Anti-tachycardia pacing implantable medical device

Abstract

An implantable medical device (IMD) for anti-tachycardia pacing (ATP) of a heart is provided. The IMD comprises at least one first electrode pole configured to sense electrical signals of the heart and to apply electrical pulses to the heart. The IMD further comprises a stimulation unit configured to deliver the electrical pulses to the heart via the electrode pole. The stimulation unit is configured to deliver at least one therapy sequence to the heart, wherein the therapy sequence comprises at least one electrical pulse. The IMD further comprises a detection unit configured to detect events in the sensed electrical signals, to analyze time intervals between the events, and to detect a tachycardia condition based on the events. The IMD further comprises a control unit configured to generate the at least one therapy sequence and to derive at least one parameter to adjust the therapy sequence based on the events. The control unit is configured to generate a first therapy sequence if the detection unit detects a first tachycardia condition based on a plurality of first events. The first therapy sequence comprises at least a group of pulses A1, wherein each pair of pulses has an inter-pulse- interval in between. Group A1 comprises at least one long inter-pulse interval that is longer than a first preceding inter-pulse-interval that directly precedes the long inter-pulse interval. A first successive inter-pulse interval follows the long inter-pulse interval, wherein the first successive inter-pulse interval is shorter than the long inter-pulse interval. The stimulation unit is configured to deliver the first therapy sequence to the heart.

Description

[0001] Anmelder: BIOTRONIK SE & Co. KG

[0002] Datum: 17.03.2026

[0003] Unser Zeichen: 24.079P-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] 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.

[0008] 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.

[0009] 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 asan 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 is provided. The IMD comprises at least one first electrode pole configured to sense electrical signals of the heart and to apply electrical pulses to the heart. The IMD further comprises a stimulation unit configured to deliver the electrical pulses to the heart via the electrode pole. The stimulation unit is configured to deliver at least one therapy sequence to the heart, wherein the therapy sequence comprises at least one electrical pulse. The IMD further comprises a detection unit configured to detect events in the sensed electrical signals, to analyze time intervals between the events, and to detect a tachycardia condition based on the events. The IMD further comprises a control unit configured to generate the at least one therapy sequence and to derive at least one parameter to adjust the therapy sequence based on the events. The control unit is configured to generate a first therapy sequence if the detection unit detects a first tachycardia condition based on a plurality of first events. The first therapy sequence comprises at least a group of pulses Al, wherein each pair of pulses has an inter-pulseinterval in between. Group Al comprises at least one long inter-pulse interval that is longer than a first preceding inter-pulse-interval that directly precedes the long inter-pulse interval. A first successive inter-pulse interval follows the long inter-pulse interval, wherein the first successive interpulse interval is shorter than the long inter-pulse interval. The stimulation unit is configured to deliver the first therapy sequence to the heart.

[0013] 24.079P-WO / / 17.03.2026The alternating behavior of inter-pulse-intervals within group Al can improve effectiveness of ATP for tachycardia termination while maintaining a structured, parameterizable therapy sequence.

[0014] In an example, group Al comprises a second preceding inter-pulse interval that precedes the first preceding inter-pulse interval. The first and the second preceding inter-pulse intervals are either of the same length, or the second preceding inter-pulse interval is longer than the first preceding interpulse interval.

[0015] The second preceding inter-pulse interval provides an additional mechanism to modulate ATP delivery to enhance the chances of tachycardia termination.

[0016] According to an embodiment of the present invention, the first therapy sequence comprises a group of pulses AO. Group Al succeeds group AO. At least a part of the inter-pulse-intervals of group AO are of the same length or decreasing in length.

[0017] Providing a preceding group AO having non-alternating inter-pulse intervals can enable a defined transition into the alternating-interval group Al and can allow the therapy sequence to be modulated to a desired preconditioning or pacing behavior.

[0018] For example, the inter-pulse-interval with position 1 in group Al is the inter-pulse-interval between the last pulse of group AO and the first pulse of group A 1. The inter-pulse-interval with position 1 in group Al is shorter than the directly preceding inter-pulse-interval. According to an embodiment, group Al has an odd number of pulses.

[0019] A shortened first transition interval into group Al, together with an odd number of pulses in group Al, can support a defined alternating pattern as start condition and may promote a targeted timing relationship between successive stimulation pulses.

[0020] According to an embodiment, the inter-pulse-interval with position 1 in group Al is the inter-pulseinterval between the last pulse of group AO and the first pulse of group Al. The inter-pulse-interval with position 1 in group Al is longer than the directly preceding inter-pulse-interval. According to an example, group Al has an even number of pulses.

