Anti-tachycardia pacing implantable medical device

Abstract

An implantable medical device (IMD) for anti-tachycardia pacing (ATP) of a heart is provided that comprises at least a first pair of electrode poles configured to sense electrical signals of the heart and / or to apply electrical pulses to the heart. The IMD comprises a stimulation unit configured to deliver the electrical pulses to the heart via the first pair of electrode poles. The stimulation unit is configured to deliver at least one therapy sequence to the heart, and the therapy sequence comprises at least one electrical pulse. The IMD comprises a detection unit configured to detect the sensed electrical signals, detect events in the sensed electrical signals, analyze time intervals between the events, and detect a tachycardia condition based on the events. The IMD comprises a control unit configured to generate at least one therapy sequence, and to generate at least one parameter based on the events. The stimulation unit is configured to deliver a first therapy sequence comprising at least one electrical pulse to the heart if the detection unit detects a first tachycardia condition based on a plurality of first events. The first therapy sequence is delivered via the first pair of electrode poles. The detection unit is configured to detect at least one intrinsic event of the heart in the sensed electrical signals during the delivery of the first therapy sequence, wherein the intrinsic event indicates that a tachycardia condition is present. The control unit is configured to generate at least a first parameter based on the intrinsic event. The control unit is configured to adjust the first therapy sequence based on the first parameter during the delivery of the therapy sequence, and / or to generate at least one second therapy sequence based on the first parameter.

Description

[0001] Anmelder: BIOTRONIK SE & Co. KG

[0002] Datum: 19.03.2026

[0003] Unser Zeichen: 24.085P-WO

[0004] ANTI-TACHYCARDIA PACING IMPLANTABLE MEDICAL DEVICE

[0005] This invention generally relates to devices and methods for anti-tachycardia pacing (ATP) of the heart.

[0006] Implantable cardioverter-defibrillators (ICDs) are widely used to prevent sudden cardiac death in patients at risk of life-threatening ventricular arrhythmias. These devices deliver two primary therapies: high-energy shocks and anti -tachycardia pacing (ATP). ATP is generally preferred as a first-line therapy for terminating atrial and ventricular tachycardias because it is painless and conserves device battery life compared to shocks. Conventional ATP strategies, such as Burst and Ramp pacing, deliver a predefined sequence of pacing pulses at intervals shorter than the tachycardia cycle length (TCL) in an attempt to interrupt the reentrant circuit responsible for tachycardia.

[0007] A reentrant circuit is a self-sustaining loop of electrical activation in cardiac tissue, in which an excitation wavefront continuously circulates around a pathway and re-enters areas that have recovered excitability, thereby generating repeated tachycardia beats.

[0008] Despite its clinical benefits, conventional ATP has limitations. Current algorithms typically rely on fixed or preprogrammed parameters, such as the number of pulses, coupling intervals, and sequence structure, which are determined by the physician prior to implantation or during follow-up. These settings do not adapt to the dynamic electrophysiological characteristics of tachycardia at the time of therapy delivery. As a result, ATP may fail to terminate tachycardia or, in some cases, accelerate the arrhythmia, necessitating painful shock therapy. Furthermore, repeated unsuccessful ATP attempts can prolong therapy duration and delay defibrillation, increasing patient risk.

[0009] To address these shortcomings, adaptive ATP algorithms have been introduced. However, existing adaptive approaches remain limited in scope and may require multiple iterations to converge on an effective configuration. This can result in prolonged therapy and does not fully exploit the information available from the patient’s response to prior ATP attempts.US Patent 11,134,881 B2 describes a system for detecting an atrial tachyarrhythmia episode that includes a medical device having sensing circuitry configured to receive a cardiac electrical signal from electrodes coupled to the medical device and a processor configured to detect an atrial tachyarrhythmia episode in response to a time duration of the cardiac electrical signal classified as an atrial tachyarrhythmia being greater than or equal to a first detection threshold. The processor is configured to determine if detection threshold adjustment criteria are met based on at least the detected first atrial tachyarrhythmia episode and adjust the first detection threshold to a second detection threshold different than the first detection threshold in response to the detection threshold adjustment criteria being met.

[0010] Accordingly, there is a need for improved methods and systems that dynamically adjust ATP therapy to the patient’s real-time arrhythmic state. In particular, there is a need for approaches that utilize timing information to optimize the configuration of ATP sequences. Such adaptive strategies have the potential to increase the likelihood of tachycardia termination, reduce the number of unsuccessful attempts, and minimize the need for high-energy shocks.

