Anti-tachycardia pacing implantable medical device

Abstract

An implantable medical device configured for anti-tachycardia pacing comprises at least one electrode pole designed to sense cardiac electrical signals and deliver electrical pulses to the heart. The device includes a stimulation unit that sends therapy sequences containing one or more pulses through the electrode pole. A detection unit monitors these electrical signals to identify cardiac events, analyze intervals between them, and detect tachycardia conditions. A control unit generates therapy sequences and adjusts therapy parameters based on detected events. The stimulation unit delivers an initial therapy sequence upon detection of a first tachycardia condition. If a subsequent second tachycardia is detected after the first therapy, a post-pacing interval is measured. The stimulation unit then delivers a second therapy sequence, with further tachycardia detection prompting measurement of an additional post-pacing interval. The control unit calculates a relation parameter from these intervals and generates a third therapy sequence accordingly.

Description

[0001] Anmelder: BIOTRONIK SE & Co. KG

[0002] Datum: 09.03.2026

[0003] Unser Zeichen: 23.162P-WO

[0004] ANTI-TACHYCARDIA PACING IMPLANTABLE MEDICAL DEVICE

[0005] The present application generally relates to an implantable medical device for anti -tachycardia (ATP) pacing of a heart, and more particularly to a stimulation unit, detection unit, and control unit configured for delivering and adjusting therapy sequences based on detected cardiac events and post-pacing intervals.

[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 monomorphic ventricular tachycardia (VT) 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 VT cycle length in an attempt to interrupt the reentrant circuit responsible for VT.

[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 VT at the time of therapy delivery. As a result, ATP may fail to terminate VT 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] Accordingly, there is a need for improved methods and systems that dynamically tailor ATP therapy to the patient’s real-time arrhythmic state. In particular, there is a need for approaches that utilizetiming 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 VT termination, reduce the number of unsuccessful attempts, and minimize the need for high-energy shocks.

[0010] 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.

[0011] The formulated problem is solved by the presented device and method according to independent claims 1 and 14, and by embodiments described in the dependent claims and the accompanying figure description.

[0012] According to the invention, an implantable medical device (IMD) for anti-tachycardia pacing (ATP) of a heart is proposed, comprising:

[0013] - At least one electrode pole, configured to sense electrical signals of the heart and apply electrical pulses to the heart.

[0014] - 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.

[0015] - A detection unit, configured to:

[0016] - detect events in the sensed electrical signals,

[0017] - analyze time intervals between the events, and

[0018] - detect a tachycardia condition based on the events.

[0019] - A control unit, configured to:

[0020] i. Generate at least one therapy sequence TSi.

[0021] ii. Derive at least one parameter to adjust the therapy sequence TSi based on the detected events.

[0022] The stimulation unit is configured to deliver a first therapy sequence TSI, 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.

[0023] 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

[0024] 23.162P-WO / 09.03.2026PI1 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] Based on the first relation parameter RP1, the control unit is configured to generate a third therapy sequence TS3.

[0029] 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

[0030] - The time intervals between the events fulfill at least one stability parameter.

[0031] In an embodiment, the implantable device determines 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 autocorrelationbased parameters to assess the stability consistency of tachycardia events before confirming a tachycardia condition.

[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 150bpm. VT zone 2 is defined as tachycardias equal to or greater than 187bpm.

[0035] 23.162P-WO / 09.03.2026VF zone 3 is defined as tachycardias equal to or greater than 222bpm.

[0036] 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.

[0037] Implementing inter-pulse intervals shorter than the tachycardia cycle length improves the likelihood of successfully interrupting tachycardias, thereby enhancing therapy efficacy.

[0038] According to an embodiment of the present invention, the relation parameter is a difference D between two successively measured post-pacing intervals Pli.

[0039] 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.

[0040] 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:

[0041] - A duration of the therapy sequence,

[0042] - A number of pulses of a therapy sequence,

[0043] - An inter-pulse interval between at least two pulses of a therapy sequence,

[0044] - A coupling interval between the last pulse of the events having a tachycardia condition and the first pulse of a therapy sequence,

[0045] - A maximum number of therapy sequences,

[0046] - A maximum duration of the therapy sequence,

[0047] - A minimum and / or maximum duration between successive therapy sequences.

