Anti-tachycardia pacing implantable medical device

Abstract

An implantable medical device for anti-tachycardia pacing of a heart is disclosed that includes at least a first pair and a second pair of electrode poles. The electrode poles are configured to sense electrical signals of the heart and / or to apply electrical pulses to the heart. The implantable medical device further includes a stimulation unit configured to deliver electrical pulses to the heart via at least one pair of electrode poles of the first and second pair of electrode poles. The stimulation unit is configured to deliver at least one therapy sequence to the heart. The therapy sequence includes at least one electrical pulse. The implantable medical device further includes a detection unit configured to detect the sensed electrical signals. The detection unit is configured to detect events in the sensed electrical signals. The detection unit is configured to analyze time intervals between the events. The detection unit is configured to detect a tachycardia condition based on the events. The implantable medical device further includes a control unit configured to generate at least one therapy sequence. The control unit is configured to derive at least one parameter based on the events. If the detection unit detects a first tachycardia condition based on a plurality of first events, the stimulation unit delivers a first therapy sequence including at least one electrical pulse to the heart. The first therapy sequence is delivered via at least one pair of electrode poles of the first and second pair of electrode poles. The control unit selects whether the first therapy sequence is delivered via the first pair of electrode poles or via the second pair of electrode poles. The first pair of electrode poles is configured to stimulate at least a part of the conduction system of the heart that includes at least one of a Bachmann bundle, an AV node, a His Bundle, a left bundle branch, a right bundle branch, and Purkinje fibers of the heart.

Description

[0001] Anmelder: BIOTRONIK SE & Co. KG

[0002] Datum: 13.03.2026

[0003] Unser Zeichen: 23.177P-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 medical devices (IMDs) for cardiac rhythm management may be configured to sense intrinsic cardiac electrical activity and to deliver electrical stimulation therapy. Such IMDs may include, by way of example, cardiac pacemakers, implantable cardioverter-defibrillators (ICDs), cardiac re synchronization therapy (CRT) devices, and conduction system pacing (CSP) devices. In certain clinical scenarios, an IMD may deliver anti-tachycardia pacing (ATP) therapy to terminate or mitigate tachyarrhythmias by applying one or more therapy sequences including one or more electrical pulses.

[0007] To support ATP delivery, an IMD may include a detection function configured to detect sensed electrical signals, identify events in the sensed electrical signals, analyze time intervals between events, and detect a tachycardia condition based on the events. Upon detection of a tachycardia condition, a stimulation function may deliver a therapy sequence.

[0008] Conduction system pacing (CSP) uses IMDs to stimulate the heart’s native electrical pathways, including the His Bundle, the left bundle branch, and — more recently explored — the atrial conduction system. By pacing these physiological structures, CSP preserves the heart’s natural activation sequence rather than producing the dyssynchronous contraction often seen with conventional right- ventricular pacing. Ventricular CSP maintains coordinated ventricular contraction, improves hemodynamic efficiency, and reduces the risk of pacing-induced cardiomyopathy. Atrial CSP, which targets areas such as the Bachmann bundle region, aims to restore or preserve synchronized atrial activation, potentially reducing atrial desynchrony and the likelihood of atrial arrhythmias, including atrial fibrillation. In patients with conduction disease such as left bundle branch block, left bundle branch area pacing can re-establish near-normal ventricular activation, offering clinical benefits comparable to cardiac resynchronization therapy and serving as an alternative when coronary sinus lead placement is difficult.In particular, there is a need for new approaches to reduce the number of unsuccessful ATP attempts, enhance the chances of tachycardia termination, and minimize the need for high-energy shocks.

[0009] The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosed subject matter. This summary is not an extensive overview, and it is not intended to identify key / critical elements or to delineate the scope thereof. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

[0010] According to the present invention, an implantable medical device for anti-tachycardia pacing of a heart is disclosed that includes at least a first pair and a second pair of electrode poles. The electrode poles are configured to sense electrical signals of the heart and / or to apply electrical pulses to the heart. The implantable medical device further includes a stimulation unit configured to deliver electrical pulses to the heart via at least one pair of electrode poles of the first and second pair of electrode poles. The stimulation unit is configured to deliver at least one therapy sequence to the heart. The therapy sequence includes at least one electrical pulse. The implantable medical device further includes a detection unit configured to detect the sensed electrical signals. The detection unit is configured to detect events in the sensed electrical signals. The detection unit is configured to analyze time intervals between the events. The detection unit is configured to detect a tachycardia condition based on the events. The implantable medical device further includes a control unit configured to generate at least one therapy sequence. The control unit is configured to derive at least one parameter based on the events. If the detection unit detects a first tachycardia condition based on a plurality of first events, the stimulation unit delivers a first therapy sequence including at least one electrical pulse to the heart. The first therapy sequence is delivered via at least one pair of electrode poles of the first and second pair of electrode poles. The control unit selects whether the first therapy sequence is delivered via the first pair of electrode poles or via the second pair of electrode poles. The first pair of electrode poles is configured to stimulate at least a part of the conduction system of the heart that includes at least one of a Bachmann bundle, an AV node, a His Bundle, a left bundle branch, a right bundle branch, and Purkinje fibers of the heart.

