Anti-tachycardia pacing implantable medical device

Abstract

An implantable medical device for anti-tachycardia pacing of a heart is proposed, comprising at least one electrode pole, a stimulation unit, a detection unit, and a control unit. The stimulation unit delivers a first therapy sequence TS1. If the detection unit detects a second tachycardia condition, a first post-pacing interval PI1 between the last pulse of TS1 and a first detected intrinsic cardiac event following the last pulse of TS1 is measured. The stimulation unit delivers a second therapy sequence TS2. If the detection unit detects a third tachycardia condition, at least one second post-pacing interval PI2 between the last pulse of TS2 and a first detected intrinsic cardiac event following the last pulse of TS2 is measured. The control unit computes a first relation parameter RP1. The detection unit is configured to detect at least one phase offset between the first events and the second events, and / or between the second events and the third events. The control unit is configured to generate a third therapy sequence TS3 depending on RP2, and / or to generate TS2 and / or TS3 based on the phase offset.

Description

[0001] Anmelder: BIOTRONIK SE & Co. KG

[0002] Datum: 20.03.2026

[0003] Unser Zeichen: 23.167P-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 as an atrial tachyarrhythmia being greater than or equal to a first detection threshold. The processor isconfigured 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 — such as intervals between delivered pulses and subsequent intrinsic ventricular events — after an initial ATP attempt to optimize the configuration of subsequent 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] This application addresses the problem of dynamically and efficiently adjusting anti-tachycardia pacing therapy sequences based on measured intrinsic cardiac events to improve therapy effectiveness and avoid ineffective repeated pulse sequences.

[0012] The formulated problem is solved by the presented device and method according to independent claims 1 and 15, and by embodiments described in the dependent claims and the accompanying figure description.

[0013] According to the invention, an implantable medical device (IMD) for anti-tachycardia pacing (ATP) of a heart is proposed, comprising:

[0014] - At least one electrode pole, configured to sense electrical signals of the heart and apply electrical pulses to the heart.

[0015] - A stimulation unit, configured to deliver electrical pulses to the heart via the electrode pole. The stimulation unit is further configured to deliver at least one therapy sequence TSi to the heart, where i is an index number, and each therapy sequence comprises at least one electrical pulse.

[0016] - A detection unit, configured to:

[0017] - detect events in the sensed electrical signals,

[0018] - analyze time intervals between the events, and

[0019] - detect a tachycardia condition based on the events.

[0020] - A control unit, configured to:

[0021] i. Generate at least one therapy sequence TSi.

[0022] ii. Derive at least one parameter to adjust the therapy sequence TSi based on the detected events.

[0023] 23.167P-WO / / 20.03.2026The stimulation unit is configured to deliver a first therapy sequence TS1, 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.

[0024] If the detection unit detects a second tachycardia condition, based on a plurality of second events after delivery of the first therapy sequence TS 1 , it is configured to measure a first post-pacing interval PI1 between the last pulse of TS1 and a first detected intrinsic cardiac event following the last pulse ofTSl.

[0025] The stimulation unit is further configured to deliver a second therapy sequence TS2 to the heart.

[0026] If the detection unit detects a third tachycardia condition, based on a plurality of third events after delivery of TS2, it is configured to measure at least one second post-pacing interval PI2 between the last pulse of TS2 and a first detected intrinsic cardiac event following the last pulse of TS2.

[0027] The control unit is configured to compute a first relation parameter RP1 between PI1 and PI2.

[0028] The detection unit is configured to detect at least one phase offset between the first events and the second events, and / or between the second events and the third events.

[0029] The control unit is configured to generate a third therapy sequence TS3 depending on the first relation parameter RP1, and / or to generate the second therapy sequence TS2 and / or the third therapy sequence TS3 based on the phase offset.

[0030] 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 (TCL) shorter than a tachycardia threshold, and

[0031] - The time intervals between the events fulfill at least one stability parameter.

[0032] 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.

[0033] 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:

[0034] Ventricular tachycardia (VT) zone 1 is defined as tachycardias equal to or greater than 150 bpm.

[0035] 23.167P-WO / / 20.03.2026VT zone 2 is defined as tachycardias equal to or greater than 187 bpm.

[0036] VF zone 3 is defined as tachycardias equal to or greater than 222 bpm.

[0037] In an embodiment, the IMD 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.

[0038] 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.

[0039] Implementing inter-pulse intervals shorter than the tachycardia cycle length improves the likelihood of successfully interrupting tachycardias, thereby enhancing therapy efficacy.

[0040] According to an embodiment of the present invention, the relation parameter is a difference D between two successively measured post-pacing intervals Pli.

[0041] 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.

[0042] In an embodiment, the detection unit determines the phase offset between tachycardia events only when the first and second tachycardia cycle lengths have a similar length.

[0043] A similar length is confirmed if a difference of an interval length of the time intervals of the first events and the interval length of the time intervals 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.

[0044] 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 TCL. The offset is then computed as the temporal deviation between one estimated event and its nearest subsequent second

[0045] 23.167P-WO / / 20.03.2026event, normalized to the initial tachycardia cycle length. The temporal deviation is called offset time interval in the following.

[0046] Virtual continuation provides a normalized phase measure even when intermediate events are missing.

[0047] 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 first tachycardia cycle length.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.

[0048] According to an embodiment of the present invention, the phase offset PS is determined by an angle calculated by

[0049] PS = OTI / TCL1 * 2*Pi

[0050] or

[0051] PS = ((l-OTI)ZTCLl) * 2*Pi

[0052] whereby OTI is the offset time interval.

[0053] Furthermore, according to an aspect of the invention, the TCL is a mean or median interval length which is determined across at least 3 events of the first events or the second events.

[0054] In an embodiment, the control unit is configured to generate at least one therapy sequence TSi by adjusting at least one of the following parameters:

[0055] - A duration of the therapy sequence,

[0056] - A number of pulses of a therapy sequence,

[0057] - An inter-pulse interval between at least two pulses of a therapy sequence,

[0058] A coupling interval RSi between the last pulse of the events having a tachycardia condition and the first pulse of a therapy sequence,

[0059] - A maximum number of therapy sequences,

[0060] - A maximum duration of the therapy sequence,

[0061] - A minimum and / or maximum duration between successive therapy sequences.

[0062] According to an embodiment of the present invention,

[0063] 23.167P-WO / / 20.03.2026- The number of therapy sequences is 10, 20, 30 or 40,

[0064] - The duration of a therapy sequence ranges between 60s to 3600s.

[0065] - The minimum duration between successive therapy sequences is 0.6s.

[0066] According to an aspect of the invention, the control unit is configured to generate at least one therapy sequence TSi by adjusting at least one of the following parameters:

[0067] - a maximum number of therapy sequences,

[0068] - a maximum duration of the therapy sequence,

[0069] - a minimum and / or maximum duration between therapy sequences.

[0070] In an example, a maximum number of therapy sequences is 40. In that example, a maximum of 2x10 sequences are delivered for a VT zone, 2x10 therapy sequences are delivered for a VF zone.

[0071] According to an embodiment, a maximum duration of the therapy sequence is 3600s.

[0072] Moreover, according to an aspect, the minimum duration is 600ms.

[0073] Adjustment of at least one parameter from a selection of multiple parameters allows customization of therapy delivery and provides flexibility to tailor anti-tachycardia pacing to individual patient cardiac dynamics.

[0074] In an embodiment of the invention,

[0075] - the coupling interval RSi is computed by rs*TCL, whereby 0.5 < rs < 1;

[0076] - the inter-pulse-interval IPIi is computed by ipi*TCL, whereby ipi < rs,

[0077] - whereby all inter-pulse-intervals of a therapy sequence are of equal length.

