Anti-tachycardia pacing implantable medical device

Abstract

An implantable medical device (IMD) for anti-tachycardia pacing ATP of a heart is disclosed. The IMD includes at least three electrode poles configured to sense electrical signals of the heart and / or to apply electrical pulses to the heart. The IMD further includes a stimulation unit configured to deliver the electrical pulses to the heart via at least two of the electrode poles and to deliver at least one therapy sequence to the heart, wherein the therapy sequence comprises at least one electrical pulse. The IMD further includes a detection unit configured to detect the sensed electrical signals, detect events in the sensed electrical signals, analyze time intervals between the events, and detect a tachycardia condition based on the events. The IMD further includes a control unit configured to generate at least one therapy sequence and derive at least one parameter based on the events. In some aspects, if the detection unit detects a first tachycardia condition based on a plurality of first events, the stimulation unit delivers a first therapy sequence comprising at least one electrical pulse to the heart via a first pair of electrode poles selected from the at least three electrode poles. During delivery of the first therapy sequence, the detection unit detects events in the sensed electrical signals via a second pair of electrode poles selected from the at least three electrode poles, wherein at least one electrode pole of the second pair is different from the electrode poles of the first pair. In some aspects, the control unit generates at least a first parameter based on the events detected during delivery of the first therapy sequence, wherein the first parameter is associated with an effect on the heart caused by the first therapy sequence, and the control unit generates at least one second therapy sequence based on the first parameter.

Description

[0001] Anmelder: BIOTRONIK SE & Co. KG

[0002] Datum: 12.03.2026

[0003] Unser Zeichen: 23.164P-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 for anti-tachycardia pacing (ATP) are used to deliver stimulation pulses intended to terminate tachycardia while monitoring cardiac activity to assess rhythm behaviour and therapy outcome. In practice, ATP therapy is often parameterised in advance, and the delivered pulse sequence may proceed without taking account of cardiac responses occurring during therapy delivery. This can lead to delayed convergence toward an effective therapy setting and may require multiple therapy attempts before termination of the tachycardia is achieved.

[0007] 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.

[0008] US Patent 11,134,881 B2 describes a system for detecting an atrial tachyarrhythmia episode that includes a medical device having sensing circuitry configured to receive a cardiac electrical signal from electrodes coupled to the medical device and a processor configured to detect an atrial tachyarrhythmia episode in response to a time duration of the cardiac electrical signal classified as an atrial tachyarrhythmia being greater than or equal to a first detection threshold. The processor is configured to determine if detection threshold adjustment criteria are met based on at least the detected first atrial tachyarrhythmia episode and adjust the first detection threshold to a second detection threshold different than the first detection threshold in response to the detection threshold adjustment criteria being met.

[0009] It is therefore desirable to provide techniques for antitachycardia therapy that enable more reliable assessment of the ongoing effect of delivered pulses on the heart and enable timely adjustment of subsequent therapy based on cardiac activity detected during therapy delivery.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] The following is a non-exhaustive listing of some aspects of the present techniques. These and other aspects are described in the following disclosure. Some aspects include an implantable medical device (IMD) for anti-tachycardia pacing ATP of a heart. The IMD includes at least three electrode poles configured to sense electrical signals of the heart and / or to apply electrical pulses to the heart. The IMD further includes a stimulation unit configured to deliver the electrical pulses to the heart via at least two of the electrode poles and to deliver at least one therapy sequence to the heart, wherein the therapy sequence comprises at least one electrical pulse. The IMD further includes a detection unit configured to detect the sensed electrical signals, detect events in the sensed electrical signals, analyze time intervals between the events, and detect a tachycardia condition based on the events. The IMD further includes a control unit configured to generate at least one therapy sequence and derive at least one parameter based on the events. In some aspects, if the detection unit detects a first tachycardia condition based on a plurality of first events, the stimulation unit delivers a first therapy sequence comprising at least one electrical pulse to the heart via a first pair of electrode poles selected from the at least three electrode poles. During delivery of the first therapy sequence, the detection unit detects events in the sensed electrical signals via a second pair of electrode poles selected from the at least three electrode poles, wherein at least one electrode pole of the second pair is different from the electrode poles of the first pair. In some aspects, the control unit generates at least a first parameter based on the events detected during delivery of the first therapy sequence, wherein the first parameter is associated with an effect on the heart caused by the first therapy sequence, and the control unit generates at least one second therapy sequence based on the first parameter.

[0011] The inventive implantable medical device enables simultaneous therapy delivery and event detection via different electrode-pole pairs, thereby supporting evaluation of cardiac activity during delivery of the first therapy sequence. Advantages can further include deriving the first parameter from events detected during delivery of the first therapy sequence and generating a subsequent therapy sequence based on the first parameter, thereby supporting timely adaptation of therapy in response to an effect on the heart caused by the first therapy sequence.

[0012] 23.164P-WO / / 12.03.2026In some aspects, the detection unit analyzes at least one characteristic in the events detected during delivery of the first therapy sequence, and the control unit generates the at least one first parameter based on the at least one characteristic. The at least one characteristic can include a pattern in a plurality of time intervals during, between or after intrinsic cardiac activities and / or paced pulses caused by the first therapy sequence, a morphology of at least one event of the events, crossing of a predefined threshold, and / or extrema, maximum slope, or curvature.

[0013] This can support robust derivation of the first parameter and facilitate discrimination of therapy effects and selection of a subsequent therapy sequence.

[0014] According to an aspect of the present invention, the electrode poles of the first pair of electrode poles are located on a first electrode lead, and the electrode poles of the second pair of electrode poles are located on a second electrode lead.

[0015] A selection of electrode pole pairs from different leads for respective roles in therapy delivery and event detection enable therapy delivery via a first electrode lead while sensing via a second electrode lead during therapy delivery. Therefore, multi-channel event detection during delivery of the first therapy sequence is supported.

[0016] In some aspects, at least one electrode pole of the first pair of electrode poles has a distance of at least 10 mm to at least one electrode pole of the second pair of electrode poles.

[0017] According to an embodiment of the present invention, the first pair of electrode poles and the second pair of electrode poles are located such that the first pair and the second pair operate in different chambers of the heart.

[0018] Accordingly, a generation of the first parameter based on events detected in a chamber different from the therapy-delivery chamber is enabled.

[0019] In some aspects, the control unit detects second events in the sensed electrical signals via at least two pairs of electrode poles as an effect on the heart caused by delivery of at least one first electrical pulse, and detects, for each of the at least two pairs of electrode poles, a delay time between delivery of the first electrical pulse and sensing of the second events at that pair.

[0020] 23.164P-WO / / 12.03.2026In some aspects, the control unit determines the pair of electrode poles having the longest delay time as the preferred pair of electrode poles for detecting events in the sensed electrical signals.

[0021] 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.

[0022] 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.

[0023] Moreover, in an exemplary embodiment, 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, and the control unit generates the first parameter and / or a second parameter based on the post-pacing interval.

[0024] In some aspects, 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, and detects a second post-pacing 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. In some aspects, the control unit generates the first parameter and / or the second parameter based on a difference between the first post-pacing interval and the second post-pacing interval.

[0025] According to an embodiment, 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.

[0026] Based on the first relation parameter, the control unit is configured to generate a third therapy sequence.

[0027] 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 that is shorter than a tachycardia threshold, and

[0028] • The time intervals between the events fulfill at least one stability parameter.

[0029] 23.164P-WO / / 12.03.2026This approach enhances detection accuracy by incorporating both timing and stability metrics, reducing false positives and ensuring appropriate initiation of therapy only during confirmed tachycardia episodes.

[0030] 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 autocorrelation-based parameters to assess the stability consistency of tachycardia events before confirming a tachycardia condition.