[0021] 24.079P-WO / / 17.03.2026A lengthened first transition interval into group Al, together with an even number of pulses in group Al, can provide an alternative defined start condition for the alternating pattern and can facilitate selection among different delivery variants.

[0022] In an exemplary embodiment of the present invention, the control unit is configured to generate a second therapy sequence if the detection unit detects a second tachycardia condition based on a plurality of second events after delivery of the first therapy sequence. The second therapy sequence comprises at least a group of pulses Bl. Group Bl is based on group Al, but differs in that the at least one inter-pulse interval in group Bl is shorter than the corresponding inter-pulse-interval of group Al . According to an embodiment, said inter-pulse interval has a position with an even number in group B 1. Alternatively, the at least one inter-pulse interval in group B 1 is longer than or of the same length as the corresponding inter-pulse-interval of group Al. In an example, said inter-pulse interval has a position with an odd number greater 1 in group B 1. The stimulation unit is configured to deliver the second therapy sequence to the heart.

[0023] Escalating from Al to Bl by further shortening and / or further lengthening selected inter-pulse intervals can provide a controlled further ATP attempt strategy when tachycardia persists after an initial ATP attempt.

[0024] Analogous to the first therapy sequence and AO, the second therapy sequence comprises, according to an embodiment, a group of pulses BO. Group Bl succeeds group BO. The inter-pulse-intervals of group BO are all of the same length or decreasing in length. For example, the inter-pulse-interval with position 1 in group B 1 is the inter-pulse-interval between the last pulse of group BO and the first pulse of group B 1. The inter-pulse-interval with position 1 in group B 1 is shorter than the directly preceding inter-pulse-interval. Group Bl has an odd number of pulses. According to an embodiment, the inter-pulse-interval with position 1 in group Bl is the inter-pulse-interval between the last pulse of group BO and the first pulse of group Bl. The inter-pulse-interval with position 1 in group Bl is longer than the directly preceding inter-pulse-interval. Group B 1 has an even number of pulses.

[0025] According to an aspect, at least one inter-pulse interval in group Al and / or group Bl has a length L which is calculated by L = a*T. T is the length of the directly preceding inter-pulse-interval. If the inter-pulse interval is shorter than the directly preceding inter-pulse-interval, then a > 0.4, a > 0.5 or a > 0.6, and a < 1. If the inter-pulse interval is longer than or of the same length as the directly preceding inter-pulse-interval, then a < 1.6, a < 1.4 or a < 1.2, and a > 1. Using multiplicative factor "a" relative to the directly preceding inter-pulse interval can provide a bounded adaptation of inter-

[0026] 24.079P-WO / / 17.03.2026pulse-intervals in group Al or Bl, while keeping interval changes proportionate to the preceding timing.

[0027] According to an embodiment, at least one inter-pulse interval in group Al and / or group Bl has a length L which is calculated by L = T + b. T is the length of the directly preceding inter-pulseinterval. The magnitude of b is constrained such that b < 100 ms, b < 60 ms or b < 40 ms. Using additive offset "b" provides an absolute adjustment measure that can support controlled interval modifications.

[0028] Moreover, according to an aspect of the present invention, the at least one inter-pulse interval in group Al and / or group Bl has a length L which is calculated by L = a*T + b. Combining multiplicative and additive terms can provide an enhanced degree of freedom to shape series of interpulse intervals while still referencing the directly preceding interval.

[0029] Furthermore, according to an aspect, T is equal to a tachycardia cycle length associated with the current tachycardia condition, and / or wherein a and / or b are dependent on the tachycardia cycle length. Referencing tachycardia cycle length, and / or adapting parameters as a function of tachycardia cycle length, can enable therapy timing to be aligned with patient-specific and episode-specific tachycardia dynamics.

[0030] In an exemplary embodiment, the stimulation unit is configured to deliver the first therapy sequence to the heart if the detection unit detects an entrainment condition. The entrainment condition is detected if at least one preceding therapy sequence succeeded in capturing the heart. Conditioning delivery of the first therapy sequence on detected entrainment can support delivery of the alternating-interval group when capture has been achieved, which can improve therapy applicability and reduce unnecessary delivery.