[0048] According to an embodiment of the present invention,

[0049] - The number of therapy sequences is 10, 20, 30 or 40,

[0050] - The duration of a therapy sequence ranges between 60s to 3600s.

[0051] - The minimum duration between successive therapy sequences is 0.6s.

[0052] 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:

[0053] 23.162P-WO / 09.03.2026- a maximum number of therapy sequences,

[0054] - a maximum duration of the therapy sequence,

[0055] - a minimum and / or maximum duration between therapy sequences.

[0056] 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.

[0057] According to an embodiment, a maximum duration of the therapy sequence is 3600s.

[0058] Moreover, according to an aspect, the minimum duration is 600ms.

[0059] 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.

[0060] In an embodiment of the invention,

[0061] - the coupling interval RSi is computed by rs*TCL, whereby 0.5 < rs < 1;

[0062] - the inter-pulse-interval IPIi is computed by ipi*TCL, whereby ipi < rs,

[0063] - whereby all inter-pulse-intervals of a therapy sequence are of equal length.

[0064] 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.

[0065] Moreover, according to an aspect of the invention, the control unit is configured to generate an inter pulse interval IPIi

[0066] 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

[0067] between a pulse of the tachycardia and the first pulse of the therapy sequence if the therapy sequence TSi comprises one pulse,

[0068] wherein the inter-pulse-interval IPIi is shorter than the tachycardia cycle length TCL of the preceding events.

[0069] Moreover, according to an embodiment of the invention, wherein if

[0070] Ni >Ni-l, and Pli > PIi-1,

[0071] 23.162P-WO / 09.03.2026the control unit is configured to adjust at least one subsequent therapy sequence by Ni+1 > Ni, wherein

[0072] Ni- 1 = number of pulses of a preceding therapy sequence,

[0073] Ni+1 = number of pulses of a subsequent therapy sequence,

[0074] Pli = post-pacing interval between the last pulse of the therapy sequence and a first detected intrinsic cardiac event after the last pulse of the therapy sequence,

[0075] PIi-1 = post-pacing interval between the last pulse of the preceding therapy sequence and a first detected intrinsic cardiac event after the last pulse of the preceding therapy sequence.

[0076] In other words, if the current therapy sequence comprises more pulses than the preceding sequence and the corresponding post-pacing interval is longer, the control unit increases the number of pulses in subsequent therapy sequences accordingly.

[0077] This dynamic increment in pulse number based on post-pacing interval trends facilitates controlled therapy adjustments, potentially improving termination the tachycardia condition.

[0078] According to an embodiment, the calculation of Pli > Pli- 1 comprises a measurement tolerance of approximately 10ms.

[0079] In an embodiment, the control unit is configured to apply no further therapy sequence if Pli < Pli- 1.

[0080] In other words, the control unit refrains from delivering any further therapy sequences if the postpacing interval measured after the current therapy is shorter than that of the preceding therapy sequence.

[0081] According to an embodiment of the present invention, Pli > Pli- 1 comprises a minimum tolerance, which is for example 10ms. As an alternative, the minimum tolerance can be computed by x*(PIi-l - PIi-2), wherein x = 0.1, 0.2, 0.3, or 0.4. Then, the condition for applying no further therapy sequence is Pli < Pli- 1 plus or minus tolerance x*(PIi-l - Pli -2).

[0082] Ceasing therapy when post-pacing intervals shorten prevents ineffective or potentially harmful over-stimulation, improving patient safety and conserving device resources.

[0083] 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

[0084] 23.162P-WO / 09.03.2026of 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.

[0085] Retaining the minimal effective pulse count that maximizes post-pacing interval allows the device to optimize therapy efficiency, reducing unnecessary stimulation while maintaining efficacy.

[0086] 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.

[0087] If entrainment is detected, this fact is reported along with the corresponding therapy sequence parameters, for example:

[0088] - to the control unit, which takes this into account when configuring subsequent therapy sequences, - made available to external entities,

[0089] - stored for later processing or retrieval.

