinsic atrial events may be far-field signals. The detector may further be configured to distinguish between intrinsic atrial events and intrinsic ventricular events.

[0014] The ILP or conventional pacemaker can operate in a first state according to a VDD pacing mode (i.e., a commonly known pacing mode in which the ventricles are stimulated according to atrial activity and AV conduction monitoring). In the VDD mode, the pacemaker synchronizes ventricular pacing with intrinsic atrial events (atrial contractions). The pacemaker can further use the intrinsic ventricular events (ventricular contractions) and / or the ventricular pacing signal to determine a ventricular pacing time value and / or a ventricular pacing rate value. In an ILP implanted in the right ventricle, the atrial contraction information is detected as a far-field signal as described above. The ventricular pacing time value and / or the ventricular pacing rate value are further determined based on an estimated heart rate determined from the cardiac events in the first state as shown below. Alternatively, the processing unit may be operated in a further state of a VVI or VVI-R mode.

[0015] The processing unit may further comprise a counter and a clock (VDD timer). The counter may be used to count the clock signal of the clock. The counter may be started at each sensed atrial or ventricular contraction and may count the clock number signal until the next atrial or ventricular contraction occurs or a ventricular pacing is provided by the pacing signal generator. In a first state, the processing unit may determine an estimated heart rate of the patient from the intrinsic atrial events and, if applicable, the intrinsic ventricular events. The estimated heart rate may be used to determine a ventricular pacing time value and / or a ventricular pacing rate value and provide pacing information, which is a pacing control signal (e.g., a ventricular pacing control signal) reflecting the ventricular pacing time value and / or the ventricular pacing rate value, which may then be transmitted to the pacing signal generator. Additionally, the pacing information may include / reflect synchronization with the intrinsic atrial events determined by the detector. The pacing information may be, for example, information regarding delivery time, as well as amplitude / strength, duration, and morphology information of the delivered pacing signal.

[0016] Based on the pacing information received from the processing unit, the pacing signal generator generates an electrical pacing signal for transfer to the electrode that 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. The pulse shape may also be varied. The information necessary to generate the correct pacing signal is provided by the processing unit based, at least in part, on the ventricular pacing time value and / or the ventricular pacing rate value. In one embodiment, a pacing signal is not determined or transferred to the electrode by the pacing signal generator if an intrinsic ventricular signal is detected within a predefined period of time after a detected intrinsic atrial event (i.e., an inhibited state).

[0017] The pacemaker may have a data memory, which may include any volatile, non-volatile, magnetic or electrical media, such as random access memory (RAM), read only memory (ROM), non-volatile RAM (NVRAM), programmable ROM (e.g., EEPROM), flash memory, or any other memory device. The data memory stores thresholds, values, flags, parameters and conditions described above and below that are required by the processing unit while processing the steps described above and below.

[0018] In addition to the above functions, the at least one detector further includes an accelerometer, a vibration sensor, an acoustic sensor (including an ultrasonic sensor), and / or any other mechanical, electrical and / or magnetic sensor capable of detecting actual patient activity as a function of time (i.e., a patient body motion sensor). Such capability helps to provide dynamic insight into matters related to whether the patient is moving or stationary, such as monitoring changes in body position / posture, sleep state and / or specific mobility / motion conditions. The detector collects the patient activity signals and converts them into electrical signals. In general, the detector can digitize all or part of the detected or measured analog signals, filter them and / or smooth them to reduce signal noise and / or select specific metrics. Some pre-processing steps can also be provided by the detector. The time-dependent motion signals generated by the detector are preferably transmitted directly to a processing unit.

[0019] The pacemaker units and components may be contained within a hermetically sealed housing.

[0020] In one embodiment, the pacemaker comprises electrodes for applying 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., when the pacemaker is a conventional pacemaker), the electrodes may include leads that can be removably connected to respective connectors at the header. When the cardiac pacemaker is an ILP, one electrode may be located at the distal end of the ILP, near a fixation member where the ILP is fixed in the tissue of the patient's heart, e.g., in the internal 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, and may function, for example, as a counter electrode. Furthermore, the electrodes may be adapted to detect intrinsic ventricular and / or intrinsic atrial signals over time by picking up electrical potentials. In this case, the electrodes may be part of the detector of the pacemaker.

[0021] The patient's heart rate is determined continuously or periodically via interval evaluation based at least in part on the intrinsic atrial events detected by the detector. Additionally, the intrinsic ventricular events detected by the detector may be used to determine this estimated heart rate, also at least in part. If no atrial signal is detected in one cycle, a recent estimated heart rate of one or more sufficiently recent previous cardiac cycles may be used as the (actual) estimated heart rate. Additionally or alternatively, the estimated heart rate may be determined as an average of a predetermined number of previous cardiac cycles, or, if applicable, an average of the actual cardiac cycle.

[0022] In the first state, the estimated heart rate determined by the processing unit based on the intrinsic atrial signal is periodically or continuously compared to a predefined validation rate (see below for an example of the validation rate). The test is performed to determine whether SVT is valid or not. If the estimated heart rate is below the validation rate, the processing unit further operates in the first state since SVT does not appear to be present at this time. However, if the estimated heart rate is equal to or greater than the validation rate, the processing unit is configured to evaluate the status of an exercise flag that is either true during high patient activity (e.g., when the patient's detected body movement is equal to or greater than a predefined level of activity) and / or false under low / inactivity conditions (i.e., the patient's movement is below a predefined level of activity), and the processing unit is configured to determine the status of the exercise flag based on a recently detected exercise signal of the detector that reflects the patient's actual activity. If the estimated heart rate is equal to or greater than the validation rate, there is a basis for determining whether SVT is valid or not. Thus, it is checked whether the patient's activity is the cause of the increased estimated heart rate. In response to these additional tests, the processing unit either continues to control pacing using the first state or switches to an SVT state described above and below.

[0023] The motion flag status is set according to the conditions in the first state where the detector motion sensor (e.g., accelerometer) is turned on and used to determine the motion signal. Such a state occurs, for example, when the processing unit is operating in a sensor-driven mode / state (i.e., leadless-specific VDD mode embodiment or VVI-R main "mode switch" sub-state) or when the atrial tracking state is benchmarked to determine whether the tracked rate is correlated with the relevance of patient motion (i.e., subject to interaction with the validation rate) via triggers or periodic checks as described above. The processing unit continuously or periodically determines the patient's actual activity based on the detected actual signal of the motion sensor and uses such collected data to set the status of the motion flag.