[0031] 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:

[0032] • Ventricular tachycardia (VT) zone 1 is defined as tachycardias equal to or greater than 150bpm.

[0033] • VT zone 2 is defined as tachycardias equal to or greater than 187bpm.

[0034] • VF zone 3 is defined as tachycardias equal to or greater than 222bpm.

[0035] 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.

[0036] Implementing inter-pulse intervals shorter than the tachycardia cycle length improves the likelihood of successfully interrupting tachycardias, thereby enhancing therapy efficacy.

[0037] According to an embodiment of the present invention, the first relation parameter is a difference D between two successively measured post-pacing intervals.

[0038] 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.

[0039] According to an embodiment of the present invention, the detection unit detects a second tachycardia condition based on a plurality of second events in the sensed electrical signals after delivery of the first therapy sequence and determines a phase offset between the first events and the second events.

[0040] 23.164P-WO / / 12.03.2026In some aspects, the control unit generates the first parameter and / or a second parameter based on the phase offset.

[0041] The IMD adapts therapy in real time by measuring the phase offset created by the first therapy sequence and using that information to shape the next, e.g. the second, therapy sequence. This shortens the path to an effective ATP configuration and can reduce repeated ineffective attempts.

[0042] In an embodiment, the control unit generates a second therapy sequence based on the determined phase offset only when the phase offset falls within a specified percentage range of the initial tachycardia cycle length.

[0043] Restricting adaptation to a defined phase window avoids ambiguous timing results and supports consistent decisions. According to an embodiment, a normalized offset is checked whether it lies inside an allowed range before changing therapy parameters.

[0044] In an embodiment, the percentage range used to determine the applicability of phase offset-based therapy adjustment is set between 10% and 90% of the initial TCL.

[0045] In an embodiment, the detection unit determines the phase offset between tachycardia events only when the first tachycardia cycle length, tied to the first tachycardia condition, and a second tachycardia cycle length, tied to the second tachycardia condition, are considered similar, facilitating meaningful comparison and therapy adjustment.

[0046] According to an embodiment, a similar tachycardia cycle length is confirmed if the difference between at least one interval length between two consecutive events of the first events and an interval length between two consecutive events of the second events is smaller than a threshold difference, or if the difference between a mean interval length of the first events and a mean interval length of the second events is smaller than a threshold difference. For example, the threshold difference is 10 ms.

[0047] In an embodiment, the similarity of tachycardia cycle lengths is defined as the difference between the first and second tachycardia cycle lengths being less than or equal to 10 milliseconds for phase offset determination.

[0048] 23.164P-WO / / 12.03.2026In an embodiment, the detection unit calculates the phase offset by virtually extending the timeline of first detected events through estimated events spaced by the initial tachycardia cycle length. The offset is then computed as the temporal deviation between one estimated event and its nearest subsequent second event, normalized to the initial tachycardia cycle length. The temporal deviation is called offset time interval in the following.

[0049] 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.

[0050] 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.

[0051] According to an embodiment of the present invention, the phase offset PS is determined by an angle calculated by

[0052] PS = OTI / TCL1*2* 7i

[0053] or

[0054] PS = (1-OTI / TCL1) * 2*71

[0055] whereby OTI is the offset time interval.

[0056] Furthermore, according to an aspect of the invention, the tachycardia cycle length is a mean or median interval length which is determined across at least 3 events of the first events or the second events.

[0057] In an embodiment, the second therapy sequence includes the same number of electrical pulses as the first therapy sequence, plus one additional pulse. The inter-pulse intervals for the initial pulses are uniform, while the interval between the additional pulse and the last of the initial pulses is shorter if a non-zero phase offset is detected, or equal if the phase offset is zero. Adding one pulse and shortening only the terminal interval when a non-zero offset is present provides a minimal yet targeted change that increases the likelihood of effective interaction. According to an embodiment, the initial ipi is kept constant and the final interval selectively shortened when the measured phase offset indicates a therapeutic benefit.

[0058] 23.164P-WO / / 12.03.2026In an embodiment, the control unit confirms a positive therapeutic effect of the first therapy sequence if the phase offset exceeds a lower threshold or is less than an upper threshold, and stores the corresponding therapy parameters in memory for future reference.

[0059] This positive therapeutic effect is also called "entrainment". Entrainment is the process of capturing and “over-driving” a reentrant tachycardia circuit by pacing slightly faster than the tachycardia cycle length with a sufficient number of pulses. When the pacing rate is just faster than the ongoing ventricular tachycardia (VT), each paced beat enters the circuit’s excitable gap, drives the circuit at the pacing rate, and can ultimately terminate the tachycardia — typically by causing the paced wavefronts to collide and extinguish within the circuit.

[0060] In some aspects, the IMD is configured to perform an entrainment evaluation during delivery of ATP by analyzing a cardiac electrical signal obtained from a sensing vector that is different from the vector which is used for pacing. This enables recognition of when the delivered stimulation pulses have taken over the reentry mechanism (i.e. entrainment is reached), while the therapy sequence is still being delivered, and allows the control unit to adapt a subsequent therapy sequence promptly rather than deferring decisions until after the entire pattern is completed. The embodiment combines morphological assessment and, according to variants, stimulation pulse-to-far-field timing stability, using sensors that are not blanked by pacing.

[0061] Accordingly, the control unit is configured to derive one or more parameters associated with the effect of a first therapy sequence, e.g., an entrainment indicator based on a morphology parameter falling below an entrainment threshold for a specified beat pattern (e.g. based on an X of Y criterion). Optionally, the morphology parameter is evaluated together with a stability criterion of the interval between each ATP stimulation pulse and a ventricular event sensed with a sensing vector — and generates at least one second therapy sequence based on those parameters, in accordance with the present invention and embodiments thereof.

[0062] In some aspects, at least one electrode pole is at least a part of a housing of the IMD and / or at least one electrode pole is located to detect electrical signals from a left ventricle of the heart.

[0063] According to an embodiment, the at least one electrode pole is configured to deliver electrical stimulation within the conduction system of the heart. Conduction system pacing includes e.g. bundle branch pacing as Bachman bundle pacing, left bundle branch area pacing, or His bundle pacing strategies.

[0064] 23.164P-WO / / 12.03.2026In some aspects, the control unit generates the second therapy sequence based on the first parameter by adjusting at least one parameter. The at least one parameter can include a duration of the second therapy sequence, a number of pulses of the second therapy sequence, a pulse width of at least one electrical pulse of the first and / or second therapy sequence, an inter-pulse interval between at least two pulses of the second therapy sequence, and / or a coupling interval between a last pulse of the events having a tachycardia condition and the first pulse of the second therapy sequence.

[0065] According to an embodiment of the present invention,

[0066] • The number of therapy sequences is 10, 20, 30 or 40,

[0067] • The duration of a therapy sequence ranges between 60s to 3600s.

[0068] • The minimum duration between successive therapy sequences is 0.6s.

[0069] According to an aspect of the invention, the control unit is configured to generate at least one of the therapy sequences by adjusting at least one of the following values:

[0070] • a maximum number of therapy sequences,

[0071] • a maximum duration of the therapy sequence,

[0072] • a minimum and / or maximum duration between therapy sequences.

[0073] 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. According to an embodiment, a maximum duration of the therapy sequence is 3600s. Moreover, according to an aspect, the minimum duration is 600ms.

[0074] 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.

[0075] In an embodiment of the invention,

[0076] • the coupling interval is computed by rs*TCL, whereby 0.5 < rs < 1;

[0077] • the inter-pulse-interval is computed by ipi*TCL, whereby ipi < rs,

[0078] • whereby all inter-pulse-intervals of a therapy sequence are of equal length.