[0078] These timing regimes ensure that therapy delivery is adjusted according to the intrinsic cardiac cycle, and according to systematical dynamic adaptation of the anti-tachycardia pacing in successive attempts, with the target to enhance the effectiveness of anti -tachycardia pacing.

[0079] According to an embodiment of the present invention, the at least one therapy sequence TSi comprises a number of pulses Ni having a first inter-pulse-interval IPIi, that is followed by at least one further pulse S2. An inter-pulse-interval IPIis2 between the last pulse of the at least one Ni pulses and the at least one further pulse S2 is shorter than IPIi. In other words, the further pulse S2is coupled to the last pulse of the Ni pulses by inter-pulse-interval IPIs2, that is shorter than IPIi. The control unit is configured to determine IPIis2 on the basis of the difference D and / or on the basis of the phase offset.

[0080] 23.167P-WO / / 20.03.2026In an embodiment of the invention, the at least one therapy sequence TSi comprises a plurality of further pulses S2...Sn, wherein the inter-pulse-intervals IPIis2... IPIisn decrease in length. The control unit is configured to determine the lengths of the inter-pulse-intervals IPIis2... IPIisn on the basis of the difference D and / or on the basis of the phase offset.

[0081] For instance, the control unit is configured to determine the decrease in lengths by successively shortening each inter-pulse-interval IPIis2... IPIisn by a pre-determined time period or by a percentage value PV in relation to the preceding inter-pulse interval.

[0082] Said phase of at least one shorter pulse interval at the end of a therapy sequence is called the ramp phase. According to embodiments of the present invention, each therapy sequence includes a burst phase with equidistant inter-pulse intervals IPIi and, optionally, a so-called ramp phase in which one or more terminal inter-pulse intervals IPIis2 are progressively shortened relative to IPIi. In an exemplary embodiment, IPIi is constant over the burst phase, while the ramp phase shortens the terminal intervals according to a programmed S2 ramp factor. The counts NS1 (burst) and NS2 (ramp), along with IPIi, and the ramp factor, provide degrees of freedom for dynamically adapting therapy from attempt to attempt. According to an embodiment, the ramp factor refers to the percentage value PV, 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.

[0083] Furthermore, according to an embodiment of the present invention, the at least one therapy sequence TSi comprises a number of pulses Ni, wherein the control unit is configured to determine Ni on the basis of the phase offset and / or on the basis of the difference D.

[0084] Additionally or alternatively, the at least one therapy sequence TSi comprises a number of pulses of a ramp phase N S2i, wherein the control unit is configured to determine NS2i on the basis of the phase offset and / or on the basis of the difference D.

[0085] According to an exemplary embodiment of the present invention, the control unit is configured to store in a memory unit the smallest number of pulses Ns of a therapy sequence TSs out of a number of therapy sequences n, wherein Ns leads to a longest post-pacing interval Pls between the last pulse of the therapy sequence TSs and a first detected intrinsic cardiac event after the last pulse of the therapy sequence out of a number n of post-pacing intervals.

[0086] 23.167P-WO / / 20.03.2026Retaining the minimal effective pulse count that maximizes post-pacing interval allows the device to optimize therapy efficiency, reducing unnecessary stimulation while maintaining efficacy.

[0087] According to an embodiment, Ns is the number of SI pulses required for the therapy sequence to take control over the reentry — known in the scientific literature as entrainment.

[0088] If entrainment is detected, this fact is reported along with the corresponding therapy sequence parameters, for example:

[0089] - to the control unit, which takes this into account when configuring subsequent therapy sequences, - made available to external entities,

[0090] - stored for later processing or retrieval.

[0091] In particular, the value Ns is made available for further processing.

[0092] In an embodiment, the control unit confirms a positive therapeutic effect of the first therapy sequence if the phase offset exceeds a lower threshold or is less than an upper threshold, and stores the corresponding therapy parameters in memory for future reference.

[0093] This positive therapeutic effect is also referring to the entrainment state. A threshold-based confirmation avoids uncertain results and preserves successful parameter sets for future use. According to an embodiment, confirmed configurations are written to memory for later retrieval and reuse in similar tachycardia conditions.

[0094] According to a further aspect of the present invention, a method for operating an IMD for stimulating a human or animal heart is proposed, characterized by the following steps:

[0095] - Detect a first tachycardia condition based on a plurality of first events in an electrical signal of the heart.

[0096] - Deliver a first therapy sequence TS1, comprising at least one electrical pulse to the heart.

[0097] - If a second tachycardia condition is detected, based on a plurality of second events after delivery of the first therapy sequence TS1, measure a first post-pacing interval PI1 between the last pulse of the first therapy sequence TS 1 and a first detected intrinsic cardiac event after the last pulse of TS 1. - Deliver a second therapy sequence TS2 to the heart.

[0098] - If a third tachycardia condition is detected, based on a plurality of third events after delivery of the second therapy sequence TS2, measure a second post-pacing interval PI2 between the last pulse of the second therapy sequence TS2 and a first detected intrinsic cardiac event after the last pulse of TS2.

[0099] 23.167P-WO / / 20.03.2026- Compute a first relation parameter RP1 between PI1 and PI2.

[0100] - Detect at least one phase offset between the first events and the second events, and / or between the second events and the third events.

[0101] - Generate a third therapy sequence TS3 depending on the first relation parameter RP 1.

[0102] - Generate the second therapy sequence TS2 and / or the third therapy sequence TS3 based on the phase offset.

[0103] This method enables closed-loop adaptive anti -tachycardia therapy, where real-time feedback is used for adjusting pacing sequences, improving the specificity and effectiveness of anti-tachycardia therapy.

[0104] According to an embodiment of the inventive method, the relation parameter is a difference D between two successively measured post-pacing intervals Pli.

[0105] In other words, the relation parameter used for adjusting therapy is defined as the difference between two successively measured post-pacing intervals.

[0106] 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

[0107] According 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.

[0108] 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.

[0109] 23.167P-WO / / 20.03.2026The 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.

[0110] According to an embodiment, post pacing intervals, relation parameters, phase offset values, tachycardia characteristics, and therapy parameters can be stored in the memory unit, read out via a programmer device, and transmitted remotely for further evaluation.

[0111] According to an embodiment of the present invention, 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.

[0112] 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 web / app-based platform, automatically or by trained clinical staff.

[0113] 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.

[0114] DEFINITIONS

[0115] The term „IMD" as used herein refers to an implantable medical device configured for sensing cardiac electrical signals and delivering electrical pulses to the heart for ATP therapy.

[0116] The term „electrode pole" as used herein refers to a component of the implantable medical device designed to both sense electrical signals from the heart and deliver electrical pulses to the heart tissue.

[0117] The term „electrical pulses" as used herein refers to programmed electrical stimuli delivered via electrode poles to the heart to modify cardiac rhythm during ATP therapy.

[0118] The term „heart" as used herein refers to the human or animal cardiac organ whose electrical activity is monitored and therapeutically influenced by the implantable medical device.

[0119] The term „electrical pulse" as used herein refers to a single therapeutic electrical pulse delivered to the heart as part of a therapy sequence.

[0120] 23.167P-WO / / 20.03.2026The term „post-pacing interval" as used herein refers to a time interval measured from the last delivered electrical pulse of a therapy sequence to the first subsequent intrinsic cardiac event.

