Implantable medical device enabling a discrimination between a ventricular tachycardia and a supraventricular tachycardia

Abstract

The present invention relates to an implantable medical device (1) for stimulating a human or animal heart. During operation, the implantable medical device (1) executes a method comprising the following steps: a) determining a ventricular rhythm and determining a rate of the ventricular rhythm; b) if the rate of the ventricular rhythm exceeds a first predeterminable threshold and is thus indicative for a ventricular tachycardia, providing an atrial antitachycardia pacing; c) determining an influence of the atrial antitachycardia pacing on the ventricular rhythm; and d) classifying the ventricular rhythm as representing a supraventricular tachycardia if an influence of the atrial antitachycardia pacing on the ventricular rhythm was determined; otherwise classifying the ventricular rhythm as representing a ventricular tachycardia.

Description

[0001] Applicant: BIOTRONIK SE & Co. KG

[0002] Date: 09.03.2026

[0003] Our Reference: 23.086P-WO

[0004] Implantable medical device enabling a discrimination between a ventricular tachycardia and a supraventricular tachycardia

[0005] The present invention relates to an implantable medical device according to the preamble of claim 1 and to a method for operating an implantable medical device according to the preamble of claim 14.

[0006] Implantable medical devices for stimulating a human or animal heart, such as pacemakers, have been known for a long time. They can perform different functions. Different stimulation programs can be carried out by an appropriate pacemaker to restore the treated heart to a normal state.

[0007] To give an example, pacemakers can be used as defibrillation system. Such a defibrillation system, also known as an implantable cardioverter-defibrillator (ICD), is used to recognize and treat potentially life-threatening cardiac arrhythmias (ventricular tachycardia, bradycardia, ventricular fibrillation). Such a defibrillation system is implanted in a patient in such a way that one or more electrode leads extend from a defibrillation generator to the human heart in order to detect signals for the purpose of recognizing cardiac arrhythmia and to emit stimulation energy, in particular to cause an electric shock (defibrillation). Both the electrode leads and the defibrillation generator are permanently implanted and remain in the patient for a long period of time, usually several years.

[0008] Defibrillation shocks should only be delivered by an ICD if the treated heart is in a physiologic state in which it is susceptible to such a defibrillation shock. This is typically true in case of ventricular tachycardia. However, if a patient experiences a supraventricular tachycardia, defibrillation shocks are to be avoided since they are associated with an increased mortality and with pain for the patient. Thus, there is a need to safely discriminate a ventricular tachycardia (VT) from a supraventricular tachycardia (SVT). Prior art devices already perform an SVT / VT discrimination on the basis of an evaluation of timing-based criteria. Here, the (ventricular) onset of a tachycardic episode and the stability of a ventricular rhythm are the most important criteria. In addition, morphologic features of an electrogram can be evaluated. Such evaluations are typically based on a comparability between an observed QRS complex with a reference such as a previously stored QRS complex.Multi-chamber ICD systems also include further criteria regarding the relation between the ventricular activity and the atrial activity to make an SVT / VT discrimination. To give some examples, a relation between the mean current atrial rate and the mean current ventricular rate, the monotony of the atrioventricular conduction time, N:1 relations between ventricular activity and atrial activity and atrioventricular conduction times as well as ventriculoatrial conduction times are already used as additional elements for SVT / VT discrimination. Furthermore, the stability of the atrial rhythm is considered in prior art multi-chamber ICD systems as further timing criterion for performing an SVT / VT discrimination.

[0009] Yalin et al. (Yalin, Kivanc, et al. "Postpacing interval during right ventricular overdrive pacing to discriminate supraventricular from ventricular tachycardia." Journal of Atrial Fibrillation 10.2 (2017)) describes the use of the post pacing interval (P-PI) for differentiating ventricular tachycardia from supraventricular tachycardia.

[0010] Cardoso et al. (Cardoso, Rhanderson N., et al. "ICD discrimination of SVT versus VT with 1: 1 VA conduction: A review of the literature." Indian Pacing and Electrophysiology Journal 15.5 (2015): 236-244) provides a review of the literature on different techniques for performing an SVT / VT discrimination.

[0011] It is generally possible to optimize the already existing SVT / VT discrimination possibilities, e.g., by combining the performed analysis with a drug delivery. However, the identification of patients in whom an SVT was incorrectly classified as VT often takes only place after a false-positive rhythm classification has been made and an inadequate shock therapy has already been delivered.

[0012] It is an object of the present invention to ameliorate the SVT / VT discrimination of implantable medical devices such as ICD systems.

[0013] This object is achieved with an implantable medical device having the features of claim 1.

[0014] This object is achieved with an implantable medical device for stimulating a human or animal heart according to claim 1. Such an implantable medical device comprises a processor, a memory unit, a stimulation unit, and a detection unit. The stimulation unit serves for stimulating a human or animal heart. The detection unit serves for detecting an electric signal of the same heart, i.e., a cardiac electric signal. The implantable medical device further comprises a first electrode for detecting atrial electric signals and for providing stimulation pulses to an atrium of the heart and a second electrode for detecting ventricular electric signals and for providing stimulation pulses to a ventricle of the heart.

[0015] 23.086P-WO / 09.03.2026Thus, the first electrode and the second electrode both form part of the detection unit and of the stimulation unit.

[0016] According to an aspect of the present invention, the memory unit comprises a computer-readable program that causes the processor to perform the steps explained in the following when being executed on the processor.

[0017] In a first step (step a)), a ventricular rhythm is determined with the detection unit and the second electrode. In addition, a rate of the ventricular rhythm is determined.

[0018] Afterwards, it is determined if the rate of the ventricular rhythm exceeds a first predeterminable threshold (step b)). If this is the case, the rate of the ventricular rhythm is considered to be indicative for ventricular tachycardia, i.e., a ventricular tachycardia is suspected. However, the rate could generally also be indicative for a supraventricular tachycardia. To