[0011] The IMD according to the invention allows delivering the ATP therapy sequence using a selectable pacing site, including an electrode pair that is capable of CSP, which may support adapting ATP delivery to a detected tachycardia condition.

[0012] 23.177P-WO / / 13.03.2026In 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

[0013] - The time intervals between the events fulfill at least one stability parameter.

[0014] 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.

[0015] In an embodiment, the implantable device is configured to determine stability parameters such as a difference between a predetermined number of preceding tachycardia cycle lengths and a stability threshold value, a standard deviation, a dominant frequency derived from frequency analysis, or autocorrelation-based parameters to assess the stability consistency of tachycardia events before confirming a tachycardia condition.

[0016] 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:

[0017] 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.

[0018] Ventricular Fibrillation (VF) zone 3 is defined as tachycardias equal to or greater than 222bpm.

[0019] In some aspects of the implantable medical device, the detection unit detects events in the sensed electrical signals via one pair of electrode poles of the first and second electrode poles during and / or after delivery of the first therapy sequence. The control unit generates at least a first parameter based on the events detected during and / or after delivery of the first therapy sequence. The first parameter is associated with an effect on the heart caused by the first therapy sequence. The control unit adjusts the first therapy sequence based on the first parameter and / or generates at least one second therapy sequence based on the first parameter.

[0020] According to an embodiment of the present invention, the control unit adjusts the first therapy sequence dynamically during delivery of the therapy sequence. Alternatively, the control unit is configured to generate at least one second therapy sequence based on the first parameter, wherein the second therapy sequence is delivered after the first therapy sequence.

[0021] 23.177P-WO / / 13.03.2026Utilizing parameters detected during and / or after an initial ATP attempt to optimize the configuration of the ongoing ATP sequence has the potential to increase the likelihood of tachycardia termination.

[0022] In some aspects of the implantable medical device, the control unit delivers the first therapy sequence via the first pair of electrodes in a first mode and in a second mode. The first mode includes at least one stimulation parameter for stimulation of at least a part of a conduction system. The second mode includes at least one stimulation parameter for stimulation of a myocardium. The first mode includes at least one of an amplitude, a pulse width, an amount of electrical charge, and a pulse shape of at least one electrical pulse that is different from at least one of an amplitude, a pulse width, an amount of electrical charge, and a pulse shape of at least one electrical pulse of the second mode.

[0023] According to an embodiment, at least one of the amplitude, the pulse width, and the amount of electrical charge of the first mode is larger than at least one of the amplitude, the pulse width, and the amount of electrical charge of the second mode.

[0024] According to an exemplary embodiment, the detection unit analyzes at least one characteristic in the events detected during and / or after delivery of the first therapy sequence. The at least one characteristic includes at least one of the following: a pattern in a plurality of time intervals between intrinsic cardiac activities and / or paced pulses caused by the first therapy sequence, a morphology of at least one event of the events detected during delivery of the first therapy sequence, crossing of a predefined threshold, extrema, maximum slope, or curvature. The control unit generates the at least one first parameter based on the at least one characteristic. This can support robust derivation of the first parameter and facilitate discrimination of therapy effects and selection of a subsequent therapy sequence.

[0025] Preferably, the second pair of electrode poles is configured to stimulate the right ventricle of the heart or the left ventricle of the heart.

[0026] According to an aspect of the present invention, the control unit adjusts the first therapy sequence and / or generates the second therapy sequence based on the first parameter by adjusting at least one of the following parameters: a duration of the first and / or second therapy sequence, a number of pulse series of the first and / or second therapy sequence, a number of pulses of the first and / or second therapy sequence, an inter-pulse interval between at least two pulses of the first and / or second therapy sequence, and a coupling interval between a last pulse of the events having a tachycardia condition and the first pulse of the first and / or second therapy sequence.

[0027] 23.177P-WO / / 13.03.2026In some aspects of the implantable medical device, the detection unit detects second events in the sensed electrical signals via the first and the second pair of electrode poles as an effect on the heart caused by delivery of at least one first electrical pulse. The detection unit further detects a delay time between delivery of the at least one first electrical pulse and sensing of the second events at each pair of electrode poles. The control unit determines the pair of electrode poles having the longest delay time as a preferred pair of electrode poles for detecting events in the sensed electrical signals.

[0028] For example, the at least one first electrical pulse is part of the first therapy sequence, and / or is delivered by the stimulation unit when no tachycardia condition has been detected by the detection unit. This can increase the reliability in selecting a suitable sensing pair of electrode poles.

[0029] According to an embodiment of the present invention, the control unit switches between pairs of electrode poles for delivering electrical pulses and / or switches between pairs of electrode poles for detecting the sensed electrical signals.