[0079] 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.

[0080] 23.164P-WO / / 12.03.2026According to an embodiment of the present invention, the IMD is a cardiac pacemaker, an implantable cardioverter-defibrillator ICD, a cardiac rhythm management therapy CRT device, or a conduction system pacing CSP device.

[0081] Some aspects include a method for operating an implantable medical device IMD for stimulating a human or animal heart. The method can include detecting a first tachycardia condition based on a plurality of first events in an electrical signal of the heart, delivering a first therapy sequence comprising at least one electrical pulse to the heart via a first pair of electrode poles, detecting events in the sensed electrical signals via a second pair of electrode poles during delivery of the first therapy sequence wherein at least one electrode pole of the second pair of electrode poles is different from the electrode poles of the first pair of electrode poles, generating at least a first parameter based on the events detected during delivery of the first therapy sequence wherein the first parameter is associated with an effect on the heart caused by the first therapy sequence, and generating at least one second therapy sequence based on the first parameter.

[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] 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.

[0084] According to an embodiment, the detection unit is configured to analyze cardiac rhythm characteristics, such as cycle lengths, interval stability, dominant frequencies, and periods ascertained from autocorrelation.

[0085] 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.

[0086] 23.164P-WO / / 12.03.2026The 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.

[0087] According to an embodiment, detected or computed parameters, characteristics, values, as e.g. postpacing intervals, phase offsets, tachycardia characteristics, morphology characteristics, entrainment information, and therapy parameters according to embodiments of the invention can be stored in the memory unit, read out via a programmer device, and transmitted remotely for further evaluation.

[0088] According to an aspect of the invention, computation or assessments of the parameters, characteristics, values, as e.g. post-pacing intervals, phase offsets, tachycardia characteristics, and the derivation of therapy parameters according to embodiments of the invention 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.

[0089] In some aspects, the IMD is configured to deliver one or more therapy sequences via a first pair of electrode poles while sensing on a different pair to evaluate cardiac activity during ongoing therapy. The control unit is configured to derive one or more parameters — including entrainment indicators computed from morphological analysis and / or stimulation pulse-to-far-field timing stability — and adapts the subsequent therapy in real time. The analysis can be performed on a beat-to-beat basis.

[0090] According to an embodiment, the morphological analysis may include at least one of the following:

[0091] • QRS complex width

[0092] • Maximum peak-to-peak amplitude (max_Peak2Peak)

[0093] • Number of zero crossings (NZC)

[0094] • Number of zero crossings above a noise band (NZCsqc)

[0095] • Area under the curve (Area)

[0096] • Area under the curve normalized by the max_Peak2Peak value (normArea)

[0097] • Wave difference vector (WDV)

[0098] • Wave difference vector normalized by the max_Peak2Peak value (norm WDV)

[0099] According to a preferred embodiment, a combination of “max_Peak2Peak”, “normArea”, and “norm WDV” is used for the morphological analysis.

[0100] In an embodiment, for determination of a morphological distance, a far-field signal is obtained (for instance from a window of -100 / +150 ms around a trigger on the sensing vector), and features such

[0101] 23.164P-WO / / 12.03.2026as a maximum peak to peak amplitude max_Peak2Peak, a normalized area under the curve normArea, or normalized wave difference vector normWDV are extracted. The morphological distance is computed against a reference (e.g. against a preceding value, a static value or an average value) and tested against thresholds for morphological onset and entrainment.

[0102] According to an aspect, a stimulation-pulse-to-far-field-timing-stability is determined by computing time intervals from a stimulation pulse delivery to a far-field trigger. The stability of such time intervals is observed by comparison with upper and lower threshold values.

[0103] According to an aspect, real time assessment is performed by the IMD of whether ATP has taken over the reentry (entrainment) while the sequence is still in progress. The evaluation is preferably run on a far-field channel that is not blanked by pacing. The algorithm can

[0104] (i) require a morphological onset (signal change above a preset threshold compared to predetection reference or first ATP beat), then

[0105] (ii) confirm entrainment when morphological distance falls below an entrainment threshold for N consecutive beats or X out of Y beats, optionally together with timing stability measures as just described.

[0106] According to an embodiment, a combination of morphology analysis plus timing parameters are used for enhancing the confidence in entrainment detection.

[0107] In an example, electrode poles can include the device housing and may target left ventricular sensing and / or conduction system pacing sites (e.g., His or left bundle branch area).

[0108] According to an embodiment, a first stimulation lead provides a first vector (e.g. for a right ventricular (RV) lead, RV tip-ring vector) for pacing and a second vector (e.g. for an RV-lead, coilcan vector) for far-field sensing. The control unit is configured to execute the beat-wise entrainment evaluation. In an CRT / CSP variant, a left ventricular (LV) lead provides additional options: ATP can be delivered on the LV lead, while far-field triggering and / or morphological evaluation are based on electrical signals obtained via an RV lead coil-can vector, or vice versa. In an example, if a right atrial (RA) lead is present, it may be used for additional functions.

[0109] As an example, values subject to adjustment encompass the number of pulses, inter-pulse intervals, amplitude, polarity, pulse width (for example, also full width at half maximum, in the case of arbitrarily shaped pulses), charge amount, and tilt, in addition to therapy sequence characteristics

[0110] 23.164P-WO / / 12.03.2026such 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.

[0111] 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.

[0112] 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:

[0113] Fig. 1 illustrates a schematic view of an implantable medical device interacting with a heart.

[0114] Fig. 2 shows a schematic of intrinsic rhythm, tachycardia detection, and delivery of a first ATP therapy sequence.

[0115] Fig. 3a shows a timing diagram illustrating delivery of an ATP sequence via a first vector while cardiac events are sensed via a second vector to determine temporal relationships for adapting the therapy sequence.

[0116] Fig . 3b shows a timing diagram illustrating delivery of an ATP sequence via a first vector during a tachycardia while cardiac events are sensed via a second vector and intervals between sensed events are evaluated relative to pacing intervals to dynamically adapt the therapy sequence.

[0117] Fig. 3c shows a timing diagram illustrating evaluation of a monitored interval pattern of cardiac events sensed on a second vector during delivery of an ATP therapy sequence on a first vector to support adaptation of the ATP therapy.

[0118] Fig. 4 depicts a plot illustrating cardiac signals sensed during delivery of an ATP sequence and a corresponding progression of interval values across ATP attempts indicative of entrainment behavior.

[0119] 23.164P-WO / / 12.03.2026Fig. 5 depicts a diagram illustrating delivery of an ATP sequence on a first vector while simultaneously sensing a far-field signal on a second vector, in which a transition from a pre -entrainment tachycardia rhythm to a post-entrainment rhythm is shown.

[0120] Fig. 6 depicts an embodiment of the invention, including a system comprising an IMD and an RV lead, that allows therapy on one vector while sensing on a different, un-blanked vector for entrainment evaluation.

[0121] Fig. 7 shows an extension of Fig. 6 by an LV lead forming a third vector.

[0122] Fig. 8 illustrates a process diagram according to an embodiment of the invention that performs pre-detection-checks followed by VT detection and delivery of an ATP therapy sequence in two phases.

[0123] Fig. 9 depicts an exemplary flowchart of a beat-wise “entrainment” evaluation, that performs morphological-onset classification followed by entrainment classification, whereby an entrainment-sensor state is updated to determine subsequent therapy steps.

[0124] Fig. 10 depicts an overview of selected, morphological features according to embodiments of the present invention.

[0125] Fig. 11 shows an overview of exemplary variants of the beat-based morphological analysis and the morphological comparison.