[0011] The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosed subject matter. This summary is not an extensive overview, and it is not intended to identify key / critical elements or to delineate the scope thereof. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

[0012] An implantable medical device (IMD) for anti-tachycardia pacing (ATP) of a heart comprises at least a first pair of electrode poles configured to sense electrical signals of the heart and / or to apply electrical pulses to the heart. The IMD comprises a stimulation unit configured to deliver the electrical pulses to the heart via the first pair of electrode poles. The stimulation unit is configured to deliver at least one therapy sequence to the heart, and the therapy sequence comprises at least one electrical pulse. The IMD comprises a detection unit configured to detect the sensed electrical signals, detect events in the sensed electrical signals, analyze time intervals between the events, and detect a tachycardia condition based on the events. The IMD comprises a control unit configured to generate at least one therapy sequence, and to generate at least one parameter based on the events. The stimulation unit is configured to deliver a first therapy sequence comprising at least one electrical pulse to the heart if the detection unit detects a first tachycardia condition based on a plurality of first events. The first therapy sequence is delivered via the first pair of electrode poles. The detection unit is configured to detect at least one intrinsic event of the heart in the sensed electrical signals during

[0013] 24.085P-WO / / 19.03.2026the delivery of the first therapy sequence, wherein the intrinsic event indicates that a tachycardia condition is present. The control unit is configured to generate at least a first parameter based on the intrinsic event. The control unit is configured to adjust the first therapy sequence based on the first parameter during the delivery of the therapy sequence, and / or to generate at least one second therapy sequence based on the first parameter.

[0014] An intrinsic event according to the invention is for instance an intrinsic tachycardia beat reappearing during delivery of the therapy sequence, therefore during ATP therapy.

[0015] The IMD according to the invention enables the detection of an intrinsic event during ATP delivery, followed by a dynamic adaptation of therapy based on the intrinsic event by adjustment of the first therapy sequence during delivery of the same, and / or by adjustment of the second therapy sequence. The solution according to the invention can lead to improved ATP therapy success by implementing a dynamic optimization of the inter-pulse interval (SISI or S1S2) interval and avoidance of progressing a lost entrainment, while increasing patient safety due to avoiding further tachycardia acceleration.

[0016] An intrinsic event may lead to acceleration of a tachycardia because the intrinsic excitation disrupts the intended entrainment, causing loss of ATP pacing control and fracturing of excitation fronts. This timing scenario allows the reentrant circuit to resume or even shorten its cycle length, enabling intrinsic tachycardia events to reappear more rapidly and potentially destabilizing the rhythm.

[0017] Generally speaking, entrainment is defined as the process of capturing and “over-driving” a reentrant tachycardia circuit by delivering ATP paces that are slightly faster than the tachycardia cycle length with a sufficient number of pulses. When the pacing rate is just faster than the ongoing tachycardia, each paced beat enters the circuit’s excitable gap, drives the circuit at the pacing rate, and can ultimately terminate the tachycardia — typically by causing the paced wavefronts to collide and extinguish within the circuit. It is therefore desirable to provide ATP delivery that can be adapted in response to intrinsic cardiac activity detected during therapy. However, if the ATP pacing interval is set shorter than a critical boundary interval, entrainment may be lost and intrinsic events corresponding to the underlying tachycardia may reappear.

[0018] According to an embodiment of the present invention, the detection unit is configured to detect the intrinsic event via the first pair of electrode poles, or via a second pair of electrode poles. At least one electrode pole of the second pair of electrode poles is different from the electrode poles of the

[0019] 24.085P-WO / / 19.03.2026first pair of electrode poles, which provides flexibility in sensing configurations for detecting the intrinsic event.

[0020] For instance, the first parameter is at least one of the following:

[0021] • A duration of the first and / or second therapy sequence,

[0022] • A number of pulses of the first and / or second therapy sequence,

[0023] • An inter-pulse interval between at least two pulses of the first and / or second therapy sequence, or

[0024] • A coupling interval between the intrinsic event and a pulse of the first therapy sequence.

[0025] These embodiments of the invention provide multiple parameterization options for adapting an ATP therapy sequence in response to the intrinsic event.

[0026] According to an aspect of the invention, the first therapy sequence comprises a plurality of interpulse intervals. The control unit can be configured to adjust the first therapy sequence by prolonging at least one inter-pulse interval of the first therapy sequence. The prolonged inter-pulse interval immediately succeeds the intrinsic event. The prolonged inter-pulse interval is longer than the interpulse interval directly preceding the intrinsic event.

[0027] By adjusting the running therapy sequence, the chances of tachycardia termination can be increased immediately after detection of the intrinsic event.

[0028] According to an embodiment, the first therapy sequence comprises a plurality of inter-pulse intervals. The control unit can be configured to adjust the first therapy sequence by scheduling an electrical pulse that directly succeeds the intrinsic event such that the inter-pulse interval between the electrical pulse that is delivered directly prior to the intrinsic event and the electrical pulse that directly succeeds the intrinsic event is prolonged. The prolonged inter-pulse interval is longer than the interpulse interval that directly precedes the detection of the intrinsic event.

[0029] Said embodiment allows a controlled prolongation of that inter-pulse interval in which the intrinsic event occurs, which additionally increases the chances of tachycardia termination immediately after detection of the intrinsic event.