[0090] In particular, the value Ns is made available for further processing.

[0091] According to aspects of the present invention, once the difference between PI values for successive therapy sequences with differing numbers of pulses falls below the adjustable threshold, the minimum number of pulses Ns for which this condition holds is identified. For instance, subsequent therapy sequences are generated with Ns initial pulses followed by at least one additional pulse, wherein the intervals of these additional pulses are preferably shorter than at least one interval within the first Ns pulses. If it is observed that differences between PI values of successive therapy sequences with the same or increasing pulse counts are less than the adjustable threshold, including negative differences, at least one inter-pulse interval of a subsequent therapy sequence is increased relative to the corresponding therapy sequence.

[0092] In an embodiment, 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.

[0093] 23.162P-WO / 09.03.2026In other words, the at least one therapy sequence comprises a series of pulses with a defined first inter-pulse interval, followed by at least one additional pulse delivered with a shorter inter-pulse interval relative to the preceding pulses.

[0094] Introducing a shorter interval pulse following a series may improve the probability of terminating a tachycardia condition.

[0095] According to an embodiment, the at least one therapy sequence TSi comprises at least one further pulse S3, wherein an inter-pulse-interval IPIis3 between S2 and S3 is shorter than IPIis2. According to a further aspect, none of the inter-pulse- intervals IPIs2, IPIs3 is shorter than a predefined limit. This predefined limit is for example 150ms.

[0096] In an embodiment, IPIis2 is configured to be shorter than IPIi by a programmable range of 1% to 50%. Preferably, IPIis2 is configured to be shorter than IPIi by a programmable range of 5% up to 20% by steps of 5 %.

[0097] In an embodiment, Ni is equal to Ns, or in other words, the number of pulses in the therapy sequence corresponds to the stored smallest effective number of pulses previously identified as yielding the longest post-pacing interval.

[0098] This ensures application of the most efficient pulse count, maintaining therapy effectiveness and minimizing unnecessary energy consumption.

[0099] Moreover, according to an embodiment of the present invention, if

[0100] Ni >Ni-l, and Pli < PIi-1,

[0101] wherein

[0102] Ni is the number of pulses of a therapy sequence,

[0103] Ni-1 is the number of pulses of a preceding therapy sequence,

[0104] Pli is the post-pacing interval between the last pulse of the therapy sequence and a first detected intrinsic cardiac event after the last pulse of the therapy sequence, and

[0105] Pli- 1 is the post-pacing interval between the last pulse of the preceding therapy sequence and a first detected intrinsic cardiac event after the last pulse of the preceding therapy sequence, then the control unit is configured to generate a subsequent therapy sequence TSi+1 by IPIi+1 > IPIi, wherein

[0106] IPIi+1 is at least one inter-pulse-interval between at least two pulses of TSi+1, and

[0107] 23.162P-WO / 09.03.2026IPIi is at least one inter-pulse-interval between at least two pulses of TSi.

[0108] In other words, if a therapy sequence has more pulses than the preceding one but results in a shorter post-pacing interval, the control unit increases the inter-pulse interval for subsequent therapy sequences.

[0109] Adjusting inter-pulse intervals based on feedback adapts pacing timing to optimize tachycardia termination success.

[0110] According to an embodiment, if the control unit is configured to generate a subsequent therapy sequence TSi+1 by IPIi+1 > IPIi, the minimal allowable inter-pulse-interval length shall be raised.

[0111] According to an embodiment of the present invention, the IMD is a cardiac pacemaker, an implantable cardioverter-defibrillator (I CD), a cardiac rhythm management therapy (CRT) device, or a conduction system pacing (CSP) device.

[0112] 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:

[0113] - Detect a first tachycardia condition based on a plurality of first events in an electrical signal of the heart.

[0114] - Deliver a first therapy sequence TSI, comprising at least one electrical pulse to the heart.

[0115] - 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 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.

[0116] - 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.

[0117] - Compute a first relation parameter RP1 between PI1 and PI2.

[0118] 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.

[0119] 23.162P-WO / 09.03.2026According to an embodiment of the inventive method, the relation parameter is a difference D between two successively measured post-pacing intervals Pli.