[0031] Furthermore, according to an exemplary aspect of the present invention, the entrainment condition is detected

[0032] 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

[0033] if the detection unit determines that a phase offset between the first events and the second events exceeds a lower threshold or is less than an upper threshold, and / or

[0034] 24.079P-WO / / 17.03.2026if the morphology signal difference between a reference signal and an electrical signal which is sensed after delivery of an electrical pulse of a previous therapy sequence exceeds a morphological entrainment threshold (for instance, after each electrical pulse of a previous therapy sequence, an optional check of an morphological onset is performed by determining a current signal difference between a reference signal and the current signal. The current signal difference is compared to an onset threshold. Then, entrainment is evaluated by comparing a morphological distance to an entrainment threshold with possible trend evaluation and X-out- of-Y confirmation. Optionally, a trend of the history of the ATP entrainment recognition is evaluated to confirm a recognized entrainment condition), and / or

[0035] 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 electrode lead and the second electrode pole is located on a second electrode lead.

[0036] Entrainment is the process of capturing and “over-driving” a reentrant tachycardia circuit by pacing slightly faster than the tachycardia cycle length with a sufficient number of pulses. When the pacing rate is just faster than the ongoing ventricular tachycardia (VT), 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.

[0037] 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.

[0038] 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.

[0039] 24.079P-WO / / 17.03.2026The 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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 the second events is smaller than a threshold difference. For example, the threshold difference is 10 ms.

[0045] 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.

[0046] 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

[0047] 24.079P-WO / / 17.03.2026subsequent second event, normalized to the initial tachycardia cycle length. The temporal deviation is called offset time interval in the following.

[0048] 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.

[0049] 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.

[0050] According to an embodiment of the present invention, the phase offset PS is determined by an angle calculated by

[0051] PS = OTI / TCLl*2*Pi

[0052] or

[0053] PS = (1-OTI / TCL1) * 2*Pi

[0054] whereby OTI is the offset time interval.

[0055] 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.

[0056] In 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.

[0057] 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.

[0058] 24.079P-WO / / 17.03.2026For 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.

[0059] 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.

[0060] 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.

[0061] 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 third 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.

[0062] 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

[0063] - The time intervals between the events fulfill at least one stability parameter.

[0064] 24.079P-WO / / 17.03.2026This 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.

[0065] 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.

[0066] 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:

[0067] Ventricular tachycardia (VT) zone 1 is defined as tachycardias equal to or greater than 150bpm. VT zone 2 is defined as tachycardias equal to or greater than 187bpm.

[0068] Ventricular Fibrillation (VF) zone 3 is defined as tachycardias equal to or greater than 222bpm.

[0069] In some aspects of the implantable medical device, the detection unit detects events in the sensed electrical signals via one pair of electrode poles of the first and second electrode poles during and / or after delivery of the first therapy sequence. The control unit generates at least a first parameter based on the events detected during and / or after delivery of the first therapy sequence. The first parameter is associated with an effect on the heart caused by the first therapy sequence. The control unit adjusts the first therapy sequence based on the first parameter and / or generates at least one second therapy sequence based on the first parameter. 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 within 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.

[0070] Implementing inter-pulse intervals shorter than the tachycardia cycle length improves the likelihood of successfully interrupting tachycardias, thereby enhancing therapy efficacy.

[0071] According to an embodiment of the present invention, the relation parameter is a difference between two successively measured post-pacing intervals.

[0072] 24.079P-WO / / 17.03.2026Using 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.

[0073] In an embodiment, the control unit is configured to generate at least one therapy sequence by adjusting at least one of the following parameters:

[0074] - A duration of the therapy sequence,

[0075] - A number of pulses of a therapy sequence,

[0076] - An inter-pulse interval between at least two pulses of a therapy sequence,

[0077] - A coupling interval RSi between the last pulse of the events having a tachycardia condition and the first pulse of a therapy sequence,

[0078] - A maximum number of therapy sequences,

[0079] - A maximum duration of the therapy sequence,

[0080] - A minimum and / or maximum duration between successive therapy sequences.

[0081] 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 / VTCL) measured before and / or after the attempt. If the post-pacing interval is smaller than a factor k of the TCL — preferably with k<1.0, k< 1.5, 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).

[0082] According 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.

[0083] 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.

[0084] 24.079P-WO / / 17.03.2026Furthermore, a method is proposed for operating an implantable medical device (IMD) for stimulating a human or animal heart. The method comprises detecting a first tachycardia condition based on a plurality of first events in an electrical signal of the heart. The method further comprises delivering a first therapy sequence comprising at least one electrical pulse to the heart, wherein the first therapy sequence comprises at least a group of pulses Al, and wherein each pair of pulses has an inter-pulse-interval in between. Group Al comprises at least one long inter-pulse interval that is longer than a first preceding inter-pulse-interval that directly precedes the long inter-pulse interval. A first successive inter-pulse interval follows the long inter-pulse interval, wherein the first successive inter-pulse interval is shorter than the long inter-pulse interval. The method further comprises delivering the first therapy sequence to the heart. As for the corresponding device, implementation of the proposed method can improve effectiveness of ATP for tachycardia termination through an alternating behavior of inter-pulse-intervals within group Al while maintaining a structured, parameterizable therapy sequence.