[0030] In some aspects of the implantable medical device, the stimulation unit delivers at least one therapy sequence via each pair of electrode poles. The detection unit detects an effect of each of the therapy sequences. The control unit selects the pair of electrode poles for further application of electrical pulses to the heart that showed a best effect. The best effect is reached if the detection unit detects an entrainment condition using a therapy sequence having a smaller number of electrical pulses, and / or if a therapy sequence has a smaller time difference (for example, difference D) between delivery of the therapy sequence and detection of the entrainment condition. An entrainment condition is detected if at least one therapy sequence succeeded in capturing the heart.

[0031] Entrainment is the process of capturing and “over-driving” a reentrant tachycardia circuit by pacing slightly faster than the tachycardia cycle length. When the pacing rate is just faster than the ongoing ventricular tachycardia (VT), each paced beat enters the circuit’s excitable gap, drives the circuit at the pacing rate, and can ultimately terminate the tachycardia — typically by causing the paced wavefronts to collide and extinguish within the circuit.

[0032] In some aspects of the implantable medical device, the entrainment condition is detected if the detection unit detects a post-pacing interval between a last pulse of a previous therapy sequence and a first detected intrinsic cardiac event after the last pulse of the previous therapy sequence, and the length of the post-pacing interval exceeds an entrainment threshold. Additionally and / or

[0033] 23.177P-WO / / 13.03.2026alternatively, the entrainment condition is detected if the control unit controls timing of at least one therapy sequence based on at least one propagation time . The propagation time is a time span between delivery of at least one first electrical pulse until arrival of the first electrical pulse at a target area of the heart. The control unit determines the propagation time based on at least one signal parameter from the sensed electrical signals. Additionally and / or alternatively, the entrainment condition is detected via an additional electrode pole. The first electrode pole is located on a first electrode lead. The second electrode pole is located on a second electrode lead.

[0034] According to an embodiment, the propagation time PT is defined as a time span between the delivery of at least one first electrical pulse and the arrival of the electrical pulse at a target area of the heart. For assessing PT, the detection unit of the IMD is configured to detect events in sensed electrical signals and analyses time intervals between the events. The detection unit is configured to extract at least one signal parameter SP from the sensed electrical signals prior to delivering the first electrical pulse and / or during a specific operation mode. The signal parameter SP comprises at least one of a runtime between two events measured in the electrical signals, wherein a first event is measured via a first electrode pole and a second event is measured via a second electrode pole. The control unit determines a QRS width in the electrical signals, a distance between extrema in the electrical signals, and / or an area under a curve.

[0035] According to an embodiment, the control unit determines the propagation time PT based on the at least one signal parameter SP, including by generating a weighted sum comprising a plurality of weights.

[0036] Alternatively or in combination, the control unit is configured to determine a QRS width and / or an RV-LV delay that indicates a time delay between a right ventricular depolarization and a left ventricular depolarization in the sensed electrical signals. PT can be determined using the RV-LV delay and / or by PT = QRS width * x, wherein x is a correction factor for the measurement inaccuracy of QRS width.

[0037] In some aspects of the implantable medical device, the detection unit detects at least one post-pacing interval between the last pulse of the first therapy sequence and a first detected intrinsic cardiac event after the last pulse of the first therapy sequence. The control unit generates the first parameter based on the at least one post-pacing interval. Advantageously, generating an effect-associated parameter from a post-pacing interval may support evaluating a therapy sequence using a timing -based reaction of the heart.

[0038] 23.177P-WO / / 13.03.2026In some aspects of the implantable medical device, the detection unit detects a first post-pacing interval between the last pulse of the first therapy sequence and a first detected intrinsic cardiac event after the last pulse of the first therapy sequence. The detection unit further detects a second postpacing interval between the last pulse of a second therapy sequence and a first detected intrinsic cardiac event after the last pulse of the second therapy sequence. The control unit generates at least the first parameter based on a difference between the first post-pacing interval and the second postpacing interval.

[0039] According to an embodiment, the control unit is configured to generate a second parameter based on the second post-pacing interval, and wherein the control unit is configured to generate a third therapy sequence based on the first parameter, the second parameter and / or a first relation parameter that is based on the first parameter and the second parameter.

[0040] Based on the first relation parameter, the control unit is configured to generate a third therapy sequence.

[0041] In some aspects of the implantable medical device, the detection unit detects a second tachycardia condition based on a plurality of second events in the sensed electrical signals after delivery of the first therapy sequence. The detection unit determines a phase offset between the first events and the second events. The control unit generates at least the first parameter based on the phase offset.

[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 a first tachycardia cycle length TCL. The offset is then computed as the temporal deviation between one estimated event and its nearest

[0045] 23.177P-WO / / 13.03.2026subsequent second event, normalized to the first TCL. 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.

[0048] 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.

[0049] According to an embodiment of the present invention, the phase offset PS is determined by an angle calculated by

[0050] PS = OTI / TCL1 * 2*Pi

[0051] or

[0052] PS = ((l-OTIj / TCLl) * 2*Pi

[0053] whereby OTI is the offset time interval.