[0121] The term difference D" as used herein refers to the calculated difference between two consecutively measured post-pacing intervals used as a relation parameter for adjusting therapy.

[0122] The term „events" as used herein refers to distinct cardiac electrical occurrences detected in sensed signals, including intrinsic cardiac actions and delivered pulses.

[0123] The term ..stimulation unit" as used herein refers to the component of the implantable medical device that delivers programmed electrical pulses to the heart via electrode poles.

[0124] The term „Implantable medical device" as used herein refers to a device implanted in the body that monitors cardiac electrical signals and provides electrical pacing therapy to treat tachycardia.

[0125] The term „first tachycardia condition" as used herein refers to an initial detection of a tachycardia state identified by analyzing cardiac events and intervals which triggers delivery of a first therapy sequence.

[0126] The term „time intervals" as used herein refers to measured durations between detected cardiac electrical events used to assess cardiac rhythm conditions.

[0127] The term "estimated events in succession" as used herein refers to computed event timings created by extending the timeline of detected events spaced by the TCL to facilitate phase offset calculation.

[0128] The term „electrical signal" as used herein refers to the cardiac electrical activity recorded by the implantable medical device's sensing electrodes.

[0129] The term „second therapy sequence TS2" as used herein refers to the subsequent therapy sequence delivered after the first, in response to persistent tachycardia, consisting of one or more electrical pulses.

[0130] The term „memory unit" as used herein refers to the storage component of the implantable medical device that retains therapy parameters and measurement data such as pulse counts and post-pacing intervals.

[0131] 23.167P-WO / / 20.03.2026The term „cardiac pacemaker" as used herein refers to a type of implantable medical device that provides electrical pacing to regulate the heart rhythm.

[0132] The term "remainder" as used herein refers to the fractional part left over when dividing the interval between detected events by the TCL, used to derive the phase offset.

[0133] The term „control unit" as used herein refers to the implantable medical device component responsible for analyzing detected cardiac events, computing parameters, and adjusting therapy sequences dynamically.

[0134] The term „ICD" as used herein refers to an implantable cardioverter-defibrillator device capable of delivering ATP and high-energy shocks to treat arrhythmias.

[0135] The term "dominant frequency" as used herein refers to the main frequency component derived from frequency analysis of detected cardiac events, indicative of rhythm regularity in tachycardia.

[0136] The term „coupling interval RSi" as used herein refers to the time interval between the last intrinsic tachycardia event and the first pulse of a therapy sequence, typically expressed as a fraction of the TCL. “i” is an index number.

[0137] The term „first relation parameter" as used herein refers to a computed value derived from comparing two post-pacing intervals that guides adjustment of subsequent therapy sequences.

[0138] The term „therapy sequence TSi" as used herein refers to a series of one or more electrical pulses delivered to the heart as a coordinated therapeutic intervention indexed by i.

[0139] The term „therapy sequence" as used herein refers generally to a group of electrical pulses delivered in succession to interrupt tachycardia.

[0140] The term „electrical signals" as used herein refers to the cardiac electrical activity continuously sensed by the implantable medical device for rhythm analysis.

[0141] The term „inter-pulse interval IPIi" as used herein refers to the time interval between consecutive pulses within a therapy sequence or between the tachycardia pulse and the first pulse of a singlepulse therapy sequence. “I” is an index number.

[0142] 23.167P-WO / / 20.03.2026The term „PI2" as used herein refers synonymously to the second post-pacing interval measured after the second therapy sequence.

[0143] The term „ATP" as used herein refers to anti -tachycardia pacing, a therapy involving electrical pulses to terminate tachycardia by interrupting abnormal cardiac rhythms.

[0144] The term ..parameter" as used herein refers to a quantifiable characteristic or variable used by the control unit to configure or adjust therapy sequences.

[0145] The term „detection unit" as used herein refers to the implantable medical device component responsible for sensing cardiac electrical events and analyzing them to identify tachycardia conditions.

[0146] The term „anti-tachycardia pacing" as used herein refers to a therapeutic technique using controlled electrical pulses to halt tachycardia by resetting the pathological cardiac electrical circuit.

[0147] The term „sensed electrical signals" as used herein refers to the electrical cardiac signals recorded by the implantable medical device's electrode poles for rhythm detection.

[0148] The term „first events" as used herein refers to the plurality of cardiac electrical events detected prior to and triggering the first therapy sequence.

[0149] The term „tachycardia condition" as used herein refers to a state of abnormally fast cardiac rhythm identified by analyzing intervals and characteristics of detected cardiac events.

[0150] The term „first detected intrinsic cardiac event" as used herein refers to the earliest intrinsic (natural) cardiac electrical occurrence detected following the last pulse of a therapy sequence.

[0151] The term ..conduction system pacing (CSP) device" as used herein refers to a cardiac pacing system designed to deliver electrical stimulation directly to the heart’s intrinsic conduction system — primarily the His bundle or the left bundle branch area — rather than to the right ventricular myocardium.

[0152] The term "stability parameter" as used herein refers to a quantitative measure for evaluating the consistency and regularity of tachycardia events for accurate detection.

[0153] 23.167P-WO / / 20.03.2026The term „ cardiac rhythm management therapy (CRT) device " as used herein refers to an implantable pacemaker — sometimes combined with a defibrillator (CRT-P / CRT-D) — that delivers coordinated pacing to both ventricles (and often the right atrium) to resynchronize heart contractions in selected heart-failure patients with electrical conduction delays, improving pump efficiency and symptoms.

[0154] The term „therapy module" as used herein refers to a type of therapeutic measure of a cardiac pacing system designed to deliver electrical stimulation.

[0155] Fig. 1 illustrates a schematic view of an implantable medical device interacting with a heart.

[0156] Fig. 2 shows a schematic of intrinsic rhythm, tachycardia detection, and delivery of a first ATP therapy sequence

[0157] Fig. 3 shows an exemplary therapy sequence delivered during a tachycardia episode according to embodiments of the invention.

[0158] Fig. 4 illustrates an embodiment for determining the stability measure TCLs by the detection unit at the time the stability check is executed.

[0159] Fig. 5a illustrates an exemplary succession of therapy sequences delivered along a continuous time axis during one tachycardia episode.

[0160] Fig. 5b depicts an exemplary sequence comprising four consecutive therapy sequences delivered along a continuous time axis according to embodiments of the invention.

[0161] Fig. 6 illustrates an exemplary control flow diagram for the ATP therapy according to embodiments of the present invention.

[0162] Fig. 7 depicts an exemplary detailed view of evaluation step 700 executed by the implantable medical device according to embodiments of the present invention.

[0163] Fig. 8 depicts an exemplary detailed view of evaluation step 800 executed by the implantable medical device according to embodiments of the present invention.

[0164] 23.167P-WO / / 20.03.2026Fig. 9 depicts an exemplary detailed view of evaluation step 900 executed by the implantable medical device according to embodiments of the present invention.

[0165] Fig. 10 illustrates the improvement in therapy success rate achieved by the ATP therapy according to the present invention.

[0166] 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 the implantable medical device housing for 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 dynamic adjustment of therapy sequences based on real-time cardiac event analysis. The memory unit 150 stores parameters such as post-pacing intervals, contributing to therapy sequence adjustments. The control unit 140 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.

[0167] 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.

[0168] After a therapy sequence TSi has been delivered, the detection unit may determine:

[0169] ■ The post-pacing interval Pli between the last delivered pulse of TSi and the first sensed cardiac event thereafter,

[0170] ■ The difference D of post-pacing intervals for consecutively delivered therapy sequences, D = Pli - Pl(i-l); and

[0171] ■ The phase offset of the tachycardia before and after Pli, that may be induced or modified by the delivered therapy sequence.