[0120] In other words, the relation parameter used for adjusting therapy is defined as the difference between two successively measured post-pacing intervals.

[0121] 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.

[0122] 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 devices 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.

[0123] 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 anti-tachycardia therapy and whether PI measurements should be undertaken. Differences between successive PI 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.

[0124] 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 between 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.

[0125] According to an example, valid intrinsic events following the last pulse in each series are identified using morphological and temporal criteria to ensure accurate PI measurement. Therapeutic success

[0126] 23.162P-WO / 09.03.2026is indicated by termination of tachycardia following one of the pulse series. PI values and tachycardia characteristics before and after pulse series can be stored, can be accessed by external programmers, and may be transmitted via home monitoring systems.

[0127] According to an embodiment, evaluation of multiple PI measurements and therapy adjustment derivations can be conducted externally, for example, by clinical specialists or via programming and monitoring devices.

[0128] According to an embodiment, at least one coupling interval and / or at least one inter-pulse interval are defined as a fraction of the tachycardia cycle length, meeting specific ratio constraints.

[0129] For instance, simulations demonstrate that increasing pulse counts yield PI values that rise and saturate, with the lowest pulse count achieving saturation representing effective entrainment. Data related to entrainment behavior can be used by the control unit for further therapy parameterization, external evaluation, and storage.

[0130] In an embodiment, the control unit is configured to stop delivering further therapy sequences when either no tachycardias are detected, a predefined maximum number of therapy sequences has been delivered, or a maximum elapsed time since the first therapy sequence has passed.

[0131] According to at least one further aspect of the invention, further implementations extend pulse series beyond entrainment with additional pulses delivered at shorter inter-pulse intervals than the initial pulses, observing minimum allowable pulse interval constraints. Adaptation of therapy parameters such as minimum permissible pulse intervals is performed based on PI responses to pulse count increases, ensuring proper timing and effective therapy delivery.

[0132] Furthermore, according to an aspect of the present invention, the control unit is configured to calculate a crossing point of two straight lines to determine the optimal number of pulses Ni for a therapy sequence. The first line is defined by the rate of change of post-pacing intervals PI between sequential therapy sequences, to be calculated by

[0133] N(PI) = ((PIi+I-PIi) / (Ni+I-Ni))*PI

[0134] and the second line corresponds to a plateau post-pacing interval value Pls, to be calculated by

[0135] 23.162P-WO / 09.03.2026N(PI) = Pls

[0136] whereby

[0137] Ni is the number of pulses of therapy sequence TSi,

[0138] Ni+1 is the number of pulses of the subsequent therapy sequence TSi+1,

[0139] Pli is the time interval measured between the last pulse of the therapy sequence i and a first detected intrinsic cardiac event after the last pulse of the therapy sequence TSi,

[0140] PIi+1 is the time interval measured between the last pulse of a subsequent therapy sequence TSi+1 and a first detected intrinsic cardiac event after the last pulse of the subsequent therapy sequence TSi+1.

[0141] The crossing point between the two straight lines defines Ns, wherein Ns is the number of SI pulses required for the therapy sequence to take control over the reentry. In other words, the abscissa of the crossing point defines the smallest pulse count that yields the maximal post-pacing interval, representing entrainment threshold for the ATP therapy adjustment.

[0142] For example, Ni and Ni+1 are greater than 5.

[0143] The inventive solution enables continuous automated adaptation to patient-specific and temporally variable tachycardia conditions, providing a more agile alternative to existing anti -tachycardia pacing methodologies.

[0144] Definitions

[0145] 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 anti-tachycardia pacing therapy.

[0146] 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.

[0147] The term „electrical pulses" as used herein refers to programmed electrical stimuli delivered via electrode poles to the heart to modify cardiac rhythm during anti-tachycardia pacing therapy.

[0148] 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.

[0149] 23.162P-WO / 09.03.2026The term „electrical pulse" as used herein refers to a single therapeutic electrical stimulus delivered to the heart as part of a therapy sequence.

[0150] 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.