[0024] In one embodiment, if in either the mode / state or test condition the sensor rate seen by the accelerometer is equal to or greater than the motion threshold representing "sufficient" patient body motion (i.e., a predefined patient activity level), the patient is considered to be in motion and the motion flag is set to true status. Otherwise, the motion flag is set to false status. The output of the accelerometer used to detect motion spans a range of values ​​that depends entirely on the particular components used and the range of proof-mass motion that is possible with such components. This full range of signaling is then typically digitized using an analog-to-digital converter (ADC), which then establishes a numerical code for the full range of possible proof-mass signal conditions resulting from the motion of the proof-mass. By sampling the digitized values ​​emerging from the ADC, a time series of acceleration values ​​is obtained by the sensor / processing unit, from which the patient motion can be quantified (deriving the cardiac wall motion through appropriate band-pass signaling). In one embodiment, a processing unit or detector periodically samples the signal transmission from this ADC (e.g., one sample per second) for a specified duration (e.g., four samples) and quantifies the ADC value at each of these sample points. Criteria applied by the system can then determine whether the content within the collected samples was indicative of "sufficient" motion. This can be accomplished by a so-called "X out of Y" condition, e.g., three (X) of four (Y) collected motion samples presenting an ADC value greater than that empirically determined through clinical research efforts to demonstrate patient body motion outside of a "resting" condition. The particular number associated with these points will be highly dependent on the sensor selected, its sensitivity as well as the device and clinical context in which it resides.On the other hand, if the sensor rate associated with the accelerometer falls below a motion threshold representing "sufficient" patient body motion (e.g., if 0, 1, or 2 (X) of the 4 (Y) ADC values ​​exceed a threshold above 1 indicating the patient is at rest), the patient is considered inactive and the status of the flag is set to false (e.g., set to an off state). The motion threshold may, for example, typically prove to represent a "slow to moderate walking condition" (i.e., an ADC value threshold that may represent, for example, something on the order of 20% of the full range of possible ADC values, again part and system design dependent). In one embodiment, the value of such a condition may represent, for example, a quantity that is not patient specific and may represent a constant across all devices of a particular configuration deployed in the field. The motion threshold setting here is, in one embodiment, configurable, but remains unchanged once an appropriate value is established.

[0025] In the first state, if the estimated heart rate is greater than or equal to the validation rate and the exercise flag (currently) has a true status, then SVT is not suspected. Thus, in this case, the processing unit operates continuously in the first state, where the first state is referred to as the "tested" first state. After a predetermined period of time, the test is considered expired and the comparison with the validation rate is repeated or re-enabled.

[0026] However, if the estimated heart rate is equal to or greater than the validation rate and the (actual) status of the exercise flag is false, it is assumed that the patient's heart has developed SVT. The processing unit is therefore configured to transition to an SVT state (which may also be referred to as a fading state, and fading to non-tracking may only be a part of the SVT state). In that state, ventricular pacing should not track the intrinsic atrial signal. Rather, in accordance with the present invention, the processing unit is configured to determine a ventricular pacing time value and / or a ventricular pacing rate value independent of the intrinsic atrial signal. For example, the ventricular pacing rate value (delivered therapy rate) is ramped down (e.g., attenuated at a nominal fixed rate of 0.5 bpm per therapy output / cardiac cycle; similarly, the ventricular pacing time / period value can be ramped up), and the initial value may be the most recently determined estimated heart rate (or the ventricular pacing time value corresponding to the estimated heart rate). Determination of the ventricular pacing rate or time value based on intrinsic atrial events is suspended until a first predetermined pacing rate threshold (also referred to as a resting rate, e.g., a rate configurable by the HCP that is likely to represent 60 bpm, or some similar nominal rate well aligned with a minimally active patient state) is reached, and only after a predetermined timeout occurs (i.e., a first predetermined hold-off period that allows termination of SVT). The ventricular pacing rate / time value used during the SVT state is determined (for at least a portion of the SVT state) based on a ramped estimated heart rate (or a similar ramped time value). The rate may also be determined (for different portions of the SVT state) by different sources, depending on whether it is only ramping up to the first predetermined pacing rate threshold (determined by a fixed decay condition in the fading substate) or has determined a "use motion" input from an in-device accelerometer to drive the therapy output.If a decision is made to "not use exercise," then once the first predetermined pacing rate threshold is reached, the rate value sets the ventricular pacing rate value (similarly, the first predetermined pacing time threshold sets the ventricular pacing time value). If a decision is made to "use exercise," then once the first predetermined pacing rate threshold (or the first predetermined pacing time threshold) is reached, the motion-dependent sensor rate value (or motion-dependent sensor time value) drives the ventricular pacing rate value (or equivalently, the ventricular pacing time value), as described below.

[0027] In one embodiment, in an SVT state (referred to as a suspected SVT state), the processing unit is further configured to instruct the detector to discontinue detection of intrinsic atrial events. Thus, the detector can be configured to discontinue monitoring of atrial cardiac activity. Since intrinsic atrial events are not required for the determination of ventricular pacing time or rate values, they do not need to be determined, thus allowing the system to best conserve its limited power / energy resources in delivering therapy. In this and all further embodiments, the SVT state may include or be a suspected SVT state. In other words, the SVT state or the suspected SVT state may include multiple sub-states that act in concert to manage therapy output when atrial tracking is determined to be suboptimal.

[0028] In one embodiment, during an SVT condition, the device is configured to discontinue capturing the time-dependent signal of atrial cardiac activity.

[0029] In one embodiment, in the SVT state, after the ventricular pacing time value and / or the ventricular pacing rate value reach a first pacing time threshold and a first pacing rate threshold (or resting rate RR), respectively, the processing unit is configured to transition to a non-tracking state, in which the processing unit is configured to continue to suspend detection of intrinsic atrial events of the patient's heart from the received cardiac activity signal and / or continue to suspend capture of a time-dependent signal of atrial cardiac activity by the detector. Non-tracking states are, for example, a non-tracking state and a non-tracking state with motion. Thus, in this embodiment, the processing unit is configured to fade to either a non-tracking state or a non-tracking state with motion, in which the atrial sensing input is turned off or remains unmonitored (i.e., not tracked). In one embodiment, these inputs / detections are already turned off when entering the SVT state (e.g., an initial sub-state of the suspected SVT state, fading to a non-tracking state). Whether the no-tracking state or the no-tracking with motion state is used is predefined or user selectable (users include the patient and the HCP), and in the no-tracking state the processing unit is configured to continue to discontinue determining the estimated heart rate from the intrinsic atrial events or to instruct the detector to discontinue detecting the intrinsic atrial events, such that no determination of the estimated heart rate from the intrinsic atrial events is provided, thereby not consuming additional energy. User selectability of the state can be provided by using a no-tracking mode parameter, which can have at least two predefined different values.