[0085] In alternative or additional embodiments, the events can also be derived from impedance, pressure, pC>2 curves, or cardiac sounds, and sensing may be performed across multiple vectors formed by the electrode poles.

[0086] According to an embodiment, the present invention and embodiments thereof are applicable to therapy delivery in the atria and / or ventricles, in transvenous or non-transvenous implantable cardioverter-defibrillators (ICDs), and in both permanent or temporary de-vices offering ATP therapy options. Cardiac events may be detected via electrical signals recorded through electrode poles or alternatively via cardiac impedance, pressure curves, oxygen partial pressure, or heart sounds. Electrode poles can be assigned vector configurations for sensing and stimulation in various combinations.

[0087] Preferably, the detection unit is configured to identify cardiac events with characteristic timing points based on threshold crossings or morphological features, and tachycardia detection units analyze cardiac rhythm characteristics, such as cycle lengths, interval stability, dominant frequencies, and morphology. For instance, the control unit is configured to decide on the appropriateness of antitachycardia therapy and whether post-pacing interval measurements should be undertaken. Differences between successive post-pacing interval measurements are evaluated using adjustable thresholds to inform subsequent therapy adjustments, including modification of therapy sequence parameters, decisions on continuation of further ATP attempts, or switching to alternative therapies.

[0088] 24.079P-WO / / 17.03.2026According to an aspect of the present invention, the at least one electrode pole can be assigned to different vectors for sensing signals of the heart and applying electrical pulses to the heart. Moreover, the detection unit is for instance configured to associate events to time points in the signals of the heart via trigger thresholds and morphological landmarks such as steepest slope, extrema, curvature -conditioned extrema, inflection points, or centroids. Tachycardia identification can further make use of morphological comparisons to reference patterns.

[0089] The described device and method apply to ventricular and / or atrial tachycardias, transvenous or non -transvenous ICDs, and implants or temporary devices that provide ATP therapy options.

[0090] According to an embodiment, post-pacing intervals, relation parameters, phase offset values, tachycardia characteristics, inter-pulse intervals and series thereof, and other therapy parameters can be stored in the memory unit, read out via a programmer device, and transmitted remotely for further evaluation.

[0091] According to an aspect of the invention, assessments of the post pacing intervals, relation parameters, phase offset and the derivation of therapy parameters may alternatively or additionally be performed by an external instance such as the programmer system or a web / app-based platform, automatically or by trained clinical staff.

[0092] As an example, parameters subject to adjustment encompass the number of pulses, inter-pulse intervals, amplitude, polarity, pulse width, charge amount, and tilt, in addition to therapy sequence characteristics such as sequence count, total duration, and timing be-tween therapy sequences. Therapy sequences may differ or be repeated for confirmation measurement purposes. Time interval determination may utilize signals from identical or differing vectors or alternative physiological signals.

[0093] According to an embodiment, the control unit is configured to store successes and / or failures of parameters configurations of delivered therapy sequences in the memory unit. The control unit may further be configured to assign a ranking among the parameter configurations according to their success rate. This ranking influences the parameterization of following therapy sequences, e.g. parameter configurations that have been successful in the past are preferentially selected, if the tachycardia related circumstances are comparable. Such circumstances can for example based on the tachycardia cycle length (TCL), the number of pulses delivered prior to the alternating-interval train

[0094] 24.079P-WO / / 17.03.2026(e.g., a burst intended for entrainment), the coupling factor of the burst, and the parameters of the alternating pattern.

[0095] 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.

[0096] 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:

[0097] Fig. 1 illustrates a schematic view of an implantable medical device interacting with a heart.

[0098] Fig. 2 shows a schematic of intrinsic rhythm, tachycardia detection, and delivery of a first ATP therapy sequence.Fig. 3a) is a schematic diagram illustrating pulse intervals of a therapy sequence, including a first portion of non-alternating pulse intervals and a second portion having alternating inter-pulse intervals according to the invention.

[0099] Figs. 3b)-3e) show schematic examples of alternating-interval pulse trains with different arrangements of shortened and lengthened inter-pulse intervals.