[0030] According to an aspect of the present invention, the second therapy sequence comprises a plurality of inter-pulse intervals. The control unit can be configured to adjust the second therapy sequence by

[0031] 24.085P-WO / / 19.03.2026prolonging at least one inter-pulse interval of the second therapy sequence. The prolonged inter-pulse interval of the second therapy sequence has a position in the second therapy sequence which is the same position as, the same position minus one, or the same position plus one as the position of the prolonged inter-pulse interval in the first therapy sequence. The prolonged inter-pulse interval of the second therapy sequence is longer than the inter-pulse interval of the first therapy sequence which directly precedes the detection of the intrinsic event.

[0032] The embodiment allows a consistent adjustment across therapy sequences using related interval positions, which increases the chances of tachycardia termination in following ATP attempts after delivery of the first therapy sequence.

[0033] Moreover, according to an embodiment, the control unit is configured to cancel the delivery of the first therapy sequence if the detection unit detects the intrinsic event.

[0034] The detection of the intrinsic event indicates that a tachycardia condition has occurred is still persistent, which leads to the conclusion that the ongoing therapy sequence cannot effectively terminate the tachycardia. Moreover, the one or more intrinsic events disturb the stimulation timing of the ATP therapy sequences, i.e. the intrinsic event can cause a fracturing of the excitation fronts that are generated by the electrical pulses of the therapy sequence, that may cause a ventricular fibrillation in the heart. An immediate cancellation of the therapy sequence can prevent this scenario, and in addition, saves IMD battery life and time for therapy optimization.

[0035] In an embodiment of the present invention, the control unit is configured to generate the first and / or second therapy sequence such that it comprises at least a succession of inter-pulse intervals having a decreasing length. The control unit can be configured to generate no further decrease of an interpulse interval succeeding the detection of the intrinsic event.

[0036] Successively reducing the inter-pulse interval length, also called "ramp", until the intrinsic event occurs enables determining the shortest allowable inter-pulse interval that results effective an ATP therapy. If further shortening of inter-pulse intervals smaller than such boundary interval length is prevented, the effectiveness of the ATP therapy can be increased.

[0037] Moreover, according to an embodiment, the control unit is configured to generate at least one interpulse interval of the first therapy sequence or second therapy sequence that succeeds the detection of the intrinsic event. The at least one inter-pulse interval is of equal length or longer than the shortest

[0038] 24.085P-WO / / 19.03.2026inter-pulse interval that preceded the detection of the intrinsic event and which did not lead to detection of the intrinsic event.

[0039] By establishing that lower bound on inter-pulse intervals for the ATP therapy after the detection of the intrinsic event, the effectiveness of the succeeding ATP attempts can be increased.

[0040] According to an aspect of the present invention, the control unit is configured to store the inter-pulse interval which directly preceded the detection of the intrinsic event in a memory unit. The control unit can be configured to adjust at least one of the first, second or a further therapy sequence such that at least one inter-pulse interval of the therapy sequence is longer than the stored inter-pulse interval.

[0041] For example, a group of said stored inter-pulse intervals is arranged at the beginning of at least one further therapy sequence, which may increase the chances for a fast termination of a tachycardia condition.

[0042] According to an aspect, the control unit is configured to store at least a first tachycardia cycle length of the first tachycardia condition leading to the delivery of the first therapy sequence. The control unit can be configured to generate at least one further therapy sequence if a further tachycardia cycle length is sufficiently similar to the first tachycardia cycle length. The at least one further therapy sequence comprises at least a group of said stored inter-pulse intervals. Enabling a reuse of stored inter-pulse interval parameters based on the similarity of tachycardia cycle lengths may lead to a more effective ATP therapy.

[0043] According to an embodiment, a further tachycardia cycle length is sufficiently similar to the first tachycardia cycle length if the difference between the two tachycardia cycle lengths does not exceed an absolute tolerance, which can be a programmable similarity threshold. Alternatively, the difference shall not be greater than a relative tolerance, e.g. within a certain percentage of the first tachycardia cycle length.

[0044] For instance, the control unit is configured to adjust and / or generate a programmable number of interpulse intervals of the first, second and / or further therapy sequence based on the first parameter, which increases the flexibility of therapy sequence adjustment.

[0045] 24.085P-WO / / 19.03.2026According to an embodiment of the present invention, at least one electrode pole is at least a part of a housing of the IMD, and / or such that at least one electrode pole is located to detect electrical signals from a left ventricle of the heart. These option expand implementation options for electrode integration and / or additional sensing / pacing vectors.

[0046] Moreover, a method for operating an IMD for stimulating a human or animal heart is proposed. The method comprises detecting a first tachycardia condition based on a plurality of first events in an electrical signal of the heart, delivering a first therapy sequence comprising at least one electrical pulse to the heart via a first pair of electrode poles, detecting at least one intrinsic event of the heart in the sensed electrical signals during the delivery of the first therapy sequence, wherein the intrinsic event indicates that a tachycardia condition is present. The method further comprises the steps of generating at least a first parameter based on the intrinsic event, adjusting the first therapy sequence based on the first parameter during the delivery of the therapy sequence, and / or generating at least one second therapy sequence based on the first parameter.

[0047] The inventive method enables dynamic adaptation of ATP during delivery based on the detection of an intrinsic event that indicates a tachycardia condition.