[0030] In one embodiment, the processing unit is configured to remain in an SVT state (e.g., including a fading state, a non-tracking state, and / or a non-tracking state with motion) for at least a predefined first hold-off period. The predefined first hold-off period is configurable by the user (and possibly also by the patient) and lasts for a duration of at least 5-15 minutes, whether measured as a pure duration or by cardiac cycle counting that begins when the system first enters an SVT state or reaches a predefined first pacing time threshold (or a predefined first pacing rate threshold) after entering an SVT. This predefined first hold-off period effectively becomes the duration that the system may reside in either a non-tracking state or a non-tracking state with motion before attempting a transition to another downstream system state. If the HCP has configured the system to "not use motion", expiration of the first hold-off period may advance the system to a FindSync state (see below). If the HCP configures the system to "use motion", expiration of the first hold-off period can advance the system to FindSync when the therapy rate matches that defined by the user for FindSync state operation. In one embodiment, in the non-tracking state, the processing unit is configured to operate in VVI mode, and in the non-tracking state with motion, the processing unit is configured to operate in VVI-R mode. Thus, in one embodiment, in the non-tracking state, the processing unit is configured to determine the ventricular pacing time value and / or the ventricular pacing rate value using the VVI behavior when the non-tracking mode parameter has a predetermined first value, or using the VVI-R behavior when the non-tracking mode parameter has a predetermined second value different from the first value. VVI behavior and VVI-R behavior are essentially known to those skilled in the art.

[0031] In one embodiment, the processing unit is configured to determine the ventricular pacing time value and / or the ventricular pacing rate value using the VVI-R behavior based on a recently detected and received motion signal provided by the detector and / or based on an actual status of the motion flag, and to determine the ventricular pacing time value and / or the ventricular pacing rate value using the VVI behavior based on a predetermined second pacing time threshold and a predetermined second pacing rate threshold, respectively. For example, in a non-tracking state (without motion), the ventricular pacing time value is equal to the predetermined second pacing time threshold and / or the ventricular pacing rate value is equal to the predetermined second pacing rate threshold. In a non-tracking state with motion, the ventricular pacing time value can vary between a maximum pacing time value and a minimum pacing time value, and / or the ventricular pacing rate value can vary between a maximum pacing rate value and a minimum pacing rate value, in either case depending on the most recently detected and received motion signal and / or based on the actual status of the motion flag.

[0032] However, in one embodiment, if the motion flag changes during one of the non-tracking states, tracking is not initiated and exit from the non-tracking state is not initiated. In one embodiment, the first pacing time threshold may be equal to or different from the second pacing time threshold. Thus, the first pacing rate threshold may also be equal to or different from the second pacing rate threshold.

[0033] In one embodiment, the selected one of the non-tracking states remains active for a duration of, for example, 15 minutes or more after the last / previous SVT suspected state is realized. Preferably, the duration of the predetermined first hold-off period provides an opportunity for the SVT to terminate and also avoids excessively frequent rate oscillations resulting from any subsequent tracking response of the current SVT that may rapidly drive the ventricular pacing period downward or the ventricular pacing rate value upward to engage with the validation rate. At the same time, it may be important that the validation rate is sufficiently low, for example between 80 bpm (beats per minute) and 90 bpm, to avoid inducing symptoms that may emerge from tracking a non-terminated SVT. After the first hold-off period has expired (and the rate matches the resting rate used during FindSync when in the non-tracking state utilizing motion), the processing unit is configured to nominally enter the FindSync state. There, support for detection of intrinsic atrial events is resumed.

[0034] Alternatively or additionally, in one embodiment, in the non-tracking state, after the ventricular pacing time value and / or the ventricular pacing rate value do not exceed or undercut the first or second pacing time threshold and the first or second pacing rate threshold, respectively, for a predetermined second hold-off period, the processing unit is configured to transition the pacemaker to a state attempting to re-establish atrial synchrony, wherein detection of intrinsic atrial events of the patient's heart from the received cardiac activity signals and / or capture of a time-dependent signal of atrial cardiac activity is resumed and / or at least one AV delay is initiated by at least one detected atrial event and / or the detected atrial event initiates an AV delay in the pacemaker.

[0035] Moreover, in one embodiment, the detector is further configured to capture a time-dependent signal of cardiac activity including intrinsic ventricular events, and the processing unit is configured to synchronize the pacing signal provided by the pacing signal generator with an AV delay in response to a detected intrinsic atrial event in a transition state adopted after leaving the non-tracking state and before entering the first atrial tracking state, and in the transition state, the processing unit is configured to resume detection of intrinsic atrial events of the patient's heart from the received cardiac activity signal and / or capture of the time-dependent signal of atrial cardiac activity.

[0036] In one embodiment, continuation of the tracking state may be provided after synchronizing intrinsic cardiac activity and pacing using the FindSync state described below.

[0037] In one embodiment, the processing unit is configured such that, in a non-tracking state or a non-tracking state with exercise, if the number of consecutive or total transitions to SVT mode within a period (e.g., within a day) is greater than a predetermined or user-selectable threshold, the hold-off period is extended by a predefined or user-selectable additional hold-off period or until a predefined or user-selectable time point, e.g., midnight.

[0038] Alternatively or additionally, the processing unit is configured such that, in the non-tracking state or the non-tracking state with exercise, if a user-selectable maximum daily allowable number of permissible suspected SVT conditions is exceeded, the first hold-off period or the second hold-off period is extended by a predetermined or user-selectable additional hold-off period or until a predefined or user-selectable time point.

[0039] In one embodiment, a consecutive transition to an SVT state is assumed if a transition from the first state to an SVT state (as shown above) occurs again within a predefined return period (e.g., 5 minutes) after the ability to detect synchronous atrial intrinsic events resumes, or alternatively, relative to the time when mode support leaves the no-tracking state or the no-tracking with motion state. The predefined or user-selectable number of consecutive transitions that initiates an additional hold-off period, or the extension of the baseline hold-off period to a predefined or user-selectable time point, can be, for example, 2, 5, 10, or 20. In another embodiment, the extension of the hold-off period is never used.