[0126] Fig. 12 depicts the symbol key used by the subsequent timing diagrams in Figs. 13 - 18.

[0127] Fig. 13 shows an exemplary generation of the signal windows from vector2.

[0128] Fig. 14 shows an exemplary beat-wise morphological entrainment evaluation with a predecessor window.

[0129] Fig. 15 depicts an exemplary beat-wise morphological entrainment evaluation with an averaged reference window.

[0130] 23.164P-WO / / 12.03.2026Fig. 16 shows an exemplary beat-wise morphological entrainment evaluation with predetection and the predecessor window.

[0131] Fig. 17 illustrates an exemplary beat-wise morphological entrainment evaluation with X out of Y criterion for the entrainment recognition.

[0132] Fig. 18 shows an exemplary beat-wise entrainment evaluation from the temporal distance between the stimulation pulse and the signal window trigger.

[0133] 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.

[0134] 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:

[0135] Figure 1 shows the implantable medical device 100 connected to a heart 110 via electrode poles 111. The implantable medical device consists of a stimulation unit 120, detection unit 130, control unit 140 and memory unit 150. These components are enclosed within the implantable medical device housing for device 100. Figure 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. Figure 1 shows the control unit 140 in a closed-loop configuration with the detection unit 130 and stimulation unit 120, allowing dynamic adjustment of therapy sequences based on real-time cardiac event analysis. The memory unit 150 stores parameters such as post-pacing intervals, contributing to therapy sequence adjustments. Figure 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.

[0136] 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

[0137] 23.164P-WO / / 12.03.2026onset and stability of the arrhythmia. Upon detection of a qualifying tachycardia, the implantable medical device delivers a therapy sequence 200 (a first therapy sequence TSi), which is coupled to the last detected intrinsic event via a coupling interval RS 1 220. Successive pulses within the therapy sequence are separated by an intra-therapy sequence pulse interval SISI 230 (e.g., an inter-pulse-interval chosen as a fraction of the preceding TCL). This phase of equidistant pulse intervals of the therapy sequence is called the burst phase. Optionally, at least one last pulse of therapy sequence 200 can be separated by an inter-pulse interval 231 that is shorter than SISI 230. This phase of at least one shorter pulse interval at the end of a therapy sequence is called the ramp phase. If the therapy attempt is not yet successful, the tachycardia persists with a tachycardia cycle length TCL 211, which is again verified within a corresponding observation window 211b.

[0138] 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.

[0139] Figure 3a shows a timing diagram illustrating delivery of a therapy sequence 310 on a first vector 305 during a tachycardia 300 while simultaneously sensing cardiac events on a second vector 306 to derive temporal relationships used for adapting the therapy. The tachycardia 300 is represented by intrinsic cardiac events 302 and 303 occurring with a tachycardia cycle length 301. During delivery of the therapy sequence 310 via the first vector 305, events in the electrical signal are sensed via the second vector 306 and are evaluated to determine temporal relationships 320 between delivered pulses and sensed cardiac activity. Based on the evaluated temporal relationships 320, the therapy may be adapted while the therapy sequence 310 is ongoing, such that originally planned pulses 311, shown as dashed future pulses, are modified in timing and / or number relative to an initial plan.

[0140] 23.164P-WO / / 12.03.2026Figure 3b shows an expansion of the evaluation in Figure 3a. On second vector 306, intervals 340 between the sensed events relative to pacing intervals 330 on first vector 305 are tracked. The control unit is configured to monitor whether intervals shorten relative to tachycardia cycle length 301 using threshold comparisons. Certain changes to the monitored intervals indicate an increasing control by the therapy sequence. Based on such changes, the control unit may dynamically adapt the therapy sequence, aiming to increase the success rate of tachycardia termination.

[0141] Figure 3c shows an expansion of the evaluation in Figure 3a or Figure 3b. On second vector 306, intervals 340 or 341 between the sensed events relative to pacing intervals 330 or 331 on first vector 305 are tracked. If a defined condition is fulfilled (e.g., if a certain pattern is detected that represents a diagnostic condition), the control unit is configured to change parameters of the ongoing therapy sequence, e.g., adjusting remaining count of stimulation pulses, inter-pulse intervals, delivering a terminal S2 pulse, or the like.

[0142] Figure 4 depicts a plot illustrating sensed cardiac signals during delivery of a pulse series 310 and a corresponding progression of interval values indicative of stabilization behavior across attempts. In an upper portion of the plot, intrinsic cardiac events 302 and 303 are shown before and during delivery of the pulse series 310, and a temporal relationship 320 indicates a measured timing relationship between delivered pulses of the pulse series 310 and sensed cardiac events during therapy delivery. In a lower portion of the plot, a curve 400 depicts a progression of post-pacing interval (PI) values across ATP attempts, illustrating that the interval values can change and may exhibit a plateau behavior as attempts progress, indicating entrainment. Entrainment conditions can thus be identified directly from the temporal relationships 320, without having to deliver multiple ATP attempts.

[0143] Figure 5 shows a diagram illustrating delivery of a therapy sequence 310 on a first vector 305, while simultaneously sensing an electrical far-field signal on a second vector 306. The second vector 306 senses an electrical far-field signal (so-called "pseudo-ECG") in which an initial rhythm segment 500 is visible prior to delivering therapy sequence 310. It is apparent that the rhythm 500 of the tachycardia still persists for a while even though the ATP is already in progress. During or after delivery of therapy sequence 310, the sensed electrical signal transitions to a different rhythm segment 510. A further waveform 511 represents a copy of rhythm 510 for comparison to the other two rhythms 500 and that of the therapy sequence 310. The post-entrainment rhythm 510 is stable and slower than the rate of therapy sequence 310, but faster than rhythm 500. Second vector 306

[0144] 23.164P-WO / / 12.03.2026enables observing the entrainment process by using a sensing vector that is not blanked by the pacing pulses.

[0145] Figure 6 schematically shows an overview of the components of the solution according to embodiments of the invention. Embodiments of the algorithm are implemented in the control unit 140. An implantable system 600 comprises IMD 100 and at least one RV electrode 620 having at least three electrode poles 621, 622, 623. The RV electrode 620 is positioned in the right ventricle (RV), or at an implantation site that can be reached via the right ventricle (e.g., left bundle branch area). Electrical signals are derived via

[0146] • vector 1 624, spanned between the electrode poles RV tip 621 and RV ring 622, and via • vector2 625, spanned between the coil 623 and IMD 100, and are routed through an analog / digital (AD) converter as part of AD, filter, offset compensation 611 of the IMD 100.

[0147] In the digitized signal, detection unit 130 generates sense events, which are used in the control unit 140 by the algorithm module and, where necessary, cause the stimulation unit 120 to deliver stimulation pulses. These pulses are transmitted via the electrodes to the ventricular myocardial tissue. Parameterization of the IMD components is carried out by a programming device 700, which exchanges information via the communication unit 701 with the IMD’s communication unit 615. Data can also be sent via communication unit 701 to a remote service center 800.

[0148] Referring to Figure 7. The implantable system 600 of Figure 6 is supplemented by a left ventricular (LV) electrode 630, which is positioned at the left ventricle of the heart and, via vector3633, spanned between the LV tip 631 and LV ring 632 electrode poles, records a corresponding sensing signal and / or can deliver stimulation pulses to the left ventricle.

[0149] Furthermore, Figure 7 takes into account that both sensing and the delivery of stimulation pulses to the left ventricle do not necessarily have to be performed through the same electrode poles. For this purpose, additional LV ring2634 and LV ring3 635 electrode poles are indicated.