[0151] The term „events" as used herein refers to distinct cardiac electrical occurrences detected in sensed signals, including intrinsic cardiac actions and delivered pulses.

[0152] The term „post-pacing intervals" as used herein refers to time intervals measured from the last delivered electrical pulse of a therapy sequence to the first subsequent intrinsic cardiac event.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] The term „time intervals" as used herein refers to measured durations between detected cardiac electrical events used to assess cardiac rhythm conditions.

[0157] The term „first post-pacing interval PI 1 " as used herein refers to the time measured between the last pulse of the first therapy sequence and the first detected intrinsic cardiac event following that pulse.

[0158] The term „electrical signal" as used herein refers to the cardiac electrical activity recorded by the implantable medical device's sensing electrodes.

[0159] 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.

[0160] 23.162P-WO / 09.03.2026The 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.

[0161] The term „cardiac pacemaker" as used herein refers to a type of implantable medical device that provides electrical pacing to regulate the heart rhythm.

[0162] The term „control unit" as used herein refers to the device component responsible for analyzing detected cardiac events, computing parameters, and adjusting therapy sequences dynamically.

[0163] The term „ICD" as used herein refers to an implantable cardioverter-defibrillator device capable of delivering anti-tachycardia pacing and high-energy shocks to treat arrhythmias.

[0164] 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 tachycardia cycle length.

[0165] The term „second tachycardia condition" as used herein refers to a subsequent detection of tachycardia after delivery of a preceding therapy sequence, triggering further therapy actions.

[0166] 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.

[0167] 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.

[0168] The term „therapy sequence" as used herein refers generally to a group of electrical pulses delivered in succession to interrupt tachycardia.

[0169] The term „first therapy sequence TSI" as used herein refers to the initial sequence of electrical pulses delivered upon detecting the first tachycardia condition.

[0170] The term „electrical signals" as used herein refers to the cardiac electrical activity continuously sensed by the implantable medical device for rhythm analysis.

[0171] 23.162P-WO / 09.03.2026The term „second post-pacing interval PI2" as used herein refers to the time interval measured between the last pulse of the second therapy sequence and the first intrinsic cardiac event detected thereafter.

[0172] 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.

[0173] The term „PI2" as used herein refers synonymously to the second post-pacing interval measured after the second therapy sequence.

[0174] The term „ATP" as used herein refers to anti -tachycardia pacing, a therapy involving electrical pulses to terminate tachycardia by interrupting abnormal cardiac rhythms.

[0175] The term ..parameter" as used herein refers to a quantifiable characteristic or variable used by the control unit to configure or adjust therapy sequences.

[0176] The term „detection unit" as used herein refers to the device component responsible for sensing cardiac electrical events and analyzing them to identify tachycardia conditions.

[0177] 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.

[0178] 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.

[0179] The term „first events" as used herein refers to the plurality of cardiac electrical events detected prior to and triggering the first therapy sequence.

[0180] 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.

[0181] 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.

[0182] 23.162P-WO / 09.03.2026The 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.

[0183] The 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.

[0184] 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 :

[0185] Fig 1 illustrates a schematic view of an implantable medical device interacting with a heart.

[0186] Fig. 2 shows a schematic of intrinsic rhythm, tachycardia detection, and delivery of a first ATP therapy sequence.

[0187] Fig 3 illustrates a schematic view of pulse intervals and intrinsic cardiac events for anti-tachycardia pacing according to embodiments of the invention.

[0188] Fig 4 illustrates a schematic view of a simulation of therapy sequences with increasing pulse count.

[0189] Fig. 5 illustrates an algorithmic approach for adapting therapy sequences based on PI trends.

[0190] Fig 1 shows the implantable medical device 100 connected to a heart 110 via electrode poles 111. The device consists of a stimulation unit 120, detection unit 130, control unit 140 and memory unit 150. These components are enclosed within the 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

[0191] 23.162P-WO / 09.03.2026and 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. Fig 1 shows alternative configurations whereby 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.