[0048] In some cases, conduction or refractoriness of the heart changes during ATP therapy. If the interpulse interval or a coupling interval between an intrinsic activity and the electrical pulse from the IMD is too short, an intrinsic excitation front may reach the pacing site between consecutive ATP pulses, which can indicate loss of pacing control and may increase a risk of tachycardia acceleration. If the interval is too long, time to entrainment increases and termination success can decrease.

[0049] According to an embodiment, an entrainment condition is detected if at least one therapy sequence succeeded in capturing the heart. For instance, the entrainment condition is detected if the detection unit detects a post-pacing interval between a last pulse of a previous therapy sequence preceding the first therapy sequence and a first detected intrinsic cardiac event after the last pulse of the previous therapy sequence, wherein the length of the post-pacing-interval exceeds an entrainment threshold, and / or if the control unit is configured to control the timing of at least one therapy sequence based on at least one propagation time. The propagation time is a time span between the delivery of at least one first electrical pulse until arrival of the first electrical pulse at a target area of the heart. The control unit is configured to determine the propagation time based on at least one signal parameter from the sensed electrical signals. Entrainment detection may additionally and / or alternatively be performed via an additional electrode pole, wherein the first electrode pole is located on a first

[0050] 24.085P-WO / / 19.03.2026electrode lead and the second electrode pole is located on a second electrode lead. In an embodiment, the control unit confirms an entrainment condition of the previous therapy sequence if a phase offset exceeds a lower threshold or is less than an upper threshold, and stores the corresponding therapy parameters of the previous therapy sequence in a memory unit for future reference.

[0051] According to an embodiment of the present invention, the detection unit detects a second tachycardia condition based on a plurality of second events in the sensed electrical signals after delivery of the first therapy sequence and determines the phase offset between the first events and the second events. In some aspects, the control unit generates the first parameter and / or a second parameter based on the phase offset.

[0052] The IMD adapts therapy in real time by measuring the phase offset created by the first therapy sequence and using that information to shape the next, e.g. the second, therapy sequence. This shortens the path to an effective ATP configuration and can reduce repeated ineffective attempts. In an embodiment, the control unit generates a second therapy sequence based on the determined phase offset only when the phase offset falls within a specified percentage range of the initial tachycardia cycle length.

[0053] Restricting adaptation to a defined phase window avoids ambiguous timing results and supports consistent decisions. According to an embodiment, a normalized offset is checked whether it lies inside an allowed range before changing therapy parameters.

[0054] In an embodiment, the percentage range used to determine the applicability of phase offset-based therapy adjustment is set between 10% and 90% of the initial TCL.

[0055] In an embodiment, the detection unit determines the phase offset between tachycardia events only when the first tachycardia cycle length, tied to the first tachycardia condition, and a second tachycardia cycle length, tied to the second tachycardia condition, are considered similar, facilitating meaningful comparison and therapy adjustment.

[0056] According to an embodiment, a similar tachycardia cycle length is confirmed if the difference between at least one interval length between two consecutive events of the first events and an interval length between two consecutive events of the second events is smaller than a threshold difference, or if the difference between a mean interval length of the first events and a mean interval length of

[0057] 24.085P-WO / / 19.03.2026the second events is smaller than a threshold difference. For example, the threshold difference is 10 ms.

[0058] In an embodiment, the similarity of tachycardia cycle lengths is defined as the difference between the first and second tachycardia cycle lengths being less than or equal to 10 milliseconds for phase offset determination.

[0059] In an embodiment, the detection unit calculates the phase offset by virtually extending the timeline of first detected events through estimated events spaced by the initial tachycardia cycle length. The offset is then computed as the temporal deviation between one estimated event and its nearest subsequent second event, normalized to the initial tachycardia cycle length. The temporal deviation is called offset time interval in the following.

[0060] In an embodiment, the detection unit computes the phase offset by measuring the interval between the last event of the first detected intrinsic cardiac events and the first event of the second detected intrinsic cardiac events, dividing this interval by the first tachycardia cycle length TCL 1 , and defining the remainder of this division as the offset time interval. The phase offset is then derived relative to the initial tachycardia cycle length.

[0061] Using the remainder of the division yields the same normalized phase regardless of how many full cycles elapse between windows. According to an embodiment, a modulo-based computation is simple and efficient for embedded processing.

[0062] According to an embodiment of the present invention, the phase offset PS is determined by an angle calculated by

[0063] PS = OTI / TCLl*2*7i

[0064] or

[0065] PS = (1-OTI / TCL1) *2*7i

[0066] whereby OTI is the offset time interval and TCL1 is the first tachycardia cycle length.

[0067] Furthermore, according to an aspect of the invention, the tachycardia cycle length is a mean or median interval length which is determined across at least 3 events of the first events or the second events.