[0150] Figure 8 illustrates a process diagram that lists

[0151] • optional pre-detection-checks for morphology stability, RR stability, and signal quality, • followed by VT detection and delivery of an ATP therapy sequence phase 1, while the algorithm evaluates morphological onset and entrainment on a beat-by-beat basis.

[0152] 23.164P-WO / / 12.03.2026Moreover, Figure 8 shows decision points that, upon entrainment recognition, cause the controller to, in a phase 2 of the ATP, deliver part 2 of the therapy sequence (for example, a terminal S2 or ramp, or other types of modification of the therapy sequence) or, if entrainment is not recognized within maximum duration constraints, to continue or fall back to a static pattern, thereby enabling real-time adaptation during the ongoing ATP attempt. Exemplary details of the steps in Figure 8 are listed in the following.

[0153] Pre-detection-phase

[0154] In this phase, a ventricular tachycardia has not yet been recognized

[0155] The TCL (tachycardia cycle length) is ascertained in the form of averaging of the last N RR intervals prior to detection (N preferably 4, range 2-16) (from vectorl)

[0156] For the “Pre-detection-check: morphological stability”, the beat-wise morphological feature extraction and determination of the morphological distance has already been performed (specifically as a ring buffer that always contains the last N morphological beat-to-beat distances, preferably where N=8).

[0157] The “Pre-detection-check: morphological stability” is considered to have been passed when the beat-to-beat ascertained, morphological distance of the last N (preferably 8) events is below a threshold value

[0158] Optionally, the morphology of the last event prior to detection (or the averaged morphology of the last N beats prior to the detection point in time, N preferably 4) is stored as the reference (“reference window preDet”)

[0159] The optional “Pre-detection-check: RR stability” is considered to have been passed when the maximum difference between two of the intervals thus stored is below an absolute limit (for example, 24 ms, range 12-60 ms) or below a relative limit (maximum difference in milliseconds (ms) in relation to the average interval length VTCL) for the interval lengths of the last N beats prior to detection (N preferably 4, range 2-16). Alternatively, only the difference between the last RR interval prior to detection and the 3 immediate predecessors thereof is checked with respect to the RR stability as described above.

[0160] The optional “Pre -detection-check: signal quality” of the lead which is utilized for the morphological signal analysis (far-field, vector2) and is considered to have been passed when a sufficient number of usable beats is present (X out of Y, XooY) in which the amplitude (maxPeak2Peak) is above an SQC (signal quality control)-min threshold (check for very small amplitudes) and below an SQC-max threshold (check for clipping).

[0161] 23.164P-WO / / 12.03.2026ATP therapy sequence, phase 1

[0162] “VT detected?”: From the detection point in time on (ventricular tachycardia is considered to have been recognized in the system), the “ATP therapy sequence, phase 1” is started A respective SI stimulation pulse having a coupling time specifiable by the user is parameterized, based on the (mean) TCL measured prior to detection (e.g. range 50-95%) Optionally, prior conditions can be activated (“Pre-detection-check active?”) - the actual algorithm only becomes active when these (all or individual) prior conditions have been positively passed (“Pre-detection-check requirements met?”; the conditions were already described under the pre-detection phase):

[0163] o “Pre-detection-check: morphological stability“

[0164] o “Pre-detection-check: RR stability“

[0165] o “Pre-detection-check: signal quality“

[0166] If the “Pre-detection-check met?“ is negative, the entrainment evaluation at a minimum appears to be uncertain. Here, alternatively the “Delivery of „static“ therapy sequence pattern” can take place.

[0167] Now, the ATP therapy sequence phase 1 stimulation pulses are delivered (at least 2 since at least 1 is needed for morphological onset (Morph. -Onset in the Figures) and at least one more for identifying the ATP entrainment, as is explained in more detail below): an ATP therapy sequence phase 1 stimulation pulse is temporally delivered based on the predecessor event (pre-detection sense event for the 1st ATP therapy sequence phase 1 stimulation pulse or the preceding ATP stimulation pulse starting with the 2nd stimulation pulse) with selection of a coupling factor that is dependent on TCL (this results in a burst pacing pattern for the overall ATP therapy sequence phase 1).

[0168] The number of delivered ATP therapy sequence phase 1 stimulation pulses is dynamically determined by the algorithm:

[0169] When “ATP entrainment detected?“ has found to be positive, the transition to ATP therapy sequence phase 2 takes place

[0170] Otherwise, the optional check “Maximum duration of phase 1 reached?“ is carried out. This time is a maximum time period to be parameterized by a user which the ATP therapy sequence phase 1 may last. Typically, approximately 10-15 * TCL is to be expected here (that is, for example, ~6s for VTCL = 400 ms). If the maximum time for ATP therapy sequence phase 1 is reached, a transition to ATP therapy sequence phase 2 takes place (optionally also abortion of the ATP attempt as “unsuccessful”).

[0171] As an alternative, the maximum duration for the entire ATP attempt is specified by the user and, taking into consideration the maximum duration of an ATP pattern configured for ATP

[0172] 23.164P-WO / / 12.03.2026therapy sequence phase 2 (and taking the TCL into consideration), the remaining time is used as the maximum duration for the ATP therapy sequence phase 1.

[0173] Otherwise, the next ATP therapy sequence phase 1 stimulation pulse is delivered and accordingly repeated.

[0174] ATP therapy sequence Phase 2

[0175] Here, an ATP pattern is delivered f Delivery of second part of therapy sequence patterrff which is to take over the conditioning of the tissue described at the outset of the (“entrainment”) reentry circuit which was already successfully taken over at this point in time.

[0176] This may be

[0177] o ATP ramp, or, in particular:

[0178] ■ a single S2 pulse

[0179] ■ a pattern of S2, followed by an additional pulse S3 (coupling time of S3 is smaller than coupling time of S2, S1S2 > S2S3)

[0180] ■ a pattern of S2, followed by S3, followed by an additional pulse S4 (coupling time of S4 is smaller than coupling time of S3, S1S2 > S2S3 and S2S3 > S3S4)

[0181] o an alternating sequence of S2 and S 1 (at the ratio of 1 : 1 or 2: 1 or 1 :2, where S2S 1 < S1S2)

[0182] However, this may also be a prepared number of ATP pacing patterns, which are then processed according to a prioritization sequence until a successful pattern has been found.

[0183] Figure 9 depicts an exemplary flowchart of a beat-wise “entrainment” evaluation. To do so, after each ATP stimulation pulse, an optional check of the morphological onset (Morph. -Onset) is performed by determining a current signal difference between a reference signal and the current signal. The current signal difference is compared to an onset threshold. Then, entrainment is evaluated by comparing a morphological distance to an entrainment threshold with possible trend evaluation and X-out-of-Y (XooY) confirmation. Optionally, a trend of the history of the ATP entrainment recognition is evaluated to confirm recognized ATP entrainment. Furthermore, Figure 9 shows the entrainment-sensor state progressing from “inactive” to “onset recognized” and to “entrainment recognized”. The result of controls whether the algorithm continues to ATP therapy sequence phase 1, or transition to phase 2, or alters or terminates the therapy sequence for the ongoing ATP attempt. Exemplary details of the steps in Figure 9 are listed in the following.

[0184] 23.164P-WO / / 12.03.2026“Morph. -Onset”-. Morphological onset. The reason for this check is to avoid false-positive entrainment recognition. This could be the case if the ATP stimulation pulses do not manage to excite heart tissue and, as a result, no noteworthy morphological change can be identified starting with the first ATP stimulation pulse.

[0185] A technical alternative to the morphological onset check could be to perform a stimulation pulse threshold test of the vector which is used for the ATP stimulation pulses. A stimulation pulse threshold test is a standard feature that is typically integrated in IPG and ICD, which in general identifies at regular periodic intervals which stimulation amplitude is necessary to trigger a corresponding reaction in the heart tissue. Such a test is generally used to identify capture, while keeping the stimulation amplitude as low as is necessary to not unnecessarily strain the electricity budget. A positive result of the stimulation pulse threshold test corresponds to a positive morphological onset check.