[0192] 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 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. Successive pulses within the sequence are separated by an intra-sequence pulse interval SISI 230 (e.g., an inter-pulse-interval chosen as a fraction of the preceding tachycardia cycle length). After the last pulse of the therapy sequence 200, the device measures a post-pacing interval PI 240 to the first intrinsic cardiac event 212 that follows this last pulse. 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.

[0193] Figure 3 details the concept of dynamic therapy adjustment using at least two therapy sequences and the comparison of their respective post-pacing intervals PL A first therapy sequence 301 (e.g., TSI) is delivered during a tachycardia state 320 having tachycardia cycle length TCL1 320b that satisfies detection and stability criteria (e.g., within predefined zone limits). The last pulse of the first sequence is denoted 301a. If a tachycardia with specified characteristics persists (depicted as 330, having TCL2 330b and 331 having TCL3 331b and for continued rhythm evaluation around the first sequence), the system measures a first post-pacing interval PI1 311 between the last pulse 301a and the first intrinsic cardiac event 33 Oathat follows. Subsequently, a second therapy sequence 302 (e.g., TS2) is delivered. If the tachycardia persists and meets the criteria after this second sequence (tachycardia state 340, assessed with TCL4340b), a second post-pacing interval PI2312 is measured from 302a to the first intrinsic event 340a. Thus, Fig. 3 presents a pair of comparable measurements — PI1 311 and PI2312 — obtained under certain tachycardia conditions (before and after a plurality of therapy sequence TSi. A relation parameter RP1 (not depicted) can be computed from PI1 311 and PI2 312, for example as a difference or other comparison metric. Depending on RP1, the control unit 140 generates parameters for a subsequent therapy sequence (e.g., increasing or decreasing the number

[0194] 23.162P-WO / 09.03.2026of pulses, modifying inter-pulse intervals, and / or adjusting the coupling interval). According to an embodiment, if PI2312 > PI1 311 when the number of pulses of the second sequence is greater than that of the first, the device may select a subsequent sequence with a still higher pulse count. Conversely, if PI decreases or fails to increase beyond a defined minimum tolerance, the device may stop further sequence or lengthen at least one pulse interval of the next sequence.

[0195] Figure 4 presents a simulation that illustrates the evolution of the post-pacing interval as a function of the number of pulses Ni per therapy sequence TSi. The upper diagram shows a succession of sensed cardiac signals, the signals showing sections comprising a tachycardia state 420, followed by a therapy sequence 410 and Post-pacing interval Pli. A tachycardia state reappears after each therapy attempt, and the successive therapy sequences show an increasing number of pulses Ni. An increasing PI is observable with higher number of Ni, until a plateau is reached see e.g., PI3 compared to PI and PI10. The lower diagram aggregates these Pli over the increasing Ni. As Ni rises, the measured PI values increase and eventually reach a saturation region. The value 400 (Ns) denotes the minimum number of SI pulses at which the therapy sequence takes control of the reentry (entrainment) — i.e., the smallest Ni at which further increases no longer yield a relevant increase in PI (within a defined tolerance). Identification of Ns 400 is valuable for parameterizing subsequent therapy sequences: a next sequence may be configured with N = Ns pulses at interval SISI, optionally followed by one or more additional “ramp” pulses with intervals shorter than SISI (subject to minimum permissible interval constraints), or therapy may be adapted in other ways if additional pulses fail to further increase PI. It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teaching. The disclosed examples and embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention. Furthermore, all features and embodiments described for the device according to the invention are applicable to the method.

[0196] Figure 5 illustrates a schematic representation of determining the minimum number of SI pulses at which the therapy sequence takes control of the reentry (entrainment) Ns (see e.g. 400 of Fig. 4) for anti-tachycardia pacing based on post-pacing interval, Pli analysis. The diagram shows a graph where the x-axis represents the number of pulses Ni in successive therapy sequences TSi, and the y-axis represents the corresponding post-pacing intervals Pli measured after each therapy sequence.

[0197] A first straight line 500 passes through the point (NI, PI1) and has a slope sPI 501, calculated by

[0198] 23.162P-WO / 09.03.2026sPI = (PI2 - PI1) / (N2 - Nl),

[0199] where N1 and N2 denote the number of pulses in two successive therapy sequences and PI1, PI2 are their respective post-pacing intervals. A second straight line 510 represents the plateau value Pls, which corresponds to the saturation region of PI values. The intersection of these two lines defines the calculated entrainment threshold Ns, which is the smallest number of pulses required for the therapy sequence to take control of the reentrant circuit.