[0068] 24.085P-WO / / 19.03.2026In an embodiment, the second therapy sequence includes the same number of electrical pulses as the first therapy sequence, plus one additional pulse. The inter-pulse intervals for the initial pulses are uniform, while the interval between the additional pulse and the last of the initial pulses is shorter if a non-zero phase offset is detected, or equal if the phase offset is zero. Adding one pulse and shortening only the terminal interval when a non-zero offset is present provides a minimal yet targeted change that increases the likelihood of effective interaction. According to an embodiment, the initial ipi is kept constant and the final interval selectively shortened when the measured phase offset indicates a therapeutic benefit.

[0069] According to an embodiment, the propagation time PT is defined as a time span between the delivery of at least one first electrical pulse and the arrival of the electrical pulse at a target area of the heart. For assessing PT, the detection unit of the implantable medical device detects events in sensed electrical signals and analyzes time intervals between the events. The detection unit extracts at least one signal parameter SP from the sensed electrical signals prior to delivering the first electrical pulse and / or during a specific operation mode. The signal parameter SP comprises at least one of a runtime between two events measured in the electrical signals, wherein a first event is measured via a first electrode pole and a second event is measured via a second electrode pole. The control unit determines a QRS width in the electrical signals, a distance between extrema in the electrical signals, and / or an area under a curve.

[0070] According to an embodiment, the control unit determines the propagation time PT based on the at least one signal parameter SP, including by generating a weighted sum comprising a plurality of weights.

[0071] Alternatively or in combination, the control unit is configured to determine a QRS width and / or an RV-LV delay that indicates a time delay between a right ventricular depolarization and a left ventricular depolarization in the sensed electrical signals. PT can be determined using the RV-LV delay and / or by PT = QRS width * x, wherein x is a correction factor for the measurement inaccuracy of QRS width.

[0072] In an example, if the detection unit detects a second tachycardia condition based on a plurality of second events after delivery of the first therapy sequence, the detection unit is configured to measure a first post-pacing interval between the last pulse of the first therapy sequence and a first detected intrinsic cardiac event following the last pulse of the first therapy sequence. The stimulation unit is further configured to deliver a second therapy sequence to the heart. If the detection unit detects a

[0073] 24.085P-WO / / 19.03.2026third tachycardia condition, based on a plurality of third events after delivery of the second therapy sequence, it is configured to measure at least one second post-pacing interval between the last pulse of the second therapy sequence and a first detected intrinsic cardiac event following the last pulse of the second therapy sequence. Moreover, the control unit is configured to compute a first relation parameter between the first post-pacing interval and the second post-pacing interval. Based on the first relation parameter, the control unit is configured to generate a third therapy sequence.

[0074] In an embodiment of the IMD according to the invention, a tachycardia condition is detected if: - The time intervals between the events have a tachycardia cycle length shorter than a tachycardia threshold, and

[0075] - The time intervals between the events fulfill at least one stability parameter.

[0076] This approach enhances detection accuracy by incorporating both timing and stability metrics, reducing false positives and ensuring appropriate initiation of therapy only during confirmed tachycardia episodes.

[0077] In an embodiment, the implantable device is configured to determine stability parameters such as a difference between a predetermined number of preceding tachycardia cycle lengths and a stability threshold value, a standard deviation, a dominant frequency derived from frequency analysis, or autocorrelation-based parameters to assess the stability consistency of tachycardia events before confirming a tachycardia condition.

[0078] According to an embodiment the tachycardia threshold is set to a value from the range of 100-250 bpm. For example, with higher tachycardia rates, multiple tachycardia thresholds can be programmed depending on the tachycardia rate, defining different tachycardia zones, as for instance:

[0079] Ventricular tachycardia (VT) zone 1 is defined as tachycardias equal to or greater than 150bpm.

[0080] VT zone 2 is defined as tachycardias equal to or greater than 187bpm.

[0081] Ventricular Fibrillation (VF) zone 3 is defined as tachycardias equal to or greater than 222bpm.

[0082] In an embodiment, the control unit generates an inter-pulse interval that is shorter than the tachycardia cycle length of preceding cardiac events. This interval is defined either between pulses

[0083] 24.085P-WO / / 19.03.2026within a therapy sequence if multiple pulses are present or between the tachycardia pulse and the first pulse of the therapy sequence if only one pulse is delivered.

[0084] Implementing inter-pulse intervals shorter than the tachycardia cycle length improves the likelihood of successfully interrupting tachycardias, thereby enhancing therapy efficacy.

[0085] According to an embodiment of the present invention, the relation parameter is a difference between two successively measured post-pacing intervals.

[0086] Using the difference between two successively measured post-pacing intervals enables precise assessment of therapy impact, facilitating optimized adjustment of therapy sequences in response to real-time measurements of cardiac activity.

[0087] In an embodiment, the control unit is configured to generate at least one therapy sequence by adjusting at least one of the following parameters:

[0088] - A duration of the therapy sequence,

[0089] - A number of pulses of a therapy sequence,

[0090] - An inter-pulse interval between at least two pulses of a therapy sequence,

[0091] - A coupling interval RSi between the last pulse of the events having a tachycardia condition and the first pulse of a therapy sequence,

[0092] - A maximum number of therapy sequences,

[0093] - A maximum duration of the therapy sequence,

[0094] - A minimum and / or maximum duration between successive therapy sequences.