[0186] A short description of the beat-based morphological analysis can be as follows: Around an event trigger, a signal from the vector to be utilized for the morphological evaluation is windowed. Morphological features are extracted from a current signal window. Then, reference values for the morphological features are determined from one or more signal windows further in the past. Extracted morphological features from a current window are compared against reference values (features from reference window or features from reference morphology or direct reference values) by determining a scalar morphological distance. The morphological features or the morphological distance can be utilized for adapting classification thresholds.

[0187] Figure 10 depicts an overview of selected, morphological features. For instance, a far-field morphology window depicting on a non-paced trigger, typically from vector2 and optionally from vector3, and the extraction of features including max_Peak2Peak, normArea, normWDV, and MaxSlopeTimeDiff are shown. Furthermore, Figure 10 shows how a morphological distance is computed from these features — for example using a combination of max_Peak2Peak, normArea, and normWDV. The computation of the morphological distance enables a detection of the morphological onset and entrainment while pacing is ongoing. Exemplary details of the steps in Figure 10 are listed in the following.

[0188] A: The trigger events for signal windowing stem from a vector2 or vectors . This is not the vector via which the ATP stimulation pulses are delivered since this causes in-channel blanking, whereby the

[0189] 23.164P-WO / / 12.03.2026signal is not available the entire time, and the pacing amplitude during the ATP therapy is typically configured for the maximum amplitude of the system.

[0190] The sampling rate is preferably 128 Hz (64 Hz - 512 Hz). The resolution of the signal is 8 bit (range 4-16 bit).

[0191] Windowing then takes place (e.g. -100 ms before, +150 ms after the trigger event) in vector2 (far-field). The following features are collected on the signal window thus normalized in terms of the length:

[0192] B: "WDVnorm" the normalized wave difference vector results from the wave differences that are divided (normalized) by the max_Peak2Peak amplitude.

[0193] Optionally, wave differences below a threshold value are discarded as “noise signal components”.

[0194] For example, a wave difference results as a difference between second local reversal points in the signal curve having a zero crossing therebetween. The first wave difference results as the first extreme point (sample before the windowing is defined as 0). Likewise, the first sample after the window is defined as zero.

[0195] According to an embodiment, the consecutive N (preferably 4, range 4-16) ascertained wave differences around the wave difference with the maximum value are selected. Alternatively, the first N wave differences are selected.

[0196] C: "max peak21>eak" maximum signal deflection.

[0197] D: “MaxSlopeTimeDiff”'. temporal distance between the zero crossings of the flanks of the wave with maximal wave difference.

[0198] E: "normArea'". the area under the curve is formed as the sum of all amplitudes of the rectified signal. This area value is normalized with the “max_Peak2Peak” value.

[0199] According to an embodiment, the morphological distance is formed by the difference between the features “WDVnorm“, "max PeakkPeak" and "normArea" by forming the sum from the Euclidean distance of "IP / JPnor " of the current window and reference window, as well as the simple difference each of "max Peak2Peak" and “normArea” of the current window and reference window.

[0200] Figure 11 shows an overview of exemplary variants of the beat-based morphological analysis and the morphological comparison, that are detailed in the following:

[0201] 23.164P-WO / / 12.03.2026• The “signal window triggering” for the morphological signal evaluation can be carried out utilizing different leads. For a one-chamber system (see Figure 6) and a two-chamber system (additional electrode in the right atrium), vector2 is preferably utilized, both for the morphological signal analysis and for generating the signal window trigger. For a typical CRT system (see Figure?) there is the option for the signal window triggers of feeding these via vector 3, while utilizing a more strongly filtered signal in combination with an auto-sense unit. This may be advantageous with respect to the signal-to-noise ratio in relation to potential movement artifacts of the patient or myopotentials. Furthermore, a three-chamber system provides the option of reconfiguring the lead for the delivery of the ATP stimulation pulses from vectorl to vector3 and utilizing vectorl in such a case for the signal window trigger generation.

[0202] • The “Computation and storage of features of the current signal window“ was previously described in Figure 10.

[0203] • The “Reference formation for the signal window“ represents the options against which signal the current window or the morphological features from the current window are compared so as to ascertain the morphological distance as a scalar value.

[0204] • “Running predecessor window”: here, the immediate predecessor or the second-to-last predecessor or the predecessor having the distance N can be used as the reference window.

[0205] • “Static predecessor window”: here, for example, the first ATP stimulation pulse is utilized as the reference window for all further beat-wise evaluations.

[0206] • “Averaged predecessor window”: A mean value is formed of N consecutive signal windows per morphological window, and this respective averaged value is used per morphological feature as a reference variable (e.g., a “virtual” morphology is created, which does not have to have been present this way in reality).

[0207] • “Physiological pre-detection beat”: for example, the last beat leading to the detection of the episode and thus to the start of the ATP therapy or the signal window of which as a reference window for all further morphological comparisons.

[0208] • “Stimulated pre-detection beat”: for example, last stimulation pulse in ATP pacing lead (vectorl), but not older than a time period of, for example, 24 h.

[0209] • The “Determination of the difference between reference window and current signal window“: Here, the scalar value, referred to as “morphological distance” is determined (described in Figure 10).

[0210] The individual morphological feature differences could be offset with weighting factors before creating the sum so as to weaken or upgrade the significance of individual features. This also goes

[0211] 23.164P-WO / / 12.03.2026hand in hand with the option of weakening basically correlated features compared to uncorrelated ones. This represents an alternative to the use of, for example, features normalized to max_Peak2Peak .

[0212] Figure 12 depicts the symbol key used by the subsequent timing diagrams in Figures 13 - 18.

[0213] In Figures 13 - 18, the temporal flow for a specific scenario for the beat-wise entrainment evaluation is schematically shown in each case. In Figures 14 - 18, the illustration is divided into six horizontal tracks.

[0214] The top two tracks represent the sensing points in time of the physiological and stimulated events, symbolized by stars, from the view of the active implant. To the left next to the track, the vector used is shown (for definitions see Figures 6 and 7).

[0215] At the discrete points in time n=l...N, perpendicular dotted lines show the points in time of the morphological feature extraction or signal window triggers. The signal features for the reference window and the current evaluation window are illustrated symbolically by a crosshatched area having a variable shape in the third and fourth tracks. The fifth track shows the progression of the signal feature difference (scalar value - morphological distance) qualitatively as a characteristic curve, as well as the threshold values for the “morphological onset” and “entrainment”.

[0216] The last track in Figures 14 - 18 serves as a symbolic representation of the entrainment sensor status. The cross symbolizes an inactive entrainment sensor (for example, during pre-detection phase), and the exclamation mark shows an active entrainment sensor in which no onset was yet recognized. The hook symbolizes a recognized morphological onset, and the hook with the heart symbolizes a recognized entrainment.

[0217] Figure 13 depicts a timing diagram with ATP delivered on vector 1 or vector3 (“Stimulation”) and far-field sensing on vector2, along with signal window triggers (dashed lines) and the resulting signal windows on which the morphological features are calculated. The temporal trigger points arise from a signal evaluation of vector2 by determining the R waves by means of state-of-the-art QRS detector algorithms (for example, based on Pan-Tompkins algorithm). It can be seen that obtaining triggers from vector2 permits an uninterrupted morphology analysis despite pacing on a separate vector.