[0100] Figs. 3f)-3i) show further schematic variants of alternating-interval pulse trains illustrating different parameterisations.

[0101] Figs. 3j) and 3k) illustrate combinations of ramp-type first portions with alternating-interval second portions.

[0102] Fig. 4a) is a schematic diagram of a therapy sequence including a second portion of an initial alternating-interval pulse train used as the basis for subsequent adaptations.

[0103] Fig. 4b) is a schematic diagram illustrating a stretched form of the alternating-interval pulse train derived from the pattern in Fig. 4a).

[0104] 24.079P-WO / / 17.03.2026Fig. 4c) is a schematic diagram illustrating a compressed form of the alternating-interval pulse train derived from the pattern in Fig. 4a).

[0105] Fig. 5 is a diagram illustrating comparative success rates of different ATP therapies as a function of heart rate, including the alternating-interval ATP disclosed herein.

[0106] Before 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 100 connected to a heart 110 via electrode poles 111. The implantable medical device consists of a stimulation unit 120, detection unit 130, control unit 140 and memory unit 150. These components are enclosed within an implantable medical device housing of the implantable medical device 100. Fig. 1 shows the stimulation unit 120 delivering electrical pulses to the heart 110 through the electrode poles 111, enabling detection of cardiac events via the detection unit 130. The detection unit 130 analyzes time intervals between cardiac events to recognize tachycardia conditions and feeds this information to the control unit 140. Fig. 1 shows the control unit 140 in a closed-loop configuration with the detection unit 130 and stimulation unit 120, allowing adjustment of therapy sequences based on cardiac event analysis. The memory unit 150 stores parameters such as post-pacing intervals, contributing to therapy sequence adjustments. The control unit 140 may receive feedback from additional sensors or employ algorithms to predict and adjust therapy sequences, optimizing therapy outcomes, and adapting to patient-specific needs.

[0109] 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.

[0110] After a therapy sequence TSi has been delivered, the detection unit may determine:

[0111] • The post-pacing interval Pli between the last delivered pulse of TSi and the first sensed cardiac event thereafter,

[0112] 24.079P-WO / / 17.03.2026• The difference D of post-pacing intervals for consecutively delivered therapy sequences, D = Pli - Pl(i-l); and

[0113] • The phase offset of the tachycardia, e.g. obtained by comparing estimated event timing from a virtual continuation at TCL to the first subsequent post-therapy event, that may be induced or modified by the delivered therapy sequence.

[0114] Figure 2 shows a time-based schematic of intrinsic rhythm, tachycardia detection, and delivery of a first therapy sequence, along with the timing quantities used for algorithmic control. A baseline healthy rhythm exhibits a cycle length CL 209. A ventricular tachycardia (VT) then occurs with a tachycardia cycle length TCL 210, which is assessed within an observation window 210b to confirm onset and stability of the arrhythmia. Upon detection of a qualifying tachycardia, the implantable medical device delivers a therapy sequence 200 (a first therapy sequence TSi), which is coupled to the last detected intrinsic event via a coupling interval RSI 220 (e.g., chosen as a fraction of the preceding TCL 210). Successive pulses within the therapy sequence are separated by an intra-therapy sequence pulse interval SISI 230 (e.g., an inter-pulse-interval chosen as a fraction of the preceding TCL 210). This phase of equidistant pulse intervals of the therapy sequence is called the burst phase. Optionally, at least one last pulse of therapy sequence 200 can be separated by an inter-pulse interval 231 that is shorter than SISI 230. This phase of at least one shorter pulse interval at the end of a therapy sequence is called the ramp phase. If the therapy attempt is not yet successful, the tachycardia persists with a tachycardia cycle length TCL 211, which is again verified within a corresponding observation window 211b.

[0115] According to embodiments of the present invention, each therapy sequence includes a burst phase with equidistant inter-pulse intervals SISI and, optionally, a so-called ramp phase in which one or more terminal inter-pulse intervals S1S2 / S2S2 are progressively shortened relative to SISI. The therapy sequence is coupled to the last intrinsic tachycardia event via a coupling interval RSI, and parameters are conveniently normalized to the tachycardia cycle length: RSI = rs TCL with scaling factor 0.5 < rs < 1, and SISI = ipi TCL with ipi as inter-pulse-interval coupling factor and wherein ipi < rs. In preferred implementations SISI is constant over the burst, while the ramp phase shortens the terminal intervals according to a programmed S2 ramp factor. The counts NS1 (burst) and NS2 (ramp), along with RSI, SISI, and the ramp factor, provide principal degrees of freedom for dynamically adapting therapy from attempt to attempt. According to an embodiment, the ramp factor is a percentage value, wherein the length of the inter-pulse interval from the preceding pulse to the S2 pulse is defined by the preceding inter-pulse interval times the ramp factor.