[0040] In one embodiment, the total number of transitions to SVT state (from the first state) per day can be stored in a data memory to provide the HCP with a sense of how much SVT burden is present. The daily count may be modified if any allowable consecutive count upper limit is reached. Any statistics collected by the pacemaker related to the number of transitions to SVT over a day or days are made available upon follow-up or through a Home Monitoring Service Center (HMSC) remote monitoring means that interfaces with the pacer and requests a specific patient device that collects the data for relaying to a web-accessible database. Thus, the pacemaker may include a communication unit configured to communicate the collected data (e.g., the number of transitions to SVT state) to the patient device. The details of such HMSC support are not specific to the present invention, but it is anticipated that the patient device used to collect data from the deep leadless spacer will utilize electrically conductive galvanic means, impedance means, magnetic induction means and / or acoustic means to communicate with the implant and relay any collected data to a web-accessible database using either a web portal or cellular network technology.

[0041] In one embodiment, after expiration of the first hold-off period or the second hold-off period in the non-tracking state or the non-tracking with motion state, the processing unit is configured to transition directly or indirectly (i.e., after passing through an intermediate state such as a "sensor" state) to a FindSync state, in which the processing unit is configured to synchronize the pacing signal provided by the pacing signal generator with the detected intrinsic ventricular and / or intrinsic atrial events in this transition state adopted after leaving the non-tracking state and before entering the true atrial tracking state, and in the FindSync state, the processing unit is configured to resume detection of intrinsic atrial events of the patient's heart from the received cardiac activity signal and / or capture of a time-dependent signal of atrial cardiac activity. To this end, the processing unit is further configured to capture a time-dependent signal of cardiac activity including the intrinsic ventricular events. Thus, the processing unit is configured to return to the first state (i.e., the atrial tracking state) if the intrinsic atrial events can feasibly support reliable atrial rate tracking through entering the first state. As discussed above, the no-tracking state or the no-tracking with motion state may be extended if the transition from the first state to the SVT state occurs consecutively.

[0042] In one embodiment, in the FindSync state the processing unit attempts to track an atrial detection. A delay in entering the FindSync state may occur if the implant is in a non-tracking state with motion and the holdoff duration times out while the patient is active.

[0043] In one embodiment, in the FindSync state a new timer is started or started. If that timer expires and the implant a) has not been resynchronized (remains in either the FindSync state or the Sensor state - see below), b) has been resynchronized but remains below the validation rate (in the untested atrial tracking state, i.e., in the first state), or c) has been resynchronized and passes the test at the validation rate (in the tested atrial tracking state, i.e., the patient appears active - i.e., in the first state with an active patient), the suspected SVT is considered to have ended.

[0044] In one embodiment, in the FindSync state, if the device is able to resynchronize and track atrial activity, the processing unit resumes normal tracking behavior (i.e., transitions to the first atrial tracking state). Otherwise, the processing unit remains in FindSync (or if motion support is enabled and the sensor rate prevails, the processing unit periodically checks for prevalence of motion state and transitions to sensor-driven behavior). If the processing unit tracks atrial activity and the estimated heart rate determined based on said activity rises above the validation rate again, the same procedure is performed, but the first hold-off period or the second hold-off period may be different, meaning that the same steps are performed again, but the hold-off period is or can be extended as described above.

[0045] In one embodiment, if an atrial intrinsic event is tracked at a high heart rate and the exercise flag is on (i.e., patient activity is detected), the estimated heart rate can reach the upper tracking rate and remain at this rate for more than a predefined number of cardiac cycles or time. The processing unit can then enter another non-tracking state that effectively mimics a VVI / VVI-R mode of operation. Depending on whether rate response is enabled, the processing unit can transition toward an exercise-driven rate (VVI-R) or fade down to a resting rate and transition toward a FindSync state.

[0046] In the above and following description, predetermined values ​​(thresholds) are values ​​that are pre-programmed (stored in data memory) into the pacemaker, and user-selectable values ​​are values ​​that can be changed / adapted to suit the patient's needs by the HCP or patient, for example by using a programmer.

[0047] The above problem is further solved by a method of operating a cardiac pacemaker, comprising a processing unit, a detector and a pacing signal generator, wherein the detector and the pacing signal generator are electrically connected to the processing unit, the processing unit determines a ventricular pacing time value and / or a ventricular pacing rate value, transmits corresponding pacing information to the pacing signal generator to provide a pacing signal to the patient's heart based on the information, and further comprises an exercise flag reflecting an actual activity of the patient, the actual status of the exercise flag being true during high activity of the patient or false during low and / or zero activity, a time-dependent signal of cardiac activity including intrinsic atrial events or evidence of such events from conducted intrinsic ventricular events of the patient's heart is captured by the detector, In a first atrial tracking state, an estimated heart rate is continuously determined based on at least one actual intrinsic atrial event or evidence of such an event from at least one conducted intrinsic ventricular event detected from the received cardiac activity signal, the estimated heart rate is compared to a predetermined validation rate, and if the estimated heart rate is equal to or greater than the validation rate, an actual status of an exercise flag is evaluated; - if the estimated heart rate is greater than or equal to the validation rate and the actual status of the exercise flag is true, or if the estimated heart rate is less than the validation rate, the method continues in a first atrial tracking state in which a ventricular pacing time value and / or a ventricular pacing rate value are determined based on the estimated heart rate; If the estimated heart rate is greater than or equal to the validation rate and the actual status of the exercise flag is false, the method transitions to an SVT state in which a ventricular pacing time value is ramped up and / or a ventricular pacing rate value is ramped down and detection of intrinsic atrial events of the patient's heart from the received cardiac activity signal is discontinued until a first predetermined pacing time threshold and a first predetermined pacing rate threshold are reached, respectively.

[0048] In one embodiment of the method of operation, during SVT conditions, capture of the time-dependent signal of atrial cardiac activity is discontinued.

[0049] In one embodiment of the method of operation, during an SVT condition, detection of intrinsic atrial events (and by the detector) is discontinued.