[0095] For example, if atherapy sequence that includes the alternating-interval portion (group Al or Bl) is not successful, the detection unit determines a post-pacing interval immediately after the attempt and compares it to the tachycardia cycle length (TCL) measured before and / or after the attempt. If the post-pacing interval is smaller than a factor k of the TCL — preferably with k<l .0, k<l .5, or k<2.0 — the control unit is configured to adapt the parameterization by lengthening at least one of the previously shortened intervals of the alternating portion. The lengthening is performed within the permitted bounds of the interval-generation rules (e.g., using the relation L=a-T+b and selecting values of a and / or b that increase the affected interval while remaining within the ranges specified for a and b).

[0096] 24.085P-WO / / 19.03.2026According to an embodiment, the control unit is configured to determine a coupling interval between a last pulse of the first events and the first pulse of the first therapy sequence on the basis of the tachycardia cycle length. Determining a coupling interval based on tachycardia cycle length can facilitate consistent timing of therapy initiation relative to detected tachycardia behavior.

[0097] According to an aspect, the IMD is a cardiac pacemaker, an implantable cardioverter-defibrillator (ICD), a cardiac rhythm management therapy (CRT) device, or a conduction system pacing (CSP) device.

[0098] Features that are described in the context of separate aspects and embodiments of the invention may be used together and / or be interchangeable. Similarly, features described in the context of a single embodiment may also be provided separately or in any suitable subcombination.

[0099] The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:

[0100] Fig. 1 illustrates a schematic view of an implantable medical device interacting with a heart.

[0101] Fig. la shows a diagram illustrating detection of a tachycardia, delivery of an anti-tachycardia pacing therapy sequence, and the occurrence of intrinsic events during the delivery.

[0102] Fig. lb shows a schematic view of a reentry mechanism underlying a tachycardia of a heart.

[0103] Fig. 1c shows a schematic view of a fracturing of excitation fronts and development toward ventricular fibrillation after intrinsic events of a heart.

[0104] Fig. 2 shows a timing diagram illustrating cancellation of an anti -tachycardia pacing therapy sequence after detection of an intrinsic event and initiation of a subsequent therapy sequence with prolonged intervals.

[0105] Fig. 3 shows a timing diagram illustrating continuation of an anti-tachycardia pacing therapy sequence after detection of an intrinsic event, with subsequent pulses coupled to the intrinsic event and prolonged inter-pulse intervals.

[0106] 24.085P-WO / / 19.03.2026Before the present compositions, articles, devices, and / or methods are disclosed and described, it is to be understood that the aspects described below are not limited to specific methods as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

[0107] For purposes of reading the description of the various implementations below, the following descriptions of the sections of the Specification and their respective contents may be helpful:

[0108] Figure 1 shows the implantable medical device 10 connected to a heart 11 via electrode poles 111. The implantable medical device consists of a stimulation unit 12, detection unit 13, control unit 14 and memory unit 15. These components are enclosed within the implantable medical device housing for device 10. Fig. 1 shows the stimulation unit 12 delivering electrical pulses to the heart 11 through the electrode poles 111, enabling detection of cardiac events via the detection unit 13. The detection unit 13 analyzes time intervals between cardiac events to recognize tachycardia conditions and feeds this information to the control unit 14. Figure 1 shows the control unit 14 in a closed-loop configuration with the detection unit 13 and stimulation unit 12, allowing dynamic adjustment of therapy sequences based on real-time cardiac event analysis. The memory unit 15 stores parameters such as post-pacing intervals, contributing to therapy sequence adjustments. The control unit 14 might receive enhanced feedback from additional sensors or employ advanced algorithms to predict and adjust therapy sequences, optimizing therapy outcomes, and adapting to patient-specific needs. The stimulation unit may deliver at least one therapy sequence TSi, 170, i being an index number. TSi 170 can be composed of two phases, a first burst phase 171 that is characterized by a number of equidistant stimulation pulses SISI, and a ramp phase 172, that is characterized by at least one pulse with a coupling interval that decreases in length to the previous inter-pulse-interval S1S2 / S2S2.

[0109] After a therapy sequence TSi has been delivered, the detection unit may determine:

[0110] - The post pacing interval Pli between the last delivered pulse of TSi and the first sensed cardiac event thereafter,

[0111] - The difference D of post-pacing intervals for consecutively delivered therapy sequences, D = Pli - Pl(i-l); and

[0112] - The phase offset of the tachycardia before and after Pli, that may be induced or modified by the delivered therapy sequence.

[0113] 24.085P-WO / / 19.03.2026Figure la illustrates a sensed voltage at one of the electrode poles pairs against time. A tachycardia condition is identified in 100, followed by delivery of an ATP therapy sequence 110, and the occurrence of intrinsic events 120, 121 resulting from short inter-pulse intervals of the ATP therapy sequence.