[0054] 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.

[0055] In an embodiment of the invention,

[0056] - the coupling interval RSi is computed by rs*TCL, whereby 0.5 < rs < 1;

[0057] - the inter-pulse-interval IPIi is computed by ipi*TCL, whereby ipi < rs,

[0058] - whereby all inter-pulse-intervals of a therapy sequence are of equal length.

[0059] 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.

[0060] 23.177P-WO / / 13.03.2026According 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 pf 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.

[0061] In 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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

[0066] 23.177P-WO / / 13.03.2026of 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.

[0067] Retaining the minimal effective pulse count that maximizes post-pacing interval allows the device to optimize therapy efficiency, reducing unnecessary stimulation while maintaining efficacy.

[0068] According to an embodiment, Ns is the number of SI pulses required for the therapy sequence to take control over the reentry — e.g. if entrainment is achieved.

[0069] If entrainment is detected, this fact is reported along with the corresponding therapy sequence parameters, for example:

[0070] - to the control unit, which takes this into account when configuring subsequent therapy sequences, - made available to external entities,

[0071] - stored for later processing or retrieval.

[0072] In particular, the value Ns is made available for further processing.

[0073] In an embodiment, the control unit confirms an entrainment 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.

[0074] In some aspects of the implantable medical device, the control unit generates at least one backup therapy sequence. The stimulation unit delivers the backup therapy sequence via the pair of electrode poles that is not used for delivering the first therapy sequence.

[0075] According to an embodiment, the stimulation unit delivers the backup therapy sequence if the detection unit detects a necessity for a backup therapy.

[0076] In an exemplary embodiment, the implantable medical device is a cardiac pacemaker, an implantable cardioverter-defibrillator, or a cardiac rhythm management therapy device.

[0077] Furthermore, a method for operating an IMD for stimulating a human or animal heart is disclosed. The method includes detecting a first tachycardia condition based on a plurality of first events in an electrical signal of the heart. The method further includes selecting whether a first therapy sequence including at least one electrical pulse is delivered to the heart via a first pair of electrode poles or via

[0078] 23.177P-WO / / 13.03.2026a second pair of electrode poles. The first pair of electrode poles is configured to stimulate at least a part of the conduction system of the heart that includes at least one of a Bachmann bundle, an AV node, a His Bundle, a left bundle branch, a right bundle branch, and Purkinje fibers of the heart.

[0079] According to an embodiment, the present invention and embodiments thereof are applicable in transvenous or non-transvenous implantable cardioverter-defibrillators (ICDs), and in both permanent or temporary devices offering ATP therapy options.

[0080] In some aspects, at least one electrode pole is at least a part of a housing of the IMD configured to detect electrical signals from a left or a right ventricle of the heart.

[0081] According to an aspect, the IMD according to the invention is configured for left bundle branch CRT delivery.

[0082] 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.

[0083] Preferably, the detection unit is configured to identify cardiac events with characteristic timing points based on threshold crossings or morphological features, and wherein the tachycardia detection unit is configured to 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 post-pacing interval measurements should be undertaken. Differences between successive post-pacing interval measurements are evaluated using adjustable thresholds to inform subsequent therapy adjustments, including modification of therapy sequence parameters, decisions on continuation of further ATP attempts, or switching to alternative therapies.

[0084] 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.

[0085] 23.177P-WO / / 13.03.2026The 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.

[0086] According to an embodiment, post-pacing intervals, relation parameters, phase offset values, tachycardia characteristics, information on the first or second mode, and other therapy parameters can be stored in the memory unit, read out via a programmer device, and transmitted remotely for further evaluation.

[0087] According to an aspect of the invention, assessments of the post-pacing intervals, relation parameters, phase offset, the first or second mode, and the derivation of therapy parameters may alternatively or additionally be performed by an external instance such as the programmer system or a web / app-based platform, automatically or by trained clinical staff.

[0088] 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.

[0089] Features that are described in the context of separate aspects and embodiments of the invention may be used together and / or be interchangeable. Similarly, features described in the context of a single embodiment may also be provided separately or in any suitable subcombination.

[0090] 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:

[0091] Figs, la-lc schematically illustrate exemplary implantable medical devices according to embodiments of the invention.

[0092] Fig . 2 shows a schematic of intrinsic rhythm, tachycardia detection, and delivery of a first ATP therapy sequence.

[0093] 23.177P-WO / / 13.03.2026Fig. 3 shows an exemplary therapy sequence delivered during a tachycardia episode according to embodiments of the invention.