[0200] 23.162P-WO / 09.03.2026Reference Numeral List

[0201] 100 implantable medical device

[0202] 110 heart

[0203] 111 electrode poles

[0204] 120 stimulation unit

[0205] 130 detection unit

[0206] 140 control unit

[0207] 150 memory unit

[0208] 160 signal communication unit

[0209] 200, 410 therapy sequence

[0210] 209 Cycle Length (CL) of healthy rhythm

[0211] 210, 211 Tachycardia Cycle Lengths (TCL) before and after therapy

[0212] 210b, 21 lb observation windows for TCL measurement

[0213] 212 first intrinsic cardiac event after therapy

[0214] 220 coupling interval (RSI) between last intrinsic event and first therapy pulse

[0215] 230 Inter-pulse-interval (IPI, SISI) within the therapy sequence

[0216] 240 Post-Pacing Interval (PI) after last pulse of therapy

[0217] 301, 302 first and second therapy sequences TS1, TS2

[0218] 301a, 302a last pulse of respective therapy sequences

[0219] 311, 312 Post-Pacing Intervals PI1 and PI2

[0220] 320, 330, 331, 340 tachycardia states before and after therapy attempts

[0221] 320b, 330b, 331b, 340b Tachycardia Cycle Lengths TCL before and after therapy attempts 330a, 340a first intrinsic cardiac events after therapy sequence

[0222] 400 Ns, minimum number of SI pulses at which the therapy sequence takes control of the reentry (entrainment)

[0223] 420 tachycardia state

[0224] 500 first straight line

[0225] 501 slope sPI

[0226] 510 second straight line

[0227] 23.162P-WO / 09.03.2026

Claims

Claims1. Implantable medical device (IMD, 100) for anti -tachycardia pacing (ATP) of a heart (110), comprising:- at least one 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 TSi (200) to the heart (110), wherein i is an index number, and wherein 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 at least one therapy sequence TSi (200), and- derive at least one parameter to adjust the therapy sequence TSi (200) based on the events, characterized in thatthe stimulation unit (120) is configured to deliver a first therapy sequence TSI (301) comprising at least one electrical pulse to the heart (110) if the detection unit (130) detects a first tachycardia condition based on a plurality of first events,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 TSI (301), the detection unit (130) is configured to measure a first post-pacing interval PI 1 (311) between the last pulse (301a) of the first therapy sequence TSI (301) and a first detected intrinsic cardiac event (330a, 340a) after the last pulse (301a) of the first therapy sequence TSI (301),wherein the stimulation unit (120) is configured to deliver a second therapy sequence TS2 (302) to the heart (110),wherein, 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 (302), the detection unit (130) is configured to measure at least one second post-pacing interval PI2 (312) between the last pulse (302a) of the second therapy sequence TS2 (302) and a first detected intrinsic cardiac event after the last pulse (302a) of the second therapy sequence TS2 (302),wherein the control unit ( 140) is configured to compute a first relation parameter RP 1 between PI1 (311) and PI2 (312),and wherein the control unit (140) is configured to generate a third therapy sequence TS3 depending on the first relation parameter RP 1.23.162P-WO / 09.03.20262. IMD (100) 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 (100) according to claim 1 or 2, wherein the control unit (140) is configured to generate an inter-pulse-interval IPIi (230)- between at least two of a plurality of electrical pulses of a therapy sequence if the therapy sequence TSi (200) 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 (200) comprises one pulse,wherein the inter-pulse-interval IPIi (230) is shorter than the tachycardia cycle length TCL of the preceding events.

4. IMD (100) 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 (240).

5. IMD (100) according to at least one of the preceding claims, wherein the control unit (140) is configured to generate at least one therapy sequence TSi (200) by adjusting at least one of the following parameters:- a duration of the therapy sequence,- a number of pulses Ni of a therapy sequence,an inter-pulse-interval IPIi (230) between at least two pulses of a therapy sequence, - a coupling interval RSi (220) between a last pulse of the events having a tachycardia condition and the first pulse of a therapy sequence.