[0050] In one embodiment of the method of operation, during an SVT state, after the ventricular pacing time value and / or the ventricular pacing rate value reach a first pacing time threshold and a first pacing rate threshold, respectively, the processing unit transitions to a non-tracking state, during which the processing unit continues to suspend detection of intrinsic atrial events of the patient's heart from the received cardiac activity signal and / or continues to suspend capture of a time-dependent signal of atrial cardiac activity by the detector.

[0051] In one embodiment of the operating method, in a non-tracking state, ventricular pacing time values ​​and / or ventricular pacing rate values ​​are determined using a VVI behavior when the non-tracking mode parameter has a predetermined first value, or using a VVI-R behavior when the non-tracking mode parameter has a predetermined second value different from the first value.

[0052] In one embodiment of the operating method, a ventricular pacing time value and / or a ventricular pacing rate value are determined using a VVI-R behavior based on a recently detected and received motion signal provided by the detector and / or based on an actual status of the motion flag, and / or a ventricular pacing time value and / or a ventricular pacing rate value are determined using a VVI behavior based on a predetermined second pacing time threshold and a predetermined second pacing rate threshold, respectively.

[0053] In one embodiment, the second pacing time threshold may be equal to the first predetermined pacing rate threshold.

[0054] In one embodiment of the method of operation, in the non-tracking state, after the ventricular pacing time value and / or the ventricular pacing rate value do not exceed or undercut the first or second pacing time threshold and the first or second pacing rate threshold, respectively, for a predetermined hold-off period, the processing unit transitions the pacemaker to a state attempting to re-establish atrial synchrony, and detection of intrinsic atrial events of the patient's heart from the received cardiac activity signals and / or capture of time-dependent signals of atrial cardiac activity are resumed, and / or a detected atrial event initiates an AV delay in the pacemaker.

[0055] In one embodiment of a method of operation, the processing unit synchronizes the pacing signal provided by the pacing signal generator with the detected intrinsic ventricular and / or intrinsic atrial events in a transition state or FindSync state adopted after leaving the non-tracking state (or after leaving the non-tracking state with motion and progressing through intermediate states between it and FindSync) and before entering the first state (i.e., the true atrial tracking state), and in the FindSync state, the processing unit begins resuming detection of intrinsic atrial events of the patient's heart from the received cardiac activity signals and / or capture of a time-dependent signal of atrial cardiac activity.

[0056] The above-described embodiment of the operating method has the same advantages as the above-described pacemaker. The above-described embodiments of the pacemaker can be implemented in the operating method as well. In this respect, reference is made to the above description of the pacemaker.

[0057] The above methods may, for example, be realized as a computer program comprising instructions (executed by a medical device, in particular on the processor) that, when executed, cause a processing unit (processor) to perform the steps of the above methods, the instructions being a combination of computer instructions and data definitions specified above and below to enable computer hardware to perform a computational or control function, or being syntactic units consisting of declarations and statements or instructions conforming to the rules of a particular programming language and necessary for the solution of a function, task or problem specified above and below.

[0058] Further disclosed is a computer program product comprising instructions, when executed by a processing unit, causing 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 above pacemakers, methods, computer programs and computer program products use algorithmic means to bias CRM synchronous pacing towards non-arrhythmic conditions and thus adapt therapy output to ultimately provide safer patient support. They further provide enhanced clinical control to improve patient / pacemaker interaction based on underlying etiology considerations through configuration support for the level of "hold-off period" applied to maximize patient comfort in VDD-like mode operation and avoid repeated detection of persistent suspected SVT conditions. In addition, they incorporate predictable / controllable responses to SVT that are easily explainable to the HCP / patient. Related statistics can provide insight into frequency, duration and counts of suspected SVT to support improved patient care with subsequent pacemaker / medication adjustments. Furthermore, when paired with targeted HMSC interrogation of pacemaker / patient interaction, the above inventions provide a means to evaluate suspected SVT between scheduled clinical follow-ups.

[0060] The invention will now be described in more detail with reference to the accompanying schematic drawings. [Brief description of the drawings]

[0061] [Figure 1] FIG. 1 illustrates a first embodiment of a pacemaker in a cross-section of a patient's heart. [Diagram 2] FIG. 2 is a functional block diagram of the pacemaker shown in FIG. [Diagram 3] 2 is a flow chart of one embodiment of a method of operation of the pacemaker of FIG. 1.

[0062] The present invention is described below with respect to an ILP, although it may be implemented in a conventional pacemaker or defibrillator with pacing capabilities as well.

[0063] FIGURE 1 shows an exemplary ventricular leadless cardiac 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 is configurable to pace the ventricle, sense intrinsic ventricular depolarizations and depolarizations in 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 to retrieve data from the ILP 10. The ILP 10 is one example of a cardiac pacemaker 10. Other embodiments of the cardiac pacemaker 10 are possible.

[0064] In Fig. 2, a functional block diagram of the ILP 10 configured to be implanted in the 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 detector 126, a communication unit 128, and a power source 132. The power source 132 is electrically connectable to one or more of the other components / units 120, 122, 124, 126, 128 (not shown in Fig. 2) and may include a battery (e.g., a rechargeable or non-rechargeable battery). The power source 132 provides electrical energy to all units and components of the ILP 10 (not explicitly shown in the figure for simplicity), in particular all units mentioned above, and is therefore electrically connected to these units and components. The units included in the ILP 10 are representative of their respective functions. Similar or identical units and functions may be included in the ILP 10. The pacemaker units of the present disclosure may include any discrete and / or integrated electronic circuit components implementing analog and / or digital circuits capable of forming the functions attributed to the units herein. For example, the units may include analog circuits, amplification circuits, filtering circuits, and / or other signal conditioning circuits. The units may also include digital circuits (e.g., combinational or sequential logic circuits), memory devices, etc. The units may also be implemented using dedicated integrated hardware logic circuits. The data memory 122 may include any volatile, non-volatile, magnetic, or electrical media described above. Additionally, the processing unit 120 may include instructions that, when executed by one or more processing circuits, cause the unit to perform the various functions attributed to the 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 different features as units is intended to highlight different 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 can be performed by separate hardware or software components or can be integrated within a common or separate hardware or software component. The data memory 122 can 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 can store parameters for these functions (e.g., pacing signal parameters, values, conditions and thresholds described above and below). The pacing instructions and pacing signal parameters, conditions and thresholds can be updated by a programmer using the communication unit 128. The communication unit 128 can include an antenna, a coil, a patient anatomical interface and / or a transceiver.