[0094] Before the present compositions, articles, devices, and / or methods are disclosed and described, it is to be understood that the aspects described below are not limited to specific methods as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

[0095] For purposes of reading the description of the various implementations below, the following descriptions of the sections of the Specification and their respective contents may be helpful:

[0096] Figure la illustrates, in a schematic view, an IMD configured for conduction system pacing (CSP) and anti -tachycardia pacing (ATP) according to embodiments of the invention. An IMD 100 is connected to multiple electrode leads 110, 111 that extend into the heart 120. The first electrode lead 110 is shown positioned such that at least one electrode pole 115a is located in an area suitable for stimulating a portion of the cardiac conduction system, for example in a region adjacent to the septum 130. Electrode lead 111 is located in the right ventricle, with electrode pole 115b configured to deliver right ventricular myocardial stimulation and sensing.

[0097] Figure lb illustrates, in a schematic view, an IMD configured for conduction system pacing (CSP) and anti -tachycardia pacing (ATP) according to embodiments of the invention. An IMD 100 is connected to multiple electrode leads 110, 112 that extend into the heart 120. The first electrode lead 110 is shown positioned such that at least one electrode pole 115a is located in an area suitable for stimulating a portion of the cardiac conduction system, for example in a region adjacent to the septum 130. Electrode lead 112 is located in the coronary sinus, with electrode pole 115c configured to deliver left ventricular myocardial stimulation and sensing.

[0098] Figure 1c illustrates, in a schematic view, an IMD configured for conduction system pacing (CSP) and anti -tachycardia pacing (ATP) according to embodiments of the invention. An IMD 100 is connected to multiple electrode leads 110, 111, and 112 that extend into the heart 120. The first electrode lead 110 is shown positioned such that at least one electrode pole 115a is located in an area suitable for stimulating a portion of the cardiac conduction system, for example in a region adjacent to the septum 130. Electrode leads 111 and 112 extend toward ventricular regions, with electrode lead 111 located in the right ventricle, with electrode pole 115b configured to deliver right ventricular

[0099] 23.177P-WO / / 13.03.2026myocardial stimulation and sensing, and electrode lead 112 located in the coronary sinus, with electrode pole 115c configured to deliver left ventricular myocardial stimulation and sensing.

[0100] Figure 2 shows a time-based schematic of intrinsic rhythm, tachycardia detection, and delivery of a first therapy sequence, along with the timing quantities used for algorithmic control. A baseline healthy rhythm exhibits a cycle length CL 209. A ventricular tachycardia (VT) then occurs with a tachycardia cycle length TCL 210, which is assessed within an observation window 210b to confirm onset and stability of the arrhythmia. Upon detection of a qualifying tachycardia, the implantable medical device delivers a therapy sequence 200 (a first therapy sequence TSi), which is coupled to the last detected intrinsic event via a coupling interval RSI 220 (e.g., chosen as a fraction of the preceding TCL 210). Successive pulses within the therapy sequence are separated by an intra-therapy sequence pulse interval SISI 230 (e.g., an inter-pulse-interval chosen as a fraction of the preceding TCL 210). This phase of equidistant pulse intervals of the therapy sequence is called the burst phase. Optionally, at least one last pulse of therapy sequence 200 can be separated by an inter-pulse interval 231 that is shorter than SISI 230. This phase of at least one shorter pulse interval at the end of a therapy sequence is called the ramp phase. If the therapy attempt is not yet successful, the tachycardia persists with a tachycardia cycle length TCL 211, which is again verified within a corresponding observation window 211b.

[0101] 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.

[0102] 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 programmed tachycardia zone threshold.

[0103] 23.177P-WO / / 13.03.2026Figure 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 tachycardia 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.

[0104] 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 are denoted 230 (SISI) and remain constant across the burst. According to one implementation, the results are computed based on TCLm and a programmable S 1 coupling factor. 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 (S 1 S2 / 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.

[0105] 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).

[0106] 23.177P-WO / / 13.03.2026After 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.

[0107] DEFINITIONS

[0108] The term „Implantable medical device (IMD)“ as used herein refers to an implantable medical device configured for sensing cardiac electrical signals and delivering electrical pulses to the heart, including devices capable of anti-tachycardia pacing (ATP).

[0109] 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.

[0110] The term „electrode lead“ as used herein refers to a lead connected to the IMD that carries one or more electrode poles and is positionable within cardiovascular structures (e.g., septal region, right ventricle, or coronary sinus) for sensing and / or stimulation.

[0111] The term „electrode pair“ as used herein refers to two electrode poles that are configured together to form a sensing and / or stimulation vector for delivering pulses and / or detecting cardiac signals.

[0112] The term ..stimulation unit“ as used herein refers to an IMD subsystem configured to deliver electrical pulses to the heart via at least one pair of electrode poles, including delivery of at least one therapy sequence.

[0113] The term „detection unit“ as used herein refers to an IMD subsystem configured to detect sensed cardiac electrical signals, identify events in the sensed signals, analyze time intervals between events, and detect a tachycardia condition based on the events.

[0114] The term „control unit“ as used herein refers to an IMD subsystem configured to generate at least one therapy sequence, derive at least one parameter based on detected events, and control selection of electrode pairs and timing for therapy delivery.

[0115] 23.177P-WO / / 13.03.2026The term „therapy sequence“ as used herein refers to one or more electrical pulses delivered by the IMD according to defined timing and amplitude parameters for anti-tachycardia pacing of the heart.