[0116] 24.079P-WO / / 17.03.2026In the following Figure descriptions for Figures 3a-k and 4a-c, the term "interval" will be used instead of "inter-pulse interval" for simplicity.

[0117] Figure 3a, the intervals 300 are plotted against the pulse count 310, and the pulse train is divided into a first portion 171 and a second portion 172. The first portion 171 consists of equal or monotonically decreasing intervals consistent with a burst- or ramp-type pattern used for preparatory pacing, whereas the second portion 172 implements the alternating inter-pulse interval concept of the invention. Within the alternating portion 172, shortened intervals are indicated by downward arrows 320 and lengthened or unchanged intervals are indicated by upward arrows 330 or equal-length indications 331, thereby realising alternating shortened and lengthened intervals.

[0118] Figure 3b shows a pulse train that begins with the non-alternating first portion 171, in which the intervals are equal or decreasing, followed by an alternating-interval pulse train whose terminal portion 172 shows intervals decreasing in length, containing two successive intervals of an equal length.

[0119] In Figure 3c, the pulse train begins with the non-alternating first portion 171, in which the intervals are equal or decreasing, and transitions into the alternating portion 172. The second portion 172 exhibits alternating shortened intervals and lengthened intervals, with the shortened intervals becoming progressively shorter toward the end of the sequence to yield a more aggressive terminal pattern.

[0120] Figure 3d illustrates an alternating-interval pattern corresponding to that of Figure 3c, with the difference that the second interval, that is the long interval of alternating portion 172, is longer than the corresponding interval of the pattern in Figure 3c.

[0121] Figure 3e shows an alternating-interval pattern corresponding to that of Figure 3d, with the difference that the second interval, that is the long interval of alternating portion 172, is longer than the corresponding interval of the pattern in Figure 3d.

[0122] In Figure 3f, a non-alternating portion 171 with intervals having equal lengths precedes the alternating portion 172. The alternating pattern, comprising alternating shortened intervals and lengthened intervals, is thus appended after a burst-type sequence that may be used to achieve entrainment prior to application of alternating intervals.

[0123] 24.079P-WO / / 17.03.2026Figure 3g shows an alternating-interval pattern corresponding to that of Figure 3f, with the difference that the third interval, that is the interval that follows the long interval of alternating portion 172, is longer than the corresponding interval of the pattern in Figure 3f.

[0124] In Figure 3h, multiple alternating shortened and lengthened intervals appear in succession, with a tendency of decreasing lengths to yield a more aggressive terminal pattern. See the second and the fourth interval of portion 172, that represent the lengthened intervals compared to their preceding interval, but where the fourth interval is shorter than the second interval; and see the first, the third and the fifth interval, that represent the shortened intervals compared to their preceding interval, but where the fifth interval is shorter than the third interval, that is again shorter than the first interval.

[0125] Figure 3i shows multiple alternating shortened and lengthened intervals in succession, with a tendency of decreasing lengths for the shortened intervals and a tendency of increasing lengths for the lengthened intervals to yield a more aggressive, yet flexible terminal pattern. See the second and the fourth interval of portion 172, that represent the lengthened intervals compared to their preceding interval, but where the fourth interval is longer than the second interval; and see the first, the third and the fifth interval, that represent the shortened intervals compared to their preceding interval, but where the fifth interval is shorter than the third interval, that is again shorter than the first interval.

[0126] Figure 3j combines a ramp-type first portion 171, in which inter-pulse intervals progressively decrease, with a subsequent alternating portion 172. In the alternating portion, shortened intervals alternate with lengthened intervals, wherein the second interval of 172 is longer than its preceding interval.

[0127] Figure 3k shows a first portion 171 that comprises a burst part followed by a ramp part, in which inter-pulse intervals progressively decrease, with a subsequent alternating portion 172. In the alternating portion, shortened intervals alternate with lengthened intervals, wherein the second interval of 172 is longer than its preceding interval.

[0128] Figure 4a shows a first portion 171 that exhibits non-alternating intervals, while the second portion 172 contains alternating shortened intervals and lengthened intervals. This baseline pattern serves as the reference configuration for Figures 4b and 4c.