[0065] The processing unit 120 is in communication with the pacing signal generator 124 and the detector 126, and is capable of transmitting signals thereto. The pacing signal generator 124 and the detector 126 are electrically coupled to the electrodes 111, 112 of the ILP 10. The detector 126 is configured to monitor signals from the electrodes 111, 112 to monitor electrical activity of the heart 20. Furthermore, the detector 126 may include a motion sensor, such as an accelerometer or any other motion sensor as described above. It is noted that an accelerometer-based motion sensor does not necessarily require connection to the electrodes 111, 112. The motion sensor collects a time-dependent motion signal as described above and transmits the signal to the processing unit 120. The pacing signal generator 124 is configured to deliver an electrical stimulation signal to the ventricle 21 via the electrodes 111, 112. The processing unit 120 may control the pacing signal generator 124 to generate and deliver electrical stimulation to the ventricle 21 via the electrodes 111, 112. The electrical stimulation may include pacing pulses. Processing unit 120 may control pacing signal generator 124 to deliver the electrical stimulation therapy using the pacing information described above and below in accordance with one or more therapy programs including pacing parameters that may be stored in data memory 122. The pacing information is formed by processing unit 120 based on determined ventricular pacing time values ​​and / or ventricular pacing rate values, which are calculated by the processing unit according to actual conditions adopted by the processing unit (see below).

[0066] Detector 126 may further include circuitry for acquiring time-dependent electrical signals (e.g., electrical depolarization and repolarization signals) from the heart including intrinsic cardiac electrical activity such as intrinsic atrial events and, if applicable, intrinsic ventricular events. Detector 126 may filter, amplify, and digitize acquired electrical events of heart chamber contractions. Processing unit 120 may receive the detected intrinsic atrial events and, if applicable, intrinsic ventricular events provided by detector 126.

[0067] The processing unit 120 is capable of evaluating cardiac activity signals including intrinsic atrial events and, where applicable, intrinsic ventricular events received from the detector 126 and is configured to determine an estimated heart rate (which is time-dependent).

[0068] The ILP 10 may include a housing, an anchoring feature, and electrodes 111, 112. The housing may have a pill-shaped cylindrical form factor in some examples. The anchoring feature is configured to connect the ILP 10 to the heart 20. The anchoring feature may be fabricated from a shape memory material, such as Nitinol. In some examples, the anchoring feature may connect the ILP 10 to the heart 20 in one of the chambers of the heart 20. For example, as shown and described herein with respect to FIG. 1, the anchoring feature may be configured to anchor the ILP 10 to the heart 20 in the right ventricle 21. Although the ILP 10 includes multiple anchoring features / elements 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 be engaged to cardiac tissue in other chambers of the patient's heart 20 using other types of anchoring features.

[0069] The ILP 10 may include two electrodes 111, 112, although in other examples, three or more electrodes may be included in the pacemaker. The electrodes 111, 112 may be spaced apart a sufficient distance to be able 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 providing the functionality attributed to the ILP 10 above and below.

[0070] The communication unit 128 allows 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.

[0071] The processing unit 120 can be adapted to control the pacing of the right ventricle 21 in the first state using a known VDD mode based on the intrinsic atrial signal including atrial contractions and the intrinsic ventricular signal including ventricular contractions, if applicable. The counter of the processing unit 120 used to time the AV delay (to provide the ventricular pace signal) can also be used to measure the intrinsic AV delay. The VDD pacing mode can be R-Sync in ILP10. This means that every cycle is synchronized by every ventricular event used (intrinsic ventricular contraction or ventricular pacing). The VDD pacing mode is also an atrial tracking mode. This means that every sensed atrial contraction can shift the timing. In other words, VDD is effectively 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). A sensed atrial contraction "reschedules" the next pacing signal by initiating the AV interval. The estimated heart rate is determined from intrinsic atrial events and, when applicable, from intrinsic ventricular events.

[0072] The method illustrated in FIG. 3 includes controlling the pacing interval source, tracking interval behavior, motion circuit (enable / disable), atrial tracking behavior (atrial sensing enable / disable), and rate decay behavior under various conditions that may occur while the pacemaker is programmed in VDD mode. In the following, the embodiment refers to the processing unit determining a ventricular pacing rate value, but can function similarly with respect to determining a ventricular pacing time value. The ideal behavior in VDD mode is to have the ventricular event (either an intrinsic ventricular contraction or a ventricular pacing signal if intrinsic AV conduction is inadequate) track the intrinsic atrial contraction (intrinsic atrial event). The ventricular pacing rate value is determined based on the estimated heart rate. In one embodiment, the ventricular pacing rate value is equal to the estimated heart rate, and an AV delay is calculated based on the estimated heart rate to allow an intrinsic ventricular contraction to occur before implementing a pace output. If an intrinsic ventricular event occurs before the AV delay timeout, the pacemaker stops the AV delay and waits for the next atrial contraction in the atrial intrinsic signal. When the AV delay timeout occurs, a ventricular pacing signal is delivered. Atrial tracking (untested and tested) is represented in FIG. 3 by 201. When the intrinsic atrial rate induces VDD mode, the estimated heart rate drives the operation of the pacemaker in the atrial tracking state 201. Subject to the condition that the estimated heart rate is greater than or transitions across the validation rate (i.e., 202 in FIG. 3, which may represent a rate of, for example, 85 bpm), the system performs an evaluation to determine whether the apparently increased cardiac demand is due to the patient's physical motion or is the result of an underlying SVT. When the patient is exercising, tracking is desirable but it is undesirable and inappropriate to be affected by the presence of active SVT, which may mean, for example, that VDD mode pacing in the first state continues (i.e., state 201) as long as the estimated heart rate is below the validation rate (again, the rate designated by 202 in FIG. 3). If the estimated heart rate is equal to or greater than the validation rate, the system checks, via triggering or periodicity, whether the exercise flag is on or off.The status of the exercise flag is determined by processing unit 120 using the motion signal, as described above. The motion sensor provides an alternative criterion for determining the source of increased cardiac demand (i.e., from either patient body motion or SVT).