[0116] The term „electrical pulse“ as used herein refers to a stimulation output defined by one or more parameters (e.g., amplitude, pulse width, charge amount, polarity, or pulse shape) delivered by the IMD to cardiac tissue.

[0117] The term „event“ as used herein refers to an identified occurrence in a sensed cardiac signal (intrinsic or paced) used for timing analysis, including detection of cardiac depolarizations and algorithmic landmarks (e.g., threshold crossings, extrema, or maximum slope).

[0118] The term „tachycardia condition“ as used herein refers to a rhythm state detected by the detection unit in which event intervals exhibit a tachycardia cycle length (TCL) shorter than a tachycardia threshold and meeting one or more stability criteria and / or tachycardia zone definitions.

[0119] The term „tachycardia cycle length (TCL)“ as used herein refers to the interval between successive tachycardia events, optionally expressed as a mean or median over at least three events, and usable to normalize therapy timing.

[0120] The term „coupling interval (RS1)“ as used herein refers to the interval between the last detected intrinsic tachycardia event and the first pulse of a therapy sequence, which may be set as a fraction of TCL.

[0121] The term „inter-pulse interval (IPI)“ as used herein refers to the interval between two successive pulses within a therapy sequence, which can be defined as a fraction of TCL and may be constant during a burst phase and shortened during a ramp phase.

[0122] The term „burst phase“ as used herein refers to a portion of a therapy sequence in which a plurality of SI pulses are delivered with equidistant inter-pulse intervals normalized to TCL.

[0123] The term „ramp phase“ as used herein refers to a portion of a therapy sequence, optionally following the burst phase, in which one or more terminal inter-pulse intervals are progressively shortened relative to the preceding interval according to a ramp factor.

[0124] 23.177P-WO / / 13.03.2026The term „post-pacing interval (PI)“ as used herein refers to the interval between the last pulse of a therapy sequence and the first detected intrinsic cardiac event thereafter, used to evaluate therapy effect and entrainment.

[0125] The term „entrainment condition“ as used herein refers to a condition indicating that a therapy sequence has captured and over-driven the tachycardia circuit, which may be evidenced by PI behavior exceeding a threshold and / or by timing control based on propagation time.

[0126] The term ..propagation time (PT)“ as used herein refers to the time span from delivery of a first electrical pulse until the arrival of that pulse at a cardiac target area, which may be determined from one or more signal parameters (e.g., QRS width, RV-LV delay, or runtime between events).

[0127] The term „signal parameter (SP)“ as used herein refers to a parameter extracted from sensed signals (e.g., QRS width, distance between extrema, area under the curve, or inter-lead runtimes) used to estimate propagation time or to characterize rhythm.

[0128] The term „phase offset (PS)“ as used herein refers to a normalized phase measure derived from an offset time interval (OTI) between a virtual continuation of pre -therapy tachycardia at TCL and the timing of post-therapy events, optionally expressed as an angle.

[0129] The term „offset time interval (OTI)“ as used herein refers to the temporal deviation used to compute the phase offset, obtained by comparing estimated event timing from a virtual continuation at TCL to the first subsequent post-therapy event.

[0130] The term ..observation window“ as used herein refers to a predefined interval of time during which sensed events are analyzed to determine onset, stability, redetection, or characterization of tachycardia before and / or after therapy delivery.

[0131] The term ..conduction system“ as used herein refers to the heart’s native electrical pathways, including at least one of the Bachmann bundle, AV node, His bundle, left bundle branch, right bundle branch, and Purkinje fibers.

[0132] The term ..conduction system pacing (CSP)“ as used herein refers to pacing targeted to portions of the cardiac conduction system (e.g., His bundle or left bundle branch area) to preserve or restore physiological activation.

[0133] 23.177P-WO / / 13.03.2026The term „anti-tachycardia pacing (ATP)“ as used herein refers to delivery of one or more therapy sequences of electrical pulses intended to terminate or mitigate tachyarrhythmias by entraining and interrupting the re-entrant circuit.

[0134] The term „mode (first mode / second mode)“ as used herein refers to distinct stimulation parameter sets for the same electrode pair, wherein a first mode is configured for stimulation of at least a part of the conduction system and a second mode is configured for stimulation of myocardium.

[0135] The term „backup therapy sequence“ as used herein refers to a therapy sequence generated by the control unit for delivery via a different electrode pair than that used for the initial sequence when backup therapy is deemed necessary.

[0136] The term „delay time“ as used herein refers to the measured time between delivery of an electrical pulse and sensing of a resulting event at a given electrode pair, which can be used to select a preferred sensing pair.