[0129] Figure 4b depicts a stretched pattern 400 derived from the 172 of Figure 4a. The alternating portion 400 is lengthened through selection of the parameters a and b such that each modified interval is

[0130] 24.079P-WO / / 17.03.2026longer than in 172 of Figure 4a. Figure 4c illustrates a compressed pattern 400 in which the alternating portion 400 is shortened compared to 172 of Figure 4a by applying parameter values a less than one and / or negative values of b within the permitted limits.

[0131] Figure 5 illustrates the success rate of various ATP strategies across a range of heart rates. A curve representing a conventional burst ATP approach 500 shows relatively low success across heart rates. A commercially available adaptive ATP approach 510 achieves improved success. A further adaptive solution 520 provides additional improvement. The curve 530 represents the alternating -interval ATP disclosed herein and shows the highest success rate across the heart- rate range.

[0132] 24.079P-WO / / 17.03.2026REFERENCE NUMERAL LIST

[0133] 100 implantable medical device (IMD)

[0134] 110 heart

[0135] 111 electrode pole

[0136] 120 stimulation unit

[0137] 130 detection unit

[0138] 140 control unit

[0139] 150 memory unit

[0140] 170 therapy sequence

[0141] 171 first portion

[0142] 172 second portion

[0143] 200 therapy sequence

[0144] 209 cycle length (healthy rhythm)

[0145] 210 tachycardia cycle length (TCL)

[0146] 210b observation window

[0147] 211 tachycardia cycle length after an ATP attempt 211b observation window

[0148] 220 coupling interval RS 1

[0149] 230 inter-pulse-interval SISI

[0150] 231 shortened terminal inter-pulse interval

[0151] 300 inter-pulse intervals

[0152] 310 pulse count

[0153] 320 shortening indication

[0154] 330 lengthening indication

[0155] 331 equal-length indication

[0156] 400 stretched or compressed pattern

[0157] 500, 510, 520,530 therapy success curves

[0158] 24.079P-WO / / 17.03.2026

Claims

Claims1. Implantable medical device (IMD, 100) for anti -tachycardia pacing (ATP) of a heart (110), comprising:- at least one first electrode pole (111) configured to sense electrical signals of the heart (110) and apply electrical pulses to the heart (110),- a stimulation unit (120), configured to deliver the electrical pulses to the heart (110) via the electrode pole (111), wherein the stimulation unit (120) is configured to deliver at least one therapy sequence (170) to the heart (110), the therapy sequence (170) comprising at least one electrical pulse,- a detection unit (130), configured to detect events in the sensed electrical signals, to analyze time intervals between the events, and to detect a tachycardia condition based on the events,- A control unit (140), configured to generate the at least one therapy sequence (170) and to derive at least one parameter to adjust the therapy sequence (170) based on the events,wherein the control unit (140) is configured to generate a first therapy sequence (170) if the detection unit (130) detects a first tachycardia condition based on a plurality of first events,characterized in thatthe first therapy sequence (170) comprises at least a group of pulses Al, each pair of pulses having an inter-pulse-interval in between,wherein group Al comprises at least one long inter-pulse interval that is longer than a first preceding inter-pulse-interval that directly precedes the long inter-pulse interval, and wherein a first successive inter-pulse interval follows the long inter-pulse interval, wherein the first successive inter-pulse interval is shorter than the long inter-pulse interval,wherein the stimulation unit (120) is configured to deliver the first therapy sequence (170) to the heart (110).

2. IMD ( 100) according to claim 1 , wherein group A 1 comprises a second preceding inter-pulse interval that precedes the first preceding inter-pulse interval, wherein the first and the second preceding inter-pulse intervals are of the same length, or wherein the second preceding interpulse interval is longer than the first preceding inter-pulse interval.24.079P-WO / / 17.03.20263. IMD (100) according to claim 1 or 2, wherein the first therapy sequence (170) comprises a group of pulses A0, wherein group Al is succeeding group A0, and wherein at least a part of the inter-pulse-intervals of group A0 are of the same length or decreasing in length.

4. IMD (100) according to claim 3, wherein the inter-pulse-interval with position 1 in group Al, which is the inter-pulse-interval between the last pulse of group A0 and the first pulse of group Al, is shorter than the directly preceding inter-pulse-interval.

5. IMD (100) according to claim 3, wherein the inter-pulse-interval with position 1 in group Al, which is the inter-pulse-interval between the last pulse of group A0 and the first pulse of group Al, is longer than the directly preceding inter-pulse-interval.