[0172] 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

[0173] 23.167P-WO / / 20.03.2026tachycardia 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 RS 1 220. 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). 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.

[0174] 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.

[0175] In an example, a sliding observation window 242 can be utilized to determine a redetection of a tachycardia, for instance if x-out-of-y inter-pulse intervals fall below a below a programmed tachycardia zone threshold.

[0176] Figure 3 shows a therapy sequence delivered along a continuous time axis during a tachycardia episode together with the observation windows and timing parameters used for analysis according to embodiments of the invention. Immediately prior to the therapy attempt, an observation window 210a is evaluated to confirm the rhythm and to determine the tachycardia cycle length TCL1 and a stability measure TCLs. In addition, a further observation window 350 ends at the first overlap with window 210a, providing additional context for estimating the ongoing tachycardia characteristics. For instance, the tachycardia is considered sufficiently stable if the difference between a mean

[0177] 23.167P-WO / / 20.03.2026tachycardia cycle length determined from the inter-pulse intervals from window 210a and a mean tachycardia cycle length determined from window 350 does not exceed a programmable threshold, e.g. 10 ms. The value 301 designates the cycle length TCL1 determined in these windows. TCL1 can be a mean tachycardia cycle length TCLm.

[0178] The depicted therapy sequence comprises two phases . A first burst phase 171 contains a number NS 1 of SI pulses that are equidistantly coupled relative to TCL1. The inter-pulse intervals of this burst phase are denoted 230 (SISI) and remain constant across the burst. According to one implementation, said burst parameters and an SI coupling factor are computed based on TCLm. A subsequent ramp phase 172 contains NS2 S2 pulses whose coupling intervals are successively shortened with respect to their immediate predecessors according to a ramp factor. The corresponding intervals are denoted 231 (S1S2 / S2S2) and decrease stepwise over the ramp. This two-portion structure allows the therapy to start with stable inter-pulse intervals and then tighten terminal coupling to increase the likelihood of interacting with the tachycardia circuit.

[0179] Following delivery of the last stimulus of the therapy sequence, the device identifies the first intrinsic event 360. The post-pacing interval 310 (PI) is measured as the time interval from the last delivered pulse of the series to this first intrinsic event 360. In parallel, the quantity 320 represents the intermittent interval between the last intrinsic event prior to the therapy sequence and the first intrinsic event after the therapy sequence . To support phase offset analysis, the device forms a virtual continuation 321 of the pre -therapy tachycardia at TCL1, extrapolating expected intrinsic event positions from the last pre -therapy intrinsic event. Based on the relationship between the intermittent interval 320 and TCL1 301, the device determines a phase offset 322 that represents the displacement of the post-therapy intrinsic timing relative to the virtually continued tachycardia. The phase offset can be expressed as a fraction or percentage of TCL1 (and, where useful, as an equivalent angular measure).

[0180] After the therapy sequence, a post-therapy observation window 300a is evaluated to verify persistence of tachycardia, to re-assess TCLm and TCLs under comparable conditions, and to validate the measurements for ATP therapy adaptation. When rhythm characteristics before and after ATP therapy are sufficiently similar, the combination of PI 310 and phase offset 322 provides a measure to the effectiveness of the therapy attempt.

[0181] Figure 4 illustrates an embodiment for determining the stability measure TCLs by the detection unit at the time the stability check is executed. The assessment is based on the most recent five detected cardiac events and thus the four immediately preceding inter-event intervals. Proceeding from the

[0182] 23.167P-WO / / 20.03.2026interval length of the current scenario 401, a tolerance band is spanned symmetrically around this interval; the band is delimited by an upper limit value 410a and a lower limit value 410b obtained by adding and subtracting, respectively, a programmable relative percentage of the last interval length — preferably within 4% to 30%, with 12% as a preferred value. The three direct predecessor interval lengths 402, 403, 404 are compared with this tolerance band: if all three lie within the band, the rhythm is classified as stable in the sense of TCLs; if any one of them lies outside, the rhythm is classified as unstable. In the example shown, interval 403 falls outside the tolerance band, so the evaluation classifies the rhythm as unstable.

[0183] Figure 5a illustrates an exemplary succession of therapy sequences delivered along a continuous time axis during one tachycardia episode, in which the control unit incrementally adapts the pulse counts of a two-portion sequence comprising a burst phase 171 with equidistant SI pulses (inter-pulse interval SISI) and a ramp phase 172 with S2 pulses whose coupling intervals (S1S2 / S2S2) are progressively shortened according to a programmed ramp factor; all coupling is normalized to the tachycardia cycle length (TCL1 which is for instance TCLm) via RSI and an inter-pulse-interval coupling factor for consistency with the application terminology. In the initial series of attempts 171a / 172a —> 171b / 172a —> 171c / 172a , the device increases the number of SI pulses NS1 in the burst phase from attempt to attempt while keeping the ramp configuration unchanged at 172a; after each attempt, the detection unit derives the phase offset from the intermittent interval using a virtual continuation of the pre -therapy tachycardia at TCL1, and entrainment is confirmed when the phase offset lies within the programmed detection window, the smallest burst count that achieves entrainment being recorded as Ns (depicted at 171c / 172a). Once Ns has been found and entrainment continues to be confirmed, the strategy holds NS1 constant at Ns (thus the burst portion remains 171c) and escalates the number of S2 pulses NS2 in the ramp portion across subsequent attempts ( 17 lc / 172b, then 171c / 172c, and so forth) to intensify terminal coupling.

[0184] Figure 5b depicts an exemplary sequence 501 comprising four consecutive therapy sequences 200a-200d delivered along a continuous time axis, beginning with recognition of tachycardia events 510 that trigger detection at time 500. Immediately prior to the first therapy sequence, the device evaluates observation window 210a (that for example comprises four inter-event intervals) to determine the initial tachycardia cycle length TCL initial, the mean tachycardia cycle length TCLm, and the stability measure TCLs, upon which the initial parameterization is applied with NS1 = 8 SI pulses in the burst and NS2 = 1 S2 pulse in the ramp phase (configuration 171a / 172a). The SISI inter-pulse intervals during the burst 171a are computed by the control unit using the programmed SI coupling factor referenced to TCLm from window 210. The terminal S1S2 interval (that is the coupling interval from the last S 1 pulse of the burst phase to the first S2 pulse from the ramp phase)

[0185] 23.167P-WO / / 20.03.2026in the ramp phase 172a is derived from the immediate preceding SISI via the programmed S2 ramp factor. After each delivered therapy sequence, at the first intrinsic event that follows the sequence (times 503a-503d), the device determines the post-pacing interval Pli, I being an index number, and its difference Di relative to the prior attempt (i.e., the difference D between two consecutive Pls), computes the phase offset using the intermittent interval and a virtual continuation of the pre -therapy rhythm, and performs validity checks as outlined for the next-attempt configuration (see e.g. Fig. 9). If the checks pass, the control unit obtains information as to whether entrainment was achieved and whether a loss-of-capture (LOC) scenario is indicated for the preceding therapy sequence. In the illustrated course, following 200a, the device continues to sense tachycardia and enters a redetection phase 503a (shown shortened), which for instance comprises at least eight intrinsic tachycardia events, typically more than twelve, in accordance with the device’s programmed redetection criterion. Because no entrainment is detected at 503a, the control strategy increases the burst count NS1 by the programmed increment Sl_Incr (here Sl lncr = 3) for the next attempt 200b, while the ramp remains consistent with the previous attempt. At 503b, entrainment is now recognized, yet tachycardia redetection still occurs (redetection phase 503b), so for 200c the device refreshes TCLm and TCLs from the new observation window 210c and keeps NS1 at the entrainment-achieving value Ns for the burst 171c, while increasing NS2 in the ramp 172c to intensify terminal coupling. After a further redetection in 503c, the device refreshes TCLm and TCLs from the new observation window 210d and delivers 200d analogously with the validated burst / ramp timing 17 ld / 172d (i.e. burst held at Ns, NS2 increased as permitted by limits). At 503d, the device senses a non-tachycardia event 511 at time 502, and the termination criterion (shown in shortened form, preferably an X-out-of-Y rule such as 5 of 12) is met so that 200d constitutes a successful ATP therapy for the episode, consistent with the adaptive evaluation and modification approach based on PI / D and phase-offset measurements according to embodiments of the invention.