[0114] In Figure lb, the tachycardia 100 is shown as a reentrant activation pattern 130 that produces recurring excitation fronts. The therapy sequence 110 is applied to interact with this reentrant activity, but when the inter-pulse intervals become too short, the intrinsic events 120, 121 arise during the sensing windows between consecutive pulses of the therapy sequence. These intrinsic events cause disruption of the excitation pattern, contributing to fracturing of wavefronts and potential deterioration of cardiac activation by the therapy sequence, as illustrated in Figure 1c.

[0115] Figure 2 illustrates a therapy sequence 110 being aborted when an intrinsic event 120 is detected during delivery. A scheduled succeeding pulse 200 of the therapy sequence and any subsequent pulses of that therapy sequence are no longer delivered. Prior to cancellation, pulses of the therapy sequence 110 are separated by an inter-pulse interval 210. After the detection of the intrinsic event 120, a new pacing sequence 110a is initiated, characterized by inter-pulse intervals 220 that are longer than the inter-pulse interval 210 that preceded the intrinsic event. These prolonged intervals 220 reduce the likelihood of repeated intrinsic events and enable a more stable interaction with the underlying reentry mechanism.

[0116] Figure 3 illustrates an alternative embodiment in which the therapy sequence 110 is not cancelled after detection of an intrinsic event 120. As in Figure 2, a scheduled succeeding pulse 200 of the therapy sequence is no longer delivered, but the timing of the succeeding pulse is adapted so that the inter-pulse interval 300 between the pulse preceding the intrinsic event and the pulse immediately following it is prolonged relative to the original inter-pulse interval 210. Further pulses of the continued sequence 110b may include additional prolonged inter-pulse intervals 310 that exceed the original inter-pulse interval 210, thus avoiding return to a destabilizing inter-pulse interval. By coupling the ongoing sequence 110b to the intrinsic event 120, the ATP therapy retains the entrainment progress already achieved while reducing the risk of inducing further destabilization.

[0117] 24.085P-WO / / 19.03.2026LIST OF REFERENCE SIGNS

[0118] 10 Implantable medical device (IMD)

[0119] 11 Heart

[0120] 111 Electrode pole(s)

[0121] 12 Stimulation unit

[0122] 13 Detection unit

[0123] 14 Control unit

[0124] 15 Memory unit

[0125] 170 Therapy sequence TSi

[0126] 171 Burst phase

[0127] 172 Ramp phase

[0128] 100 Tachycardia

[0129] 110 First anti-tachycardia pacing ATP therapy sequence

[0130] 110a Subsequent therapy sequence after cancellation

[0131] 110b Continued therapy sequence after intrinsic event

[0132] 120 Intrinsic event during ATP delivery

[0133] 121 Additional intrinsic event

[0134] 130 Reentrant activation pattern

[0135] 200 Scheduled succeeding pulse of therapy sequence

[0136] 210 Inter-pulse interval of original therapy sequence

[0137] 220 Prolonged inter-pulse interval of next therapy sequence 300 Prolonged inter-pulse interval following intrinsic event 310 Additional prolonged inter-pulse intervals in continued sequence

[0138] 24.085P-WO / / 19.03.2026

Claims

Claims1. Implantable medical device (IMD) for anti-tachycardia (100) pacing (ATP) of a heart (11), comprising:at least a first pair of electrode poles (111) configured to sense electrical signals of the heart (11) and / or to apply electrical pulses to the heart (11),a stimulation unit (12), configured to deliver the electrical pulses to the heart (11) via the first pair of electrode poles (111), wherein the stimulation unit (12) is configured to deliver at least one therapy sequence (170) to the heart (11), wherein the therapy sequence (170) comprises at least one electrical pulse, a detection unit (13), configured to detect the sensed electrical signals, to detect events in the sensed electrical signals, to analyze time intervals between the events, and to detect a tachycardia (100) condition based on the events,a control unit (14), configured to :i. generate at least one therapy sequence (170), andii. generate at least one parameter based on the events,wherein the stimulation unit (12) is configured to deliver a first therapy sequence (170) comprising at least one electrical pulse to the heart (11) if the detection unit (13) detects a first tachycardia (100) condition based on a plurality of first events, wherein the first therapy sequence (170) is delivered via the first pair of electrode poles (111), characterized in thatthe detection unit (13) is configured to detect at least one intrinsic event (120) of the heart (11) in the sensed electrical signals during the delivery of the first therapy sequence (170), wherein the intrinsic event (120) indicates that a tachycardia (100) condition is present,wherein the control unit (14) is configured to generate at least a first parameter based on the intrinsic event (120),wherein the control unit (14) is configured to adjust the first therapy sequence (170) based on the first parameter during the delivery of the therapy sequence (170), and / or generate at least one second therapy sequence (170) based on the first parameter.

2. IMD according to claim 1, wherein the detection unit (13) is configured to detect the intrinsic event (120) viathe first pair of electrode poles (111), or24.085P-WO / / 19.03.2026a second pair of electrode poles (111), wherein at least one electrode pole (111) of the second pair of electrode poles (111) is different from the electrode poles (111) of the first pair of electrode poles (111).