6. IMD (100) according to claim 4 and 2, wherein- the coupling interval RSi (220) is computed by rs*TCL, whereby 0.5 < rs < 1;- the inter-pulse-interval IPIi (230) is computed by ipi*TCL, whereby ipi < rs,- whereby all inter-pulse-intervals of a therapy sequence are of equal length.

7. IMD (100) according to the claims 5 or 6, wherein ifNi >Ni-l, and Pli > Pli- 1,23.162P-WO / 09.03.2026the control unit (140) is configured to adjust at least one subsequent therapy sequence by Ni+1 >Ni,wherein- Ni-1 = number of pulses of a preceding therapy sequence,- Ni+1 = number of pulses of a subsequent therapy sequence,- Pli (240) = post-pacing interval between the last pulse (301a, 302a) of the therapy sequence and a first detected intrinsic cardiac event (330a, 340a) after the last pulse of the therapy sequence,- PIi-1 = post-pacing interval between the last pulse (301a, 302a) of the preceding therapy sequence and a first detected intrinsic cardiac event (330a, 340a) after the last pulse of the preceding therapy sequence.

8. IMD (100) according to at least one of the preceding claims, wherein the control unit (140) is configured to apply no further therapy sequence if Pli < Pli- 1.

9. IMD (100) according to at least one of the claims 5 to 8, wherein the control unit (140) is configured to store in a memory unit (150) 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 postpacing interval Pls between the last pulse of the therapy sequence TSs and a first detected intrinsic cardiac event (330a, 340a) after the last pulse of the therapy sequence out of a number n of post-pacing intervals.

10. IMD (100) according to at least one of the claims 5 to 9, wherein the at least one therapy sequence TSi (200) comprises a number of pulses Ni having a first inter-pulse-interval IPIi (230), 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 (230).

11. IMD (100) according to claim 10 and claim 9, wherein Ni is equal to Ns.

12. IMD (100) according to at least one of the claims 4 to 11, wherein ifNi > Ni-1, and Pli < Pli- 1,wherein- Ni = number of pulses of a therapy sequence,- Ni-1 = number of pulses of a preceding therapy sequence,23.162P-WO / 09.03.2026- Pli (240) = post-pacing interval between the last pulse of the therapy sequence and a first detected intrinsic cardiac event (330a, 340a) after the last pulse of the therapy sequence, - Pli- 1 = post-pacing interval between the last pulse of the preceding therapy sequence and a first detected intrinsic cardiac event (330a, 340a) after the last pulse of the preceding therapy sequence,the control unit (140) is configured to generate a subsequent therapy sequence TSi+1 by IPIi +1 > IPIi,wherein- IPIi +1 = at least one inter-pulse-interval between at least two pulses of TSi+1IPIi = at least one inter-pulse-interval between at least two pulses of TSi.

13. 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.

14. 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 TS 1 (301) comprising at least one electrical pulse to the heart (HO),- if a second tachycardia condition is detected based on a plurality of second events after delivery of the first therapy sequence TSI (301), measure a first post-pacing interval PI1 (311) between the last pulse of the first therapy sequence TSI (301) and a first detected intrinsic cardiac event (330a, 340a) after the last pulse of the first therapy sequence TSI (301), - deliver a second therapy sequence TS2 (302) to the heart (110),- if a third tachycardia condition is detected based on a plurality of third events after delivery of the second therapy sequence TS2 (302), measure a second post-pacing interval PI2 (312) between the last pulse of the second therapy sequence TS2 (302) and a first detected intrinsic cardiac event (330a, 340a) after the last pulse of the second therapy sequence TS2 (302), - compute a first relation parameter RP1 between PI1 (311) and PI2 (312),- generate a third therapy sequence TS3 depending on the first relation parameter RP1.

15. Method according to claim 14, wherein the relation parameter is a difference D between two successively measured post-pacing intervals Pli (240).23.162P-WO / 09.03.2026

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