[0186] Figure 6 illustrates an exemplary control flow diagram for the ATP therapy according to embodiments of the present invention. ATP is enabled through the programmer interface 600, which communicates the configuration to the implantable medical device. When a tachycardia condition is detected at 605, the control unit of the system confirms the rhythm characteristics (for example, tachycardia cycle length TCL or mean tachycardia cycle length TCLm and stability TCLs within an observation window) and selects dynamic ATP as the active therapy. The implantable medical device then sets initial parameters at 610, including, for example, the number of SI pulses NS 1, the number of S2 pulses NS2 and any initial ramp factor, and selects at 615 the scaling factor rs that is a percentage value and that determines the coupling interval RSI and the inter-pulse intervals of the burst phase SISI relative to TCL or TCLm. According to further aspects, the initial parameterization for dynamic ATP can be derived from (i) a formerly successful configuration recorded for the same patient under

[0187] 23.167P-WO / / 20.03.2026comparable tachycardia characteristics, and / or (ii) a population-based parameter set obtained by comparing current tachycardia features to stored data from other patients, such that the control unit loads a closest-match initial set before the first attempt of a sequence. Prior to delivery, the device may perform a suitability check for phase offset determination and optionally skip a therapy sequence or avoid certain parameter combinations of a therapy sequence if the current configuration would likely yield ambiguous phase offset (e.g., unfavorable intermittent-interval timing relative to TCLm), thereby preserving the diagnostic value of the next attempt. With these values, the implantable medical device delivers an initial therapy sequence at 616, which comprises a burst phase with equidistant inter-pulse intervals SISI and, optionally, a ramp phase in which the terminal intervals S1S2 or S2S2 are successively shortened according to the programmed ramp factor. Furthermore, the stability criterion for the tachycardia can be checked in 616.

[0188] During and after delivery of the initial therapy sequence, the implantable medical device executes a next-step evaluation at 700. In 720, the implantable medical device checks for termination of the tachycardia and performs redetection using the programmed termination criterion (for example, an X-out-of-Y intrinsic-interval rule). A successful termination ends the flow at 690. If the tachycardia persists, the implantable medical device performs the following measurements at 750: It determines the post-pacing interval PI from the last pulse of the preceding ATP therapy sequence to the first intrinsic cardiac event, computes the difference D between two consecutive post-pacing intervals across consecutive attempts, and derives the phase offset from the intermittent interval using the pre-therapy TCL or TCLm and a virtual continuation of the prior tachycardia pulses. These metrics allow the implantable medical device to confirm entrainment when the phase offset lies within a programmed detection window and to detect loss of capture LOC (for example, by PKTCLm and / or a negative difference D beyond a tolerance), thereby distinguishing effective, entrainment-achieving configurations from LOC-prone configurations.

[0189] The results from step 750 are used in step 800 to modify the next therapy sequence. Depending on programmed limits, timeouts and rhythm changes, the outcome at 800 selects one of four actions: therapy sequence optimization (continuation with another adapted therapy sequence), reset (reload of the initial configuration within the same therapy module), switch (escalation to a higher-priority therapy module) or break (suspension of further ATP therapy sequences for the ongoing episode). A check in step 760 figures out if further ATP attempts will be taken into consideration. If continued ATP is no longer effective or permitted, the flow ends at 694. Otherwise, the process will continue with step 615, which has been explained previously. The results will be handed to step 900, in which the control unit adapts at least one timing or other therapy sequence parameter — such as RSI, NS 1, NS2, SISI or the S2 ramp factor — based on the measured effects of the prior attempt. The term S2

[0190] 23.167P-WO / / 20.03.2026ramp refers to a pacing strategy used in ATP therapy, wherein an extra pulse S2 is delivered following a sequence of primary pacing pulses S 1. In this approach, the coupling interval of the S2 pulse is progressively shortened across successive attempts, effectively “ramping” the timing closer to the estimated refractory period of the tachycardia circuit. The newly configured therapy sequence is then delivered at 650.

[0191] The post-pacing interval PI and a difference D in two consecutive post-pacing intervals across ATP attempts may be monitored to recognize LOC (for example by PI < TCLm and / or a negative difference D beyond tolerance). According to embodiments, the primary adaptation criterion remains the phase offset; PI and difference D serve as complementary diagnostics that help discriminate entrainment from configurations prone to loss of capture.

[0192] In an example, for modification of a subsequent therapy sequence, the control unit is configured to perform at least one of the following:

[0193] increase the number of S 1 pulses NS 1 if a loss of capture has been previously identified, increasing the number of S2 pulses NS2 by one if entrainment has been confirmed but termination of the tachycardia has not occurred,

[0194] reducing the S2 ramp factor to shorten ramp intervals for a more aggressive approach to terminate tachycardia in case no loss of capture occurred,

[0195] increasing the S2 ramp factor to lengthen ramp intervals when loss of capture is detected during the ramp phase,

[0196] lengthening RS 1 and the corresponding SISI slightly if loss of capture is attributed to overly short coupling of the burst pulses.

[0197] After each delivered therapy sequence, the loop proceeds by determining a next-attempt configuration at 900, unless termination conditions 690 or 694 apply.

[0198] Throughout the episode, the implantable medical device measures and records data at 695 — such as RSI, NS1, NS2, SISI and S1S2 / S2S2 values, PI, difference D, phase offset and the determinations of entrainment and LOC — for later retrieval and analysis.

[0199] Figure 7 depicts an exemplary detail view of evaluation step 700 executed by the implantable medical device to determine the next step during or after an ongoing ATP therapy sequence. The flow begins at 701 after a previously delivered therapy sequence and the associated sensing of cardiac events. Immediately thereafter, the implantable medical device checks for termination and performs redetection at 720 using the programmed termination criterion (for example, an X-out-of-Y

[0200] 23.167P-WO / / 20.03.2026intrinsic -interval rule). A successful termination ends the flow at 690. If the tachycardia persists, and if the implantable medical device has performs the measurements at 750 (see Figure 6), the implantable medical device applies the step for modification of the next therapy sequence at 800. In 800, two sets of checks are applied: limit checks 810 and rhythm checks 820.

[0201] In the limit checks 810, the implantable medical device verifies whether predefined therapy constraints or safety conditions have been reached for the ongoing sequence. Such conditions can include a programmed maximum number of therapy sequences for the sequence, a maximum elapsed time since the initial detection of the tachycardia, or a previously recorded delivery of a shock therapy within the same episode. Further limits can reflect loss-of-capture (LOC) detections across consecutive attempts, parameter cappings reached in the preceding therapy sequence (for instance minimum allowable inter-pulse intervals in the burst or ramp phase, or a cap on the scaling factor rs that defines the coupling interval RSI), or other device-specific constraints that render a further ATP attempt impractical or inadvisable.