[0218] 23.164P-WO / / 12.03.2026Figure 14 shows an exemplary beat- wise morphological entrainment evaluation with the predecessor window. The triggering of the signal windows is driven by vector2. For the reference window, the features from the direct predecessor window are applied at each point in time n. The pre-detection phase runs until point in time n=l, during which the beat-wise entrainment evaluation is inactive. Thereafter, the transition to ATP therapy sequence phase 1 and the delivery of the first ATP stimulation pulses take place. At the point in time n=2, the signal feature difference between the reference and evaluation windows is determined for the first ATP stimulation pulse. The influence of the ATP stimulation pulse on the signal features or the area takeover thereof is schematically symbolized in the figure by the change in the crosshatched shapes from a square to a trapezoid. The signal feature difference is below the threshold value for the morphological onset. At the point in time n=3, the signal feature difference is above the threshold value, and the status of the entrainment sensor switches to “Onset recognized.” After the recognized morphological onset, it is checked for the subsequent stimulation pulses when the signal features remain stable or the signal feature difference drops below the threshold value for the entrainment recognition. In the example, the signal features have a stable progression starting at the point in time n=5, and the entrainment is recognized.

[0219] Figure 15 depicts an exemplary beat-wise morphological entrainment evaluation with an averaged reference window. It is shown that the triggering of the signal windows is driven by vector2. For the reference window, the averaged features from the three predecessor windows are calculated at each point in time n. The pre-detection phase runs until point in time n=3, during which the beat-wise entrainment evaluation is inactive. Thereafter, the transition to ATP therapy sequence phase 1 and the delivery of the first ATP stimulation pulses take place . At the point in time n=4, the signal feature difference between the reference window and the signal window is determined for the first ATP stimulation pulse. The signal feature difference exceeds the threshold value for the morphological onset so that the status of the entrainment sensor switches to “Onset recognized.” After the recognized morphological onset, it is checked for the subsequent stimulation pulses when the signal features remain stable or the signal feature difference drops below the threshold value for the entrainment recognition. In the example, the signal features have a stable progression starting at the point in time n=6, and the entrainment is recognized.

[0220] Figure 16 shows an exemplary beat-wise morphological entrainment evaluation with pre-detection and the predecessor window. It is shown that the triggering of the signal windows is driven by vector2. Compared to exemplary embodiments shown in Figures 13, 14 and 15, different signal features are utilized, which is symbolized by the differing shapes. In this example, the reference window is dependent on the status of the entrainment sensor. Beginning with the start of ATP therapy

[0221] 23.164P-WO / / 12.03.2026sequence phase 1, a static window is utilized for the morphological onset recognition, which is determined from the last signal window of the pre-detection phase. In the example, the features of the current window are compared against the features from the point in time n=l during each evaluation in the ATP therapy sequence phase 1 up until the point in time n=4. As soon as the signal feature difference exceeds the threshold for the morphological onset, the reference window is dynamically determined, as in the exemplary embodiment of Figure 14, by applying the features from the immediate predecessor. Starting with the point in time n=6, the signal feature difference drops below the threshold value for recognition of the entrainment, and the overall process switches to ATP therapy sequence phase 2.

[0222] Figure 17 illustrates an exemplary beat- wise morphological entrainment evaluation with X out of Y criterion for the entrainment recognition. It is shown that the triggering of the signal windows is driven by vector2. The reference window is dynamically determined from the predecessor window. In the example, the morphological onset is recognized at the point in time n=0. For the recognition of the entrainment, an X out of Y criterion is employed (by way of example where X=3, Y=5). At the point in time n=5, the signal feature difference within five evaluation windows has dropped below the threshold value for the entrainment three times so that the entrainment is recognized.

[0223] Figure 18 shows an exemplary beat-wise entrainment evaluation from the temporal distance between the stimulation pulse and the signal window trigger. For that embodiment, a temporal criterion for recognizing the entrainment is required in addition to the morphological evaluation. For this purpose, the interval length between the ATP stimulation pulse and the trigger for the signal window is measured for every point in time n. It is furthermore necessary that the deviation of the current interval from the predecessor interval is within a stability corridor or between an upper and a lower threshold value (alternatively, the increase can also be checked against a threshold value). The threshold values are adapted to the current interval length after each check. In the example, the entrainment is morphologically recognized at the point in time n=4. The status of the entrainment sensor, however, remains on “Onset recognized” since additionally the stability of the stimulation pulse trigger interval is required for confirming the entrainment. At the point in time n=5, the interval is within the stability corridor so that the entrainment is recognized by the sensor.

[0224] According to further embodiments, parameters can be derived from the introduced beat-based entrainment evaluation and be transmitted together with the intra-cardiac electrogram data and / or as part of regular status messages for systems connected downstream (for example, remote monitoring or the programming device). For the potential customers (e.g. a responsible clinical employee), e.g.

[0225] 23.164P-WO / / 12.03.2026a scoring system could be derived as to which ATP pacing patterns that, even though they ultimately did not result in termination, are still fed back for the identified “influence” of the ATP stimulation pulses on the tachycardia according to embodiments of the invention.

[0226] Likewise, it appears useful to collect the recognized number of necessary ATP stimulation pulses until entrainment is recognized, while simultaneously storing the TCL together with each ATP attempt with entrainment evaluation carried out in a beat-wise manner, as well as the coupling time for the ATP therapy sequence phase 1 stimulation pulses (“RS 1 interval”) changed in the meantime by the clinician within a data set.

[0227] Two groups of patients can be formed from this data set.

[0228] A.) successful termination across multiple ATP attempts with a count of necessary therapy sequence phase 1 stimulation pulses that exceeds a predetermined threshold,

[0229] B.) successful termination across multiple ATP attempts, with little variance of the number of necessary ATP therapy sequence phase 1 stimulation pulses identified by the beat-wise entrainment evaluation.

[0230] C.)

[0231] For Group A, this results in the potential of sending a warning to the clinician that the ATP therapy is not considered optimal by the configured pacing vector.

[0232] As a result (for example, in the case of CRT systems), the vector setup for the ATP therapy could be adapted. Alternatively, the subsequent therapy configuration is to be adapted by the clinician, within the meaning of an optimization of “time to success” of the therapy.

[0233] 23.164P-WO / / 12.03.2026DEFINITIONS

[0234] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Terms such as "including," "comprising," and "having" are used in an open-ended sense, and do not exclude additional elements or steps. The terms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "first," "second," and the like are used as labels to distinguish different instances, and do not necessarily imply an order, priority, or temporal sequence, unless the context clearly indicates otherwise. The term "and / or" indicates any one of the referenced items, or any combination of the referenced items.

[0235] "Implantable medical device" (IMD) refers to an apparatus configured for implantation in a human or animal body and configured to deliver anti-tachycardia pacing (ATP) therapy and to sense one or more physiological signals, including one or more electrical signals of the heart, using electrode poles and associated circuitry.

[0236] "Electrode pole" refers to an electrically conductive element configured to be used to sense an electrical signal and / or to deliver an electrical pulse.

[0237] "Electrode-pole pair" refers to a pair of electrode poles used together to define a sensing vector and / or a stimulation vector.

[0238] "Vector" refers to an electrical configuration defined by at least two electrode poles used for sensing and / or stimulation.

[0239] "Therapy sequence" refers to a sequence comprising at least one electrical pulse delivered to the heart.

[0240] "Anti-tachycardia pacing" (ATP) refers to delivery of one or more pacing pulses intended to terminate or modify a tachycardia.

[0241] "Event" refers to a detected occurrence derived from a sensed signal.

[0242] "Tachycardia condition" refers to a detected condition based on events and time intervals between events indicating tachycardia.

[0243] 23.164P-WO / / 12.03.2026"Tachycardia cycle length" (TCL) refers to a cycle length determined from time intervals between detected events associated with a tachycardia condition.