[0137] 23.177P-WO / / 13.03.2026REFERENCE NUMERALS LIST

[0138] 100 Implantable medical device (IMD)

[0139] 110 - 112 Electrode leads

[0140] 115a - 115c Electrode poles

[0141] 120 Heart

[0142] 130 Septum

[0143] 171 Burst phase

[0144] 172 Ramp phase

[0145] 200 Therapy sequence

[0146] 209 Baseline cycle length (CL)

[0147] 210 Tachycardia cycle length (TCL)

[0148] 210a Pre-therapy observation window

[0149] 210b Observation window for tachycardia onset / stability

[0150] 211 Tachycardia cycle length (TCL) after unsuccessful attempt 211b Observation window for post-attempt tachycardia verification 220 Coupling interval RS 1

[0151] 230 SISI inter-pulse interval (IPI)

[0152] 231 Shortened terminal inter-pulse interval(s)

[0153] 242 Sliding observation window

[0154] 300a Post-therapy observation window

[0155] 301 Pre-therapy tachycardia cycle length representative (TCL1) 310 Post-pacing interval (PI)

[0156] 320 Intermittent interval

[0157] 321 Virtual continuation of pre-therapy tachycardia at TCL1 322 Phase offset relative to virtual continuation at TCL1 350 Additional / context observation window

[0158] 360 First intrinsic cardiac event

[0159] 23.177P-WO / / 13.03.2026

Claims

Claims1. Implantable medical device (IMD 100) for anti -tachycardia pacing (ATP) of a heart (120), comprising:- at least a first pair and a second pair of electrode poles (115a, 115b, 115c) configured to sense electrical signals of the heart (120) and / or to apply electrical pulses to the heart (120),- a stimulation unit, configured to deliver the electrical pulses to the heart (120) via at least one pair of the electrode poles (115a, 115b, 115c) of the first and second pair of electrode poles (115a, 115b, 115c), wherein the stimulation unit is configured to deliver at least one therapy sequence (200) to the heart (120), wherein the therapy sequence (200) comprises at least one electrical pulse,- a detection unit, configured to detect the sensed electrical signals, to detect events in the sensed electrical signals, to analyze time intervals between the events, and to detect a tachycardia condition based on the events,- a control unit, configured to:i. generate at least one therapy sequence (200), andii. derive at least one parameter based on the events,the stimulation unit is configured to deliver a first therapy sequence (200) comprising at least one electrical pulse to the heart (120) if the detection unit detects a first tachycardia condition based on a plurality of first events, wherein the first therapy sequence (200) is delivered via at least one pair of electrode poles (115a, 115b, 115c) of the first and second pair of electrode poles (115a, 115b, 115c),characterized in thatthe control unit is configured to select whether the first therapy sequence (200) is delivered via the first or the second pair of electrode poles (115a, 115b, 115c),wherein the first pair of electrode poles (115a, 115b, 115c) is configured to stimulate at least a part of the conduction system of the heart (120), wherein the conduction system comprises at least one of a Bachmann bundle, an AV node, a His Bundle, a left bundle branch, a right bundle branch, Purkinje fibers of the heart (120).

2. IMD (100) according to claim 1, whereinthe detection unit is configured to detect events in the sensed electrical signals via one pair of electrode poles (115a, 115b, 115c) of the first and second electrode poles (115a, 115b, 115c) during and / or after delivery of the first therapy sequence (200),23.177P-WO / / 13.03.2026wherein the control unit is configured to generate at least a first parameter based on the events detected during and / or after delivery of the first therapy sequence (200), wherein the first parameter is associated with an effect to the heart (120) caused by the first therapy sequence (200), and wherein the control unit is configured to adjust the first therapy sequence (200) based on the at least one first parameter, and / or generate at least one second therapy sequence (200) based on the at least one first parameter.

3. IMD (100) according to claim 1 , wherein the control unit is configured to deliver the first therapy sequence (200) via the first pair of electrodes in a first mode and in a second mode, wherein the first mode comprises at least one stimulation parameter for stimulation of at least a part of a conduction system, and wherein the second mode comprises at least one stimulation parameter for stimulation of a myocardium, andwherein the first mode comprises at least one of an amplitude, a pulse width, an amount of electrical charge and a pulse shape of at least one electrical pulse which is different from at least one of an amplitude, a pulse width, an amount of electrical charge and a pulse shape of at least one electrical pulse of the second mode.

4. IMD (100) according to claim 2 or 3, wherein the detection unit is configured to analyze at least one of the following characteristics in the events detected during and / or after delivery of the first therapy sequence (200):- a pattern in a plurality of time intervals between intrinsic cardiac activities and / or paced pulses caused by the first therapy sequence (200),- a morphology of at least one event of the events detected during delivery of the first therapy sequence (200),- crossing of a predefined threshold,- extrema, maximum slope, or curvature,wherein the control unit is configured to generate the at least one first parameter based on the at least one characteristic.

5. IMD (100) according to at least one of the preceding claims, wherein the second pair of electrode poles (115a, 115b, 115c) is configured to stimulate the right or left ventricle of the heart (120).