[0073] If the check at the validation rate 201 determines that the increasing atrial rate may be SVT, as indicated by finding the motion flag false even though the heart rate is equal to or greater than the validation rate, the processing unit is instructed to transition to a non-tracking state to avoid tracking the arrhythmia. The first change is that the ventricular pacing rate value, and therefore pacing, is ramped down from the current estimated heart rate to a predetermined first pacing rate threshold (resting rate, see label 204) by switching to an SVT state (see step 203 of FIG. 3). If the resting rate (label 204) is reached, the processing unit continues in a non-tracking state providing VVI behavior (step 205), e.g., the ventricular pacing rate value remains at the resting rate. In steps 203 and 205, atrial detection is disabled and the motion sensor of detector 126 is also disabled. After a predefined or user-selectable hold-off period expires, the processing unit enters a FindSync state (step A of FIG. 3). The hold-off period begins or is triggered when a tracking validity check fails or when a pause rate is reached. The duration of the hold-off period is programmable and / or predefinable and can last 10-20 minutes (e.g., 15 minutes). From the FindSync state, the processing unit can transition back to the first atrial tracking state (also labeled 201 in FIG. 3) if synchronization with an intrinsic atrial event is found to be successful.

[0074] If the HCP selects the option to use the motion sensor as a secondary rate response source, the rate in the SVT state (203) first drops to the resting rate (as indicated by 204 in FIG. 3A) before entering the no-tracking with motion state (206). This behavior ultimately provides VVI-R mode therapy, with the no-tracking with motion state serving as an alternative to the no-tracking state (i.e., state 205, which in contrast provides VVI mode therapy). In the no-tracking with motion state, the atrial sensing system is disabled and the motion sensor is enabled. Since neither of the no-tracking states (i.e., 205 and 206) provide atrial tracking, the upper tracking rate mechanism is irrelevant. When the motion sensor is used (i.e., as in state 206), the maximum pacing rate is the programmed maximum sensor rate (see label 207 in FIG. 3). 3 indicates that the ventricular pacing rate value when operating in state 206 (i.e., VVI-R behavior) receives a driving input from the motion sensor and can then vary between a resting rate (labeled 204) and a maximum sensor rate (labeled 207). The particular rate employed by the pacer within that range depends directly on the patient's level of motion as detected by a motion sensor (e.g., an accelerometer) of detector 126.

[0075] The next state from either no-tracking state (likewise 205 and 206) is the FindSync state (state A in FIG. 3). If the no-tracking state with motion (206) is permitted by processing unit 120, the processing unit will refuse to transition to FindSync (again, state A) until the sensor rate is equal to or less than the resting rate. After a predefined hold-off period has expired, the processing unit will continue in the FindSync state (step A in FIG. 3), as described above. In the FindSync state, the processing unit synchronizes the pacing signal provided by the pacing signal generator by initiating an AV delay following detection of an intrinsic atrial event. Thus, the processing unit attempts to determine an estimated heart rate that forms the basis of the ventricular pacing rate. From the FindSync state, processing unit 120 may continue in the first state (step 201), as described above, subject to robust detection of a reliable estimated heart rate.

[0076] The method illustrated in FIG. 3 includes: 1) tracking validation checks that occur upon transition from an unverified tracking state (a first state in which the estimated heart rate is less than the validation rate) to a verified tracking state (a first state in which the estimated heart rate is equal to or greater than the validation rate or has previously been equal to or greater than the validation rate and the exercise flag is true), and optionally periodic checks in the verified tracking state (described in 5 below); 2) a passing tracking validation check (i.e., the estimated heart rate is equal to or greater than the validation rate or has previously been equal to or greater than the validation rate and the exercise flag is true) allows entry into the validated tracking state, while a failure (the exercise flag is false) causes the implant to ramp down its ventricular pacing rate value to the rest rate; and 3) after the rest rate is reached, an exercise signal is generated. The method includes: determining whether VVI-R or VVI behavior emerges through configuration of the HCP with respect to "use" or "non-use" of nulling (e.g., potentially implemented using a non-tracking mode parameter, which may have a user-selectable first or second value); 4) after a predetermined hold-off time, exiting the state with VVI-R behavior or the state with VVI behavior and the method continues at "A" to begin the process of attempting to re-establish a tracking condition (FindSync state); and 5) periodically, the first state with a validated tracking condition disables itself to allow the pacemaker to re-engage in tracking validation (i.e., repeating the comparison of the estimated heart rate with the validation rate and checking the status of the exercise flag if the estimated heart rate is greater than or equal to the estimated heart rate).

Claims

1. A cardiac pacemaker (10) comprising a processing unit (120), a detector (126), and a pacing signal generator (124), The detector (126) and the pacing signal generator (124) are electrically connected to the processing unit (120). The processing unit (120) is configured to determine ventricular pacing time values ​​and / or ventricular pacing rate values, transmit corresponding pacing information to the pacing signal generator (124), and provide a pacing signal to the patient's heart (20) based on said information, and further includes an exercise flag that reflects the actual activity of the patient (30), the actual status of which the exercise flag is true during high activity of the patient or false during low activity and / or zero activity, The detector (126) is configured to capture time-dependent signals of cardiac activity, including intrinsic atrial events or evidence of such events, from conductive intrinsic ventricular events in the patient's heart. In a first atrial tracking state (201), the processing unit (120) is configured to sequentially determine an estimated heart rate based on at least one actual endogenous atrial event or evidence of such event from a conducted endogenous ventricular event detected from the received cardiac activity signal, and to compare the estimated heart rate with a predetermined validation rate (202), wherein if the estimated heart rate is greater than or equal to the validation rate (202), the processing unit (120) is configured to evaluate the actual status of the exercise flag. If the estimated heart rate is equal to or greater than the validation rate (202) and the actual status of the exercise flag is true, or if the estimated heart rate is lower than the validation rate (202), the processing unit (120) is configured to remain in the first atrial tracking state (201) in which the ventricular pacing time value and / or the ventricular pacing rate value is determined based on the estimated heart rate. If the estimated heart rate is equal to or greater than the validation rate (202) and the actual status of the exercise flag is false, the processing unit (120) is configured to transition to a supraventricular tachycardia state (SVT state, 203), in which case the processing unit (120) is configured to ramp up the ventricular pacing time value and / or ramp down the ventricular pacing rate value until a predetermined first pacing time threshold and a predetermined first pacing rate threshold (204) are reached, respectively, thereby suspending the detection of intrinsic atrial events in the patient's heart from the received cardiac activity signal. Pacemaker.

2. The pacemaker according to claim 1, wherein in the SVT state (203), the capture of the time-dependent signal of the atrial cardiac activity is interrupted.