[0244] "Post-pacing interval" refers to a time interval between a last stimulation pulse of a therapy sequence and a first detected intrinsic cardiac event after the last stimulation pulse.

[0245] "Parameter" refers to a quantity derived from detected events and / or characteristics of sensed signals and used by a control unit to generate and / or adapt a therapy sequence.

[0246] "Phase offset" refers to a temporal offset between events associated with a first tachycardia condition and events associated with a second tachycardia condition, as determined after delivery of a therapy sequence.

[0247] "Entrainment" refers to a positive therapeutic effect in which delivered stimulation pulses take over a reentry mechanism associated with a tachycardia.

[0248] "Morphology" refers to waveform shape characteristics of a sensed cardiac electrical signal.

[0249] "Control unit," "detection unit," "stimulation unit," and "memory unit" refer to functional units of the IMD as described herein.

[0250] 23.164P-WO / / 12.03.2026LIST OF REFERENCE SIGNS

[0251] 100 implantable medical device (IMD) 110 heart

[0252] 111 electrode poles

[0253] 120 stimulation unit

[0254] 130 detection unit

[0255] 140 control unit

[0256] 150 memory unit

[0257] 200 therapy sequence

[0258] 209 cycle length (CL)

[0259] 210 tachycardia cycle length (TCL) 210b observation window

[0260] 211 tachycardia cycle length (TCL) 211b observation window

[0261] 220 coupling interval (RSI)

[0262] 230 inter-pulse interval (SISI)

[0263] 231 shortened inter-pulse interval 300 tachycardia

[0264] 301 tachycardia cycle length

[0265] 302 intrinsic cardiac event

[0266] 303 intrinsic cardiac event

[0267] 305 first vector

[0268] 306 second vector

[0269] 310 therapy sequence

[0270] 311 planned pulse

[0271] 320 temporal relationship

[0272] 330 pacing interval

[0273] 331 pacing interval

[0274] 340 interval between sensed events 341 interval between sensed events 400 progression of interval values 500 rhythm segment

[0275] 510 rhythm segment

[0276] 511 waveform

[0277] 23.164P-WO / / 12.03.2026600 implantable system

[0278] 611 analog / digital converter, filter, offset compensation 615 communication unit

[0279] 620 right ventricular (RV) electrode / lead

[0280] 621 RV tip electrode pole

[0281] 622 RV ring electrode pole

[0282] 623 coil electrode pole

[0283] 624 vector 1

[0284] 625 vector2

[0285] 630 left ventricular (LV) electrode / lead

[0286] 631 LV tip electrode pole

[0287] 632 LV ring electrode pole

[0288] 633 vector3

[0289] 634 LV ring2 electrode pole

[0290] 635 LV ring3 electrode pole

[0291] 700 programming device

[0292] 701 communication unit

[0293] 800 remote service center

[0294] 23.164P-WO / / 12.03.2026

Claims

Claims1. Implantable medical device (IMD) for anti-tachycardia pacing (ATP) of a heart, comprising:- at least three electrode poles configured to sense electrical signals of the heart and / or to apply electrical pulses to the heart,- a stimulation unit, configured to deliver the electrical pulses to the heart via at least two of the electrode poles, wherein the stimulation unit is configured to deliver at least one therapy sequence to the heart, wherein the therapy sequence comprises at least one electrical pulse,- 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, andii. derive at least one parameter based on the events,the stimulation unit is configured to deliver a first therapy sequence comprising at least one electrical pulse to the heart if the detection unit detects a first tachycardia condition based on a plurality of first events, wherein the first therapy sequence is delivered via a first pair of electrode poles of the at least three electrode poles, characterized in thatthe detection unit is configured to detect events in the sensed electrical signals via a second pair of electrode poles of the at least three electrode poles during the delivery of the first therapy sequence, wherein at least one electrode pole of the second pair of electrode poles is different from the electrode poles of the first pair of electrode poles,wherein the control unit is configured to generate at least a first parameter based on the events detected during delivery of the first therapy sequence, wherein the first parameter is associated with an effect to the heart caused by the first therapy sequence, and wherein the control unit is configured to generate at least one second therapy sequence based on the first parameter.

2. IMD according to claim 1, wherein the detection unit is configured to analyze at least one of the following characteristics in the events detected during delivery of the first therapy sequence:23.164P-WO / / 12.03.2026- a patern 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,wherein the control unit is configured to generate the at least one first parameter based on the at least one characteristic.

3. IMD according to claim 1 or 2, wherein the electrode poles of the first pair of electrode poles are located on a first electrode lead, and wherein the electrode poles of the second pair of electrode poles are located on a second electrode lead.

4. IMD according to at least one of the preceding claims, wherein at least one electrode pole of the first pair of electrode poles has a distance of at least 10mm to at least one electrode pole of the second pair of electrode poles.

5. IMD according to at least one of the preceding claims, wherein the first pair of electrode poles and the second pair of electrode poles are located such that the pairs operate in different chambers of the heart.

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

7. IMD according to claim 6, wherein the at least one first electrical pulse- is part of the first therapy sequence, or23.164P-WO / / 12.03.2026is delivered by the stimulation unit when no tachycardia condition has been detected by the detection unit.

8. IMD according to at least one of the preceding claims, wherein the control unit is configured to switch between pairs of electrode poles for delivering electrical pulses and / or to switch between pairs of electrode poles for detecting the sensed electrical signals.

9. IMD according to at least one of the preceding claims, wherein the detection unit is configured to detect 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, and wherein the control unit is configured to generate the first parameter and / or a second parameter based on the post-pacing interval.

10. IMD according to claim 9, wherein the detection unit is configured to detect- 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, and- a second post-pacing 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,wherein the control unit is configured to generate the first parameter and / or the second parameter based on the difference between the first and the second post-pacing interval.

11. IMD according to at least one of the preceding claims, wherein the detection unit is configured to- detect a second tachycardia condition based on a plurality of second events in the sensed electrical signals after delivery of the first therapy sequence, - determine a phase offset between the first events and the second events, and wherein the control unit is configured to generate the first parameter and / or a second parameter based on the phase offset.

12. IMD according to at least one of the preceding claims, wherein at least one electrode pole is at least a part of a housing of the IMD, and / or wherein at least one electrode pole is located to detect electrical signals from a left ventricle of the heart.23.164P-WO / / 12.03.202613. IMD according to at least one of the preceding claims, wherein the control unit is configured to generate the second therapy sequence based on the first parameter by adjusting at least one of the following parameters:- a duration of the second therapy sequence,- a number of pulse series of the second therapy sequence,- a number of pulses of the second therapy sequence,- a pulse width of at least one electrical pulse of the first and / or second therapy sequence,- an inter-pulse-interval between at least two pulses of the second therapy sequence, - a coupling interval between a last pulse of the events having a tachycardia condition and the first pulse of the second therapy sequence.

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

15. Method for operating an implantable medical device (IMD) for stimulating a human or animal heart, characterized by the following steps:- detect a first tachycardia condition based on a plurality of first events in an electrical signal of the heart,- deliver a first therapy sequence comprising at least one electrical pulse to the heart via a first pair of electrode poles,- detect events in the sensed electrical signals via a second pair of electrode poles during the delivery of the first therapy sequence, wherein at least one electrode pole of the second pair of electrode poles is different from the electrode poles of the first pair of electrode poles,- generate at least a first parameter based on the events detected during delivery of the first therapy sequence, wherein the first parameter is associated with an effect to the heart caused by the first therapy sequence,- generate at least one second therapy sequence based on the first parameter.23.164P-WO / / 12.03.2026

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