3. IMD according to claim 1 or 2, wherein the first parameter is at least one of the following:a duration of the first and / or second therapy sequence (170),a number of pulses of the first and / or second therapy sequence (170), an inter-pulse interval between at least two pulses of the first and / or second therapy sequence (170),a coupling interval between the intrinsic event (120) and a pulse of the first therapy sequence (170).

4. IMD according to at least one of the preceding claims, wherein the first therapy sequence (170) comprises a plurality of inter-pulse intervals, and wherein the control unit (14) is configured to adjust the first therapy sequence (170) by prolonging at least one inter-pulse interval of the first therapy sequence (170), wherein the prolonged inter-pulse interval immediately succeeds the intrinsic event (120), and wherein the prolonged inter-pulse interval is longer than the inter-pulse interval directly preceding the intrinsic event (120).

5. IMD according to at least one of the preceding claims, wherein the first therapy sequence (170) comprises a plurality of inter-pulse intervals, and wherein the control unit (14) is configured to adjust the first therapy sequence (170) by scheduling an electrical pulse that directly succeeds the intrinsic event (120) such that the inter-pulse interval between the electrical pulse that is delivered directly prior to the intrinsic event (120) and the electrical pulse that directly succeeds the intrinsic event (120) is prolonged to be longer than the interpulse interval that directly precedes the detection of the intrinsic event (120).

6. IMD according to any of the claims 4 or 5, wherein the second therapy sequence (170) comprises a plurality of inter-pulse intervals, and wherein the control unit (14) is configured to adjust the second therapy sequence ( 170) by prolonging at least one inter-pulse interval of the second therapy sequence (170), wherein the prolonged inter-pulse interval of the second therapy sequence (170) has a position in the second therapy sequence (170) which is the same position as, the same position minus one, or the same position plus one as the position of the prolonged inter-pulse interval in the first therapy sequence (170), and wherein the prolonged inter-pulse interval of the second therapy sequence (170) is longer than the inter-24.085P-WO / / 19.03.2026pulse interval of the first therapy sequence (170) which directly precedes the detection of the intrinsic event (120).

7. IMD according to at least one of the preceding claims, wherein the control unit (14) is configured to cancel the delivery of the first therapy sequence (170) if the detection unit (13) detects the intrinsic event (120).

8. IMD according to at least one of the preceding claims, wherein the control unit (14) is configured to generate the first and / or second therapy sequence (170) such that it comprises at least a succession of inter-pulse intervals having a decreasing length, wherein the control unit (14) is configured to generate no further decrease of an inter-pulse interval succeeding the detection of the intrinsic event (120).

9. IMD according to at least one of the preceding claims, wherein the control unit (14) is configured to generate at least one inter-pulse interval of the first therapy sequence (170) or second therapy sequence (170) that succeeds the detection of the intrinsic event (120) and that is of equal length or longer than the shortest inter-pulse interval that preceded the detection of the intrinsic event (120), and which did not lead to detection of the intrinsic event (120).

10. IMD according to at least one of the preceding claims, wherein the control unit (14) is configured tostore the inter-pulse interval which directly preceded the detection of the intrinsic event (120) in a memory unit (15), andadjust at least one of the first, second or a further therapy sequence (170) such that at least one inter-pulse interval of the therapy sequence (170) is longer than the stored inter-pulse interval.

11. IMD according to claim 10, wherein a group of said stored inter-pulse intervals is arranged at the beginning of at least one further therapy sequence (170).

12. IMD according to claim 10 or 11, wherein the control unit (14) is configured to store at least a first tachycardia (100) cycle length of the first tachycardia (100) condition leading to the delivery of the first therapy sequence (170), and wherein the control unit (14) is configured to generate at least one further therapy sequence (170) if a further tachycardia (100) cycle24.085P-WO / / 19.03.2026length is sufficiently similar to the first tachycardia (100) cycle length, wherein the at least one further therapy sequence (170) comprises at least a group of said stored inter-pulse intervals.

13. IMD according to at least one of the claims 3 to 12, wherein the control unit (14) is configured to adjust and / or generate a programmable number of inter-pulse intervals of the first, second and / or further therapy sequence (170) based on the first parameter.

14. IMD according to at least one of the preceding claims, wherein at least one electrode pole (111) is at least a part of a housing of the IMD, and / or wherein at least one electrode pole (111) is located to detect electrical signals from a left ventricle of the heart (11).

15. Method for operating an implantable medical device (IMD) for stimulating a human or animal heart (11), characterized by the following steps:detect a first tachycardia (100) condition based on a plurality of first events in an electrical signal of the heart (11),deliver a first therapy sequence (170) comprising at least one electrical pulse to the heart (11) via a first pair of electrode poles (111),detect at least one intrinsic event (120) of the heart (11) in the sensed electrical signals during the delivery of the first therapy sequence (170), wherein the intrinsic event (120) indicates that a tachycardia (100) condition is present, generate at least a first parameter based on the intrinsic event (120), adjust the first therapy sequence (170) based on the first parameter during the delivery of the therapy sequence (170), and / or generate at least one second therapy sequence (170) based on the first parameter.24.085P-WO / / 19.03.2026

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