6. IMD (100) according to at least one of the claims 2 to 5, wherein the control unit is configured to adjust the first therapy sequence (200) and / or to generate the second therapy sequence (200) based on the at least one first parameter by adjusting at least one of the following parameters:23.177P-WO / / 13.03.2026- a duration of the first and / or second therapy sequence (200),- a number of pulse series of the first and / or second therapy sequence (200),- a number of pulses of the first and / or second therapy sequence (200),- an inter-pulse-interval between at least two pulses of the first and / or second therapy sequence (200),- a coupling interval between a last pulse of the events having a tachycardia condition and the first pulse of the first and / or second therapy sequence (200).

7. IMD (100) according to at least one of the preceding claims, wherein the detection unit is configured to- detect second events in the sensed electrical signals via the first and the second pair of electrode poles (115a, 115b, 115c) as effect to the heart (120) caused by the delivery of at least one first electrical pulse, and- detect a delay time between delivery of the at least one first electrical pulse and sensing of the second events at each pair of electrode poles (115a, 115b, 115c),wherein the control unit is configured to determine the pair of electrode poles (115a, 115b, 115c) having the longest delay time as the preferred pair of electrode poles (115a, 115b, 115c) for detecting events in the sensed electrical signals.

8. IMD (100) according to at least one of the preceding claims, wherein the stimulation unit is configured to deliver at least one therapy sequence (200) via each pair of electrode poles (115a, 115b, 115c),and wherein the detection unit is configured to detect an effect of each of the therapy sequences (200), and wherein the control unit is configured to select the pair of electrode poles (115a, 115b, 115c) for further application of electrical pulses to the heart (120) which showed the best effect, wherein the best effect is reached if the detection unit detects an entrainment condition using a therapy sequence (200) having a smaller number of electrical pulses, and / or if a therapy sequence (200) has a smaller time difference between delivery of the therapy sequence (200) and detection of the entrainment condition,wherein an entrainment condition is detected if at least one therapy sequence (200) succeeded in capturing the heart (120).

9. IMD (100) according to claim 8, wherein the entrainment condition is detected- if the detection unit detects a post-pacing interval (310) between a last pulse of a previous therapy sequence (200), and a first detected intrinsic cardiac event after the last pulse of23.177P-WO / / 13.03.2026the previous therapy sequence (200), wherein the length of the post-pacing-interval exceeds an entrainment threshold, and / or- if the control unit is configured to control the timing of at least one therapy sequence (200) based on at least one propagation time, the propagation time being a time span between the delivery of at least one first electrical pulse until arrival of the first electrical pulse at a target area of the heart (120), and wherein the control unit is configured to determine the propagation time based on at least one signal parameter from the sensed electrical signals,and / or- via an additional electrode pole, wherein the first electrode pole is located on a first electrode lead (110,111,112), and the second electrode pole is located on a second electrode lead (110,111,112).

10. IMD (100) according to at least one of the claims 2 to 8, wherein the detection unit is configured to detect at least one post-pacing interval (310) between the last pulse of the first therapy sequence (200) and a first detected intrinsic cardiac event after the last pulse of the first therapy sequence (200), and wherein the control unit is configured to generate the first parameter based on the at least one post-pacing interval (310).

11. IMD (100) according to claim 10, wherein the detection unit is configured to detect- a first post-pacing interval (310) between the last pulse of the first therapy sequence (200) and a first detected intrinsic cardiac event after the last pulse of the first therapy sequence (200), and- a second post-pacing interval (310) between the last pulse of a second therapy sequence (200) and a first detected intrinsic cardiac event after the last pulse of the second therapy sequence (200),wherein the control unit is configured to generate at least the first parameter based on the difference between the first and the second post-pacing interval (310).

12. IMD (100) according to at least one of the claims 2 to 10, wherein the detection unit is configured todetect a second tachycardia condition based on a plurality of second events in the sensed electrical signals after delivery of the first therapy sequence (200),determine a phase offset (322) between the first events and the second events,23.177P-WO / / 13.03.2026and wherein the control unit is configured to generate at least the first parameter based on the phase offset (322).

13. IMD (100) according to at least one of the preceding claims, wherein the control unit is configured to generate at least one backup therapy sequence (200), wherein the stimulation unit is configured to deliver the backup therapy sequence (200) via the pair of electrode poles (115a, 115b, 115c) which is not used for delivering the first therapy sequence (200).

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

15. Method for operating an implantable medical device (IMD (100)) for stimulating a human or animal heart (120), characterized by the following steps:- detect a first tachycardia condition based on a plurality of first events in an electrical signal of the heart (120),- select whether a first therapy sequence (200) comprising at least one electrical pulse is delivered to the heart (120) via a first pair of electrode poles (115a, 115b, 115c) or via a second pair of electrode poles (115a, 115b, 115c),wherein the first pair of electrode poles (115a, 115b, 115c) is configured to stimulate at least a part of the conduction system of the heart (120), wherein the conduction system comprises at least one of a Bachmann bundle, an AV node, a His Bundle, a left bundle branch, a right bundle branch, Purkinje fibers of the heart (120).23.177P-WO / / 13.03.2026

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