3. In the SVT state (203), after the ventricular pacing time value and / or the ventricular pacing rate value reach the first pacing time threshold and the first pacing rate threshold (204), respectively, the processing unit (120) is configured to transition to a non-tracking state (205, 206). In the non-tracking state (205, 206), the processing unit (120) is configured to continue suspending the detection of endogenous atrial events in the patient's heart (20) from the received cardiac activity signal and / or to continue suspending the capture of time-dependent signals of atrial cardiac activity by the detector (126). A pacemaker according to claim 1 or 2.

4. In the non-tracking state (205, 206), the processing unit (120) is configured to determine the ventricular pacing time value and / or the ventricular pacing rate value using VVI behavior (205) when the non-tracking mode parameter has a predetermined first value, or using VVI-R behavior (206) when the non-tracking mode parameter has a predetermined second value different from the first value. The pacemaker according to claim 3.

5. The pacemaker according to claim 4, wherein the processing unit (120) is configured such that the ventricular pacing time value and / or the ventricular pacing rate value are determined using the VVI-R behavior (206) based on recently detected and received motion signals provided by the detector (126) and / or based on the actual status of the motion flag, and the ventricular pacing time value and / or the ventricular pacing rate value are determined using the VVI behavior (205) based on a predetermined second pacing time threshold and a predetermined second pacing rate threshold, respectively.

6. In the non-tracking state (205, 206), after the ventricular pacing time value and / or the ventricular pacing rate value have not exceeded or undercut the first pacing time threshold or the second pacing time threshold and the first pacing rate threshold or the second pacing rate threshold, respectively, over a predetermined holdoff period, the processing unit (120) is configured to transition the pacemaker to a state in which it attempts to re-establish atrial dyssynchrony. Detection of intrinsic atrial events in the patient's heart (20) and / or capture of time-dependent signals of atrial cardiac activity are resumed from the received cardiac activity signal. The pacemaker according to claim 3.

7. The detector (126) is further configured to capture time-dependent signals of cardiac activity, including endogenous ventricular events. The processing unit (120) is configured to synchronize the pacing signal provided by the pacing signal generator (124) using AV delay in response to an endogenous atrial event detected in a transition state (state A) that is adopted after leaving the non-tracking state (205, 206) and before entering the first atrial tracking state (201), In the transition state (back to state A), the processing unit (120) is configured to resume detecting endogenous atrial events in the patient's heart (20) from the received cardiac activity signal and / or capturing the time-dependent signal of the atrial cardiac activity. The pacemaker according to claim 6.

8. A method for operating a cardiac pacemaker (10) comprising a processing unit (120), a detector (126), and a pacing signal generator (124), The detector (126) and the pacing signal generator (124) are electrically connected to the processing unit (120). The processing unit (120) determines a ventricular pacing time value and / or a ventricular pacing rate value, transmits the corresponding pacing information to the pacing signal generator (124), provides a pacing signal to the patient's heart (20) based on the information, and further includes an exercise flag that reflects the actual activity of the patient (30), the actual status of which the exercise flag is true during high activity of the patient or false during low activity and / or zero activity. The detector (126) captures time-dependent signals of cardiac activity, including intrinsic atrial events or evidence of such events, from conductive intrinsic ventricular events in the patient's heart. In the first atrial tracking state (201), an estimated heart rate is successively determined based on at least one actual endogenous atrial event or evidence of such event from at least one conducted endogenous ventricular event detected from the received cardiac activity signal, the estimated heart rate is compared to a predetermined validation rate (202), and if the estimated heart rate is equal to or greater than the validation rate (202), the actual status of the exercise flag is evaluated. If the estimated heart rate is equal to or greater than the validation rate (202) and the actual status of the exercise flag is true, or if the estimated heart rate is lower than the validation rate (202), the method continues in the first atrial tracking state (201) in which the ventricular pacing time value and / or the ventricular pacing rate value is determined based on the estimated heart rate. If the estimated heart rate is equal to or greater than the validation rate (202) and the actual status of the exercise flag is false, the method transitions to an SVT state (203), in which the ventricular pacing time value is ramped up and / or the ventricular pacing rate value is ramped down until a predetermined first pacing time threshold and a predetermined first pacing rate threshold (204) are reached, respectively, and the detection of intrinsic atrial events in the patient's heart from the received cardiac activity signal is interrupted. method.

9. The method according to claim 8, wherein in the SVT state (203), the capture of the time-dependent signal of the atrial cardiac activity is interrupted.

10. In the SVT state (203), after the ventricular pacing time value and / or the ventricular pacing rate value reach the first pacing time threshold and the first pacing rate threshold (204), respectively, the processing unit (120) transitions to a non-tracking state (205, 206). In the non-tracking state (205, 206), the processing unit (120) continues to suspend the detection of endogenous atrial events in the patient's heart (20) from the received cardiac activity signal and / or the detector (126) continues to suspend the capture of time-dependent signals of the atrial cardiac activity. The method according to claim 8.

11. The method according to claim 10, wherein in the non-tracking state (205, 206), the ventricular pacing time value and / or the ventricular pacing rate value is determined using VVI behavior (205) if the non-tracking mode parameter has a predetermined first value, or using VVI-R behavior (206) if the non-tracking mode parameter has a predetermined second value different from the first value.

12. The ventricular pacing time value and / or the ventricular pacing rate value are determined using the VVI-R behavior (206) based on the most recently detected and received motion signal provided by the detector (126) and / or based on the actual status of the motion flag, and / or the ventricular pacing time value and / or the ventricular pacing rate value are determined using the VVI behavior (205) based on a predetermined second pacing time threshold and a predetermined second pacing rate threshold, respectively. The method according to claim 11.

13. In the non-tracking state (205, 206), after the ventricular pacing time value and / or the ventricular pacing rate value have not exceeded or undercut the first pacing time threshold or the second pacing time threshold and the first pacing rate threshold or the second pacing rate threshold, respectively, over a predetermined hold-off period, the processing unit (120) transitions the pacemaker to a state in which it attempts to re-establish atrial dyssynchrony. Detection of intrinsic atrial events in the patient's heart (20) and / or capture of time-dependent signals of atrial cardiac activity are resumed from the received cardiac activity signal. The method according to claim 10.

14. A computer program product that, when executed by a processing unit (120), includes instructions causing the processing unit (120) to perform a step of the method according to any one of claims 8 to 13.

15. A computer-readable data carrier storing the computer program product described in claim 14.

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