[0202] In the rhythm checks 820, the implantable medical device assesses whether the present tachycardia is still suitable for continuation with dynamic ATP under the assumptions of the current therapy module. To this end, the implantable medical device compares the mean tachycardia cycle length TCLm measured immediately prior to the last therapy sequence with the initial TCLm of the sequence to detect substantial changes in tachycardia cycle length, and it verifies continued stability TCLs within the observation window. Additionally, the implantable medical device can test a minimum TCLm criterion to exclude rhythms that are too fast for safe and effective ATP delivery under the current settings.

[0203] Checks 810 and 820 are followed by decision step 760 for termination of further ATP attempts and subsequent steps according to Figure 6.

[0204] Figure 8 depicts an exemplary detailed view of evaluation step 800 that determines whether another ATP therapy sequence is delivered and, if so, under which constraints. The process is entered at the step for modification of the next therapy sequence 800 once the implantable medical device has completed redetection and measurements (including PI, difference D and phase offset). Within 800, a first group of limit checks 810 determines whether configured therapy boundaries or safety conditions have been reached. In one exemplary check, the implantable medical device determines at 811 whether the programmed maximum number of pulses for the current therapy sequence would be exceeded by issuing a further attempt. Alternatively or in addition, the implantable medical device determines at 811 whether the programmed maximum number of therapy sequences would be

[0205] 23.167P-WO / / 20.03.2026exceeded by issuing a further attempt. Fulfilment of this condition contributes a potential outcome of switch for the resolution in 800. At 812, a timer started with initial tachycardia detection is compared against a programmed maximum; if the maximum time is exceeded and a shock therapy is configured as a follow-up, the implantable medical device marks a potential break so that no further ATP attempts are issued in the ongoing episode. At 813, the implantable medical device tests for a programmable count of consecutive attempts with detected loss of capture (LOC). The satisfaction of this condition results a potential switch. At 814, the implantable medical device inspects whether the immediately preceding therapy sequence had to be limited by any of the programmed parameter bounds — such as reaching a maximum number of SI pulses NSlmax in the burst phase, reaching a minimum allowable inter-pulse interval S 1 S 1 in the burst phase Tmin burst, or reaching a minimum allowable inter-pulse interval S1S2 / S2S2 in the ramp phase Tmin_ramp. If any of such limitations is present, switch is recorded as a potential outcome. At 815, the implantable medical device applies additional limitation checks for the preceding therapy sequence: For example, ramp-phase intervals must not exceed those of the burst phase, the scaling factor rs must not fall below a programmed maximum relative share of TCLm (ensuring the coupling interval RSI remains capable of capturing myocardium toward the reentry circuit), and the S2 ramp factor is bounded above by a programmed maximum to ensure successive shortening. If any of these constraints is met, a potential switch is indicated, whereas certain configurations can also mark a potential break when ATP would be weaker than a therapy already delivered. At 816, if shock therapy has already been delivered in the current episode, the implantable medical device records a potential break to prevent issuing a weaker therapy thereafter. Finally, at 817, if a previous comparable therapy modality caused a significant acceleration of the rhythm (for example a change from a VT zone into a VF zone), a potential switch is recorded.

[0206] A second group of rhythm checks 820 assesses whether rhythm characteristics of the present tachycardia remains suitable for ATP under the assumptions of the current invention. In 821, the implantable medical device compares the mean tachycardia cycle length TCLm immediately prior to the most recent therapy sequence with the initial TCLm of the ongoing sequence. Exceeding programmed relative and / or absolute deviation limits indicates a substantial rhythm change and results in a potential reset. In 822, the implantable medical device evaluates stability (for example TCLs within limits in the observation window). Failure of the stability test also contributes to a potential reset. In 823, the implantable medical device verifies that TCLm does not fall below a programmed minimal value. In case the minimal value criterion is not fulfilled, a potential break is recorded to exclude rhythms that are too fast for safe and effective ATP delivery under the current settings.

[0207] 23.167P-WO / / 20.03.2026Once all checks in 810 and 820 have been applied, the process proceeds to the resolution stage beginning at 801, where the outcomes of the previous steps is reduced to a single action. If at least one potential break is present, 830 resolves the result of 800 to break, and the episode leads to 694 so that no further ATP therapy sequences are attempted in the ongoing episode. If no break is present but at least one potential switch is present, 831 resolves the result of 800 to switch and the control continues to 890, where a higher-priority therapy module is selected. If neither break nor switch applies but at least one potential reset is present, 832 resolves the result of 800 to reset and the control advances to 891, where the initial parameterization for the current therapy module is reloaded and a new therapy sequence is started. If none of the conditions applies, the default outcome of 800 is sequence optimization, forwarded to 892, whereby the implantable medical device continues the ongoing therapy sequence with another adapted therapy sequence whose configuration is to be determined under the next-attempt configuration step (see 900).

[0208] Figure 9 depicts an exemplary detailed view of the next-attempt configuration 900 executed after each delivered therapy sequence.

[0209] Coming from step 892, the process begins with a validity check at 901, in which the implantable medical device confirms that the post-pacing interval PI can be determined from the last pulse of the preceding therapy sequence to the first intrinsic cardiac event and that the sensing context is suitable for using PI and related quantities (for example first event is intrinsic, not paced). When the basic prerequisites are met, the implantable medical device evaluates loss of capture (LOC) in 905-907. In 906, LOC is detected if PI is shorter than TCLm, which indicates that the last pulse encountered refractory tissue and failed to advance the rhythm. In 907, LOC may alternatively (or additionally) be inferred by a negative difference D between two consecutive post-pacing intervals beyond a programmed tolerance, computed from the difference between the current PI and the PI of the preceding attempt, provided both PI values are valid. These complementary criteria allow robust recognition of LOC both from absolute post-pacing timing and from the trend across consecutive attempts.

[0210] In parallel, the implantable medical device derives and validates the phase offset at 910. To this end, the control unit determines the intermittent interval between the last intrinsic event prior to the preceding therapy sequence and the first intrinsic event thereafter, virtually continues the pre -therapy tachycardia using TCL or TCLm, and computes the phase offset as the deviation (offset time interval) between the expected and the observed event positions. A validity evaluation ensures that the mean tachycardia cycle length TCLm measured in the observation window prior to the last therapy sequence is sufficiently similar to that of the subsequent observation window, i.e. TCLm of the

[0211] 23.167P-WO / / 20.03.2026observation window before the last therapy sequence does not deviate from that of the subsequent window by more than a programmed margin, so that the phase offset reflects a comparable rhythm. When valid, phase offset values within a programmable phase window, for example 10% < phase offset < 90%, are treated as evidence of entrainment by the preceding therapy sequence, whereas values near 0% or 100% (or outside the window) indicate absent entrainment or ambiguity and prompt adaptation.

[0212] Before selecting concrete modifications, the algorithm may consult a proximity check at 915 to determine whether the number of S2 pulses NS2 used in the preceding therapy sequence was already near a programmed maximum (for example NS2max - 1).