6. IMD (100) according to at least one of the preceding claims, wherein, if the detection unit (130) detects a second tachycardia condition based on a plurality of second events after delivery of the first therapy sequence (170), the control unit (140) is configured to generate a second therapy sequence (170), wherein the second therapy sequence (170) comprises at least a group of pulses Bl, wherein B 1 is based on Al, but differs in that:the at least one inter-pulse interval in the group B 1 is shorter than the corresponding interpulse-interval of Al,orthe at least one inter-pulse interval in the group B 1 is longer than the corresponding interpulse-interval of Al,wherein the stimulation unit ( 120) is configured to deliver the second therapy sequence (170) to the heart (110).

7. IMD (100) according to at least one of the preceding claims, wherein at least one inter-pulse interval in group A 1 and / or B 1 has a length L which is calculated byL = a*Twhereby T is the length of the directly preceding inter-pulse-interval, anda > 0.4, a > 0.5 or a > 0.6 and a < 1 if the inter-pulse interval is shorter than the directly preceding inter-pulse-interval,ora < 1.6, a < 1.4 ora < 1.2 and a > 1 if the inter-pulse interval is longer than or of the same length as the directly preceding inter-pulse-interval.24.079P-WO / / 17.03.20268. IMD (100) according to at least one of the preceding claims, wherein at least one inter-pulse interval in group A 1 and / or B 1 has a length L which is calculated byL = T+bwhereby T is the length of the directly preceding inter-pulse-interval, andb < 100ms, b < 60ms or b < 40ms.

9. IMD (100) according to claims 7 and 8, wherein the at least one inter-pulse interval in group Al and / or Bl has a length L which is calculated byL = a*T+b10. IMD (100) according to at least one of the claims 1 to 6, wherein at least one inter-pulse interval in group A 1 and / or B 1 has a length L which is calculated byL = a*T+bwherein T is equal to a tachycardia cycle length associated with the current tachycardia condition, and / ora and / or b are dependent on the tachycardia cycle length.

11. IMD (100) according to at least one of the preceding claims, wherein the stimulation unit (120) is configured to deliver the first therapy sequence (170) to the heart (110) if the detection unit (130) detects an entrainment condition, whereby an entrainment condition is detected if at least one preceding therapy sequence(170) succeeded in capturing the heart (HO).

12. IMD (100) according to claim 11, wherein the entrainment condition is detected- If the detection unit (130) detects a post-pacing interval between a last pulse of a previous therapy sequence (170) preceding the first therapy sequence (170), and a first detected intrinsic cardiac event after the last pulse of the previous therapy sequence (170), wherein the length of the post-pacing -interval exceeds an entrainment threshold, and / or- if the detection unit determines that a phase offset between the first events and the second events exceeds a lower threshold or is less than an upper threshold, and / or - if the morphology signal difference between a reference signal and an electrical signal which is sensed after delivery of an electrical pulse of a previous therapy sequence (170) exceeds a morphological entrainment threshold,- if the control unit (140) is configured to control the timing of at least one therapy sequence (170) based on at least one propagation time, the propagation time being a24.079P-WO / / 17.03.2026time 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 (110), and wherein the control unit (140) is configured to determine the propagation time based on at least one signal parameter from the sensed electrical signals,and / or- via an additional electrode pole (111), wherein the first electrode pole (111) is located on a first electrode lead, and the second electrode pole (111) is located on a second electrode lead.

13. IMD (100) according to at least one of the preceding claims, wherein the control unit (140) is configured to determine a coupling interval between a last pulse of the first events and the first pulse of the first therapy sequence (170) on the basis of the tachycardia cycle length.

14. IMD (100) according to at least one of the preceding claims, wherein the IMD (100) is a cardiac pacemaker, an implantable cardioverter-defibrillator (ICD), a cardiac rhythm management therapy (CRT) device, or a conduction system pacing (CSP) device.

15. Method for operating an implantable medical device (IMD (100)) for stimulating a human or animal heart (110), characterized by the following steps:- detect a first tachycardia condition based on a plurality of first events in an electrical signal of the heart (110),- deliver a first therapy sequence (170) comprising at least one electrical pulse to the heart (110), wherein the first therapy sequence (170) comprises at least a group of pulses Al, each pair of pulses having an inter-pulse-interval in between, wherein group Al comprises at least one long inter-pulse interval that is longer than a first preceding inter-pulse-interval that directly precedes the long inter-pulse interval, and wherein a first successive inter-pulse interval follows the long inter-pulse interval, wherein the first successive inter-pulse interval is shorter than the long inter-pulse interval,- deliver the first therapy sequence ( 170) to the heart (110).24.079P-WO / / 17.03.2026

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