[0213] Based on the measurement outcomes and limit checks, the control unit generates the parameter set for the next therapy sequence using the adaptation steps at 920-924. If entrainment has not yet been achieved, the implantable medical device increases the number of S 1 pulses in the burst phase at 920 by adding a programmed increment to NS 1, thereby improving the likelihood that successive stimuli capture myocardium toward the reentry circuit. If entrainment is present but termination has not occurred and additional aggressiveness in the terminal part of the therapy sequence is warranted, the implantable medical device increases the number of S2 pulses at 921. When the ramp requires stronger shortening to interact with the reentrant circuit, the implantable medical device reduces the S2 ramp factor at 922 so that the S 1 S2 / S2S2 intervals become successively shorter. Conversely, when LOC is detected during the ramp while entrainment is otherwise present, the implantable medical device relaxes the ramp by increasing the ramp factor at 923, thereby lengthening S1S2 / S2S2 to avoid refractory collisions. If LOC is attributed to coupling that is too aggressive already in the burst, the implantable medical device slows the burst coupling at 924 by increasing the scaling factor rs, which lengthens RSI and the ensuing SISI so that capture is re-established without abandoning the closed-loop strategy.

[0214] The measurement of the PI and the phase offset to evaluate the effectiveness of the ATP can be used in combination, parallel or as alternatives. That may have consequences to the available parameters for evaluation of the ATP success and thus modification means for subsequent therapy sequences.

[0215] Finally, comping from step 890, which resolves the result of 800 to switch, the algorithm checks whether the therapy plan foresees ATP as the succeeding higher therapy module at 940. If so, the implantable medical device may select the initial parameterization of that module at 941 to configure the next attempt. That may be a pre-programmed configuration for the purpose of applying ATP as escalation therapy measure. The parameter set produced by the logic of Figure 9 is then handed to

[0216] 23.167P-WO / / 20.03.2026the delivery step of the main flow (see Figure 6), ensuring that each subsequent therapy sequence reflects the latest PI, difference D and phase offset evidence together with applicable limits.

[0217] Figure 10 illustrates the improvement in therapy success rate achieved by the ATP therapy according to the present invention. It shows two graphs that each depict therapy success rates: Graph 1001 represents the success rate of a therapy sequence including a burst and a ramp phase, with SI pulses followed by at least one S2 pulse and including feedback / adaptation mechanisms according to embodiments of the invention — Graph 1002 represents the success rate of a therapy sequence that delivers only SI pulses without feedback and merely increments the pulse count between attempts. The ordinate shows the success rate (0...1), while the abscissa shows ca_mod, a dimensionless measure of the repolarization behavior of diseased cells in the isthmus of an infarct. Across the investigated ca_mod range, the curve for the ATP therapy according to the intention (S1BS2R, i.e. Sl-burst-then-S2-ramp) rises earlier and reaches a higher plateau — approaching unity in the upper ca_mod range — whereas the SI -only approach exhibits delayed onset and clearly lower success throughout most of the domain.

[0218] 23.167P-WO / / 20.03.2026Reference Numeral List

[0219] 100 Implantable medical device (IMD)

[0220] 110 Heart

[0221] 111 Electrode pole(s)

[0222] 120 Stimulation unit

[0223] 130 Detection unit

[0224] 140 Control unit

[0225] 150 Memory unit

[0226] 170 Therapy sequence TSi

[0227] 171 Burst phase

[0228] 172 Ramp phase

[0229] 200 Therapy sequence

[0230] 200a Therapy sequence (example course)

[0231] 200b Therapy sequence (example course)

[0232] 200c Therapy sequence (example course)

[0233] 200d Therapy sequence (example course)

[0234] 209 Baseline cycle length CL

[0235] 210 Tachycardia cycle length TCL

[0236] 210a Pre-therapy observation window

[0237] 210b Observation window for confirming tachycardia

[0238] 210c Observation window prior to a later attempt

[0239] 21 Od Observation window prior to last attempt before tachycardia termination 211 Tachycardia cycle length after an attempt

[0240] 211b Post-attempt observation window

[0241] 212 First detected intrinsic cardiac event

[0242] 220 Coupling interval RS 1

[0243] 230 Inter-pulse interval SISI (burst)

[0244] 231 Inter-pulse interval S1S2 / S2S2 (ramp)

[0245] 242 Sliding observation window for redetection criterion

[0246] 300a Post-therapy observation window

[0247] 301 TCL1 / TCL initial

[0248] 310 Post-pacing interval PI

[0249] 320 Intermittent interval

[0250] 321 Virtual continuation of pre-therapy tachycardia

[0251] 23.167P-WO / / 20.03.2026Phase offset

[0252] 0 Additional pre-therapy observation window

[0253] 0 First intrinsic cardiac event after a therapy sequence 1 Current interval length

[0254] Predecessor interval length

[0255] 3 Predecessor interval length

[0256] Predecessor interval length

[0257] 0a Upper limit of tolerance band

[0258] 0b Lower limit of tolerance band

[0259] 0 Detection time

[0260] 1 Block comprising four consecutive therapy sequences Detection time

[0261] 3a Redetection phase / first-event marker after sequence 3b Redetection phase / first-event marker after sequence 3c Redetection phase / first-event marker after sequence 3d Redetection phase / first-event marker after sequence 0 Recognized tachycardia events triggering detection 1 Non-tachycardia event

[0262] 1a Burst-phase configuration

[0263] 1b Burst-phase configuration

[0264] 1c Burst-phase configuration

[0265] Id Burst-phase configuration

[0266] a Ramp-phase configuration

[0267] b Ramp-phase configuration

[0268] c Ramp-phase configuration

[0269] d Ramp-phase configuration

[0270] 0 Programmer interface

[0271] 5 Tachycardia detection step

[0272] 0 Set initial parameters

[0273] 5 Scaling factor rs

[0274] 6 Deliver initial therapy sequence

[0275] 0 Deliver newly configured therapy sequence

[0276] 0 Termination (successful)

[0277] End (no further ATP)

[0278] 5 Data logging / storage

[0279] 23.167P-WO / / 20.03.2026Next-step evaluation

[0280] Entry to evaluation after sequence

[0281] Termination / redetection check

[0282] Measurements: PI, D, phase offset

[0283] Decision to continue ATP attempts

[0284] Modification step for next sequence (resolution)

[0285] Limit checks

[0286] Check max pulses / sequences (potential switch)

[0287] Max elapsed time (potential break)

[0288] Consecutive loss-of-capture (LOC) attempts (potential switch) Parameter bound hit (potential switch)

[0289] Additional limits (potential switch / break)

[0290] Shock already delivered (potential break)

[0291] Significant acceleration (e.g., VT^VF) (potential switch) Rhythm checks

[0292] TCLm change check (potential reset)

[0293] Stability check (potential reset)

[0294] Minimum TCLm check (potential break)

[0295] Resolve to break

[0296] Resolve to switch

[0297] Resolve to reset

[0298] Select higher-priority therapy module

[0299] Reload initial parameterization

[0300] Sequence optimization

[0301] Next-attempt configuration

[0302] Validity check for Pl / sensing context

[0303] LOC evaluation block

[0304] LOC by PI < TCLm

[0305] LOC by negative D beyond tolerance

[0306] Derive & validate phase offset

[0307] proximity check (NS2 near max)

[0308] Increase NS1

[0309] Increase NS2

[0310] Reduce S2 ramp factor

[0311] Increase S2 ramp factor

[0312] 23.167P-WO / / 20.03.2026924 Increase rs (lengthen RSI & S1S1)

[0313] 940 Check if succeeding module is ATP

[0314] 941 Select initial parameterization of succeeding module

[0315] 1001 Success-rate curve: Sl+S2-ramp with feedback / adaptation (S1BS2R) 1002 Success-rate curve: SI -only (no feedback)

[0316] 23.167P-WO / / 20.03.2026

Claims

Claims1. Implantable medical device (IMD 100) for anti -tachycardia pacing (ATP) of a heart, comprising:- at least one electrode pole (111) configured to sense electrical signals of the heart and apply electrical pulses to the heart,- a stimulation unit (120), configured to deliver the electrical pulses to the heart via the electrode pole (111), wherein the stimulation unit (120) is configured to deliver at least one therapy sequence to the heart, the therapy sequence 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 and to derive at least one parameter to adjust the therapy sequence based on the events, characterized in thatthe stimulation unit (120) is configured to deliver a first therapy sequence TS1 to the heart if the detection unit (130) detects a first tachycardia condition based on a plurality of first events,and if the detection unit (130) detects a second tachycardia condition based on a plurality of second events after delivery of the first therapy sequence TS1,the detection unit (130) is configured to determine a first post-pacing interval PI1 between the last delivered pulse of the first therapy sequence TS 1 and a first detected intrinsic cardiac event after the last delivered pulse of the first therapy sequence TS1, wherein the stimulation unit (120) is configured to deliver a second therapy sequence TS2 to the heart,and if the detection unit (130) detects a third tachycardia condition based on a plurality of third events after delivery of the second therapy sequence TS2, the detection unit (130) is configured to determine a second post-pacing interval PI2 between the last delivered pulse of the second therapy sequence TS2 and a first detected intrinsic cardiac event after the last delivered pulse of the second therapy sequence TS2, wherein the control unit (140) is configured to compute a first relation parameter RP1 between PI 1 and PI2,23.167P-WO / / 20.03.2026and wherein the detection unit (130) is configured to detect at least one phase offset between the first events and the second events, and / or between the second events and the third events,wherein the control unit (140) is configured to generate a third therapy sequence TS3 depending on the first relation parameter RP1, and / orwherein the control unit (140) is configured to generate the second therapy sequence TS2 and / or the third therapy sequence TS3 based on the phase offset.

2. IMD according to claim 1, wherein a tachycardia condition is detected if- the time intervals between the events have a tachycardia cycle length TCL shorter than a tachycardia threshold, and if- the time intervals between the events fulfill at least one stability parameter.

3. IMD according to claim 1 or 2, wherein the control unit (140) is configured to generate an inter-pulse-interval IPIi- between at least two of a plurality of electrical pulses of a therapy sequence if the therapy sequence TSi comprises more than one pulse, or- between a pulse of the tachycardia and the first pulse of the therapy sequence if the therapy sequence TSi comprises one pulse,wherein the inter-pulse-interval IPIi is shorter than the tachycardia cycle length TCL of the preceding events.

4. IMD according to at least one of the preceding claims, wherein the relation parameter is a difference D between two successively measured post-pacing intervals Pli.

5. IMD according to at least one of the preceding claims, wherein the detection unit (130) is configured to determine the phase offset if the time intervals between the first events and the time intervals between the second events have a similar length, wherein a similar length is confirmed if a difference of an interval length of the time intervals between the first events and the interval length of the time intervals between the second events is smaller than a threshold difference.

6. IMD according to at least one of the preceding claims, wherein the detection unit (130) is configured to determine the phase offset by23.167P-WO / / 20.03.2026- virtually continuing the first events by adding a plurality of estimated events in succession to the first events, the estimated events each having a first tachycardia cycle length TCL1 to the preceding event,- calculate an offset time interval between one estimated event and one neighboring second event,- determine the phase offset based on the offset time interval in relation to the first tachycardia cycle length TCL1.

7. IMD according to at least one of the claims 1 to 5, wherein the detection unit (130) is configured to determine the phase offset by- Calculating an intermittent interval between the last event of the first events and the first event of the second events,- Dividing the intermittent interval by the first tachycardia cycle length TCL1, - calculating the remainder of the division, wherein the remainder is defined as offset time interval,- determine the phase offset based on the offset time interval in relation to the first tachycardia cycle length TCL1.

8. IMD according to at least one of the preceding claims, wherein the control unit (140) is configured to generate at least one therapy sequence TSi by adjusting at least one of the following parameters:- a duration of the therapy sequence,- a number of therapy sequence of the therapy sequence,- a number of pulses Ni of a therapy sequence,- an inter-pulse-interval IPIi between at least two pulses of a therapy sequence, - a coupling interval RSi between a last pulse of the events having a tachycardia condition and the first pulse of a therapy sequence.

9. IMD according to claims 8 and 4, wherein the at least one therapy sequence TSi comprises a number of pulses Ni having a first inter-pulse-interval IPIi, followed by at least one further pulse S2, wherein an inter-pulse-interval IPIis2 between the last pulse of the at least one Ni pulses and the at least one further pulse S2 is shorter than IPIi, and wherein the control unit (140) is configured to determine IPIis2 on the basis of the difference D and / or on the basis of the phase offset.23.167P-WO / / 20.03.202610. IMD according to claim 9, wherein the at least one therapy sequence TSi comprises a plurality of further pulses S2... Sn, wherein the inter-pulse-intervals IPIis2... IPIisn decrease in length, wherein the control unit (140) is configured to determine the lengths of the interpulse-intervals IPIis2... IPIisn on the basis of the difference D and / or on the basis of the phase offset.

11. IMD according to claim 10, wherein the control unit (140) is configured to determine the decrease in lengths by successively shortening each inter-pulse-interval IPIis2... IPIisn by a pre-determined time period or by a percentage value PV in relation to the preceding interpulse interval.

12. IMD according to at least one of the claims 8 to 11 and 4, wherein the at least one therapy sequence TSi comprises a number of pulses Ni, wherein the control unit (140) is configured to determine Ni on the basis of the phase offset and / or on the basis of the difference D.

13. IMD according to at least one of the claims 8 to 12, wherein the control unit (140) is configured to store the smallest number of pulses Ns of a therapy sequence TSs out of a number of therapy sequences n, wherein Ns leads to a longest post-pacing interval Pls between the last pulse of the therapy sequence TSs and a first detected intrinsic cardiac event after the last pulse of the therapy sequence out of a number n of post-pacing intervals.

14. IMD according to at least one of the preceding claims, wherein the control unit (140) is configured to confirm a positive effect of the first therapy sequence if the phase offset is lower than an upper threshold or greater than a lower threshold, wherein the control unit (140) is configured to store the parameters of the associated therapy sequence in a memory unit (150).

15. Method for operating an implantable medical device (IMD 100) for stimulating a human or animal heart, characterized by the following steps:- detect a first tachycardia condition based on a plurality of first events in an electrical signal of the heart,- deliver a first therapy sequence TSI (200, 301) comprising at least one electrical pulse to the heart,- if a second tachycardia condition is detected based on a plurality of second events after delivery of the first therapy sequence TSI, measure a first post-pacing interval23.167P-WO / / 20.03.2026PI 1 (310) between the last pulse of the first therapy sequence TS 1 and a first detected intrinsic cardiac event (212) after the last pulse of the first therapy sequence TS 1, - deliver a second therapy sequence TS2 to the heart,- if a third tachycardia condition is detected based on a plurality of third events after delivery of the second therapy sequence TS2, measure a second post-pacing interval PI2 (310) between the last pulse of the second therapy sequence TS2 and a first detected intrinsic cardiac event (212) after the last pulse of the second therapy sequence TS2,- compute a first relation parameter RP1 between PI1 and PI2,- detect at least one phase offset between the first events and the second events, and / or between the second events and the third events,- generate a third therapy sequence TS3 depending on the first relation parameter RP 1 , - generate the second therapy sequence TS2 and / or the third therapy sequence TS3 based on the phase offset.23.167P-WO / / 20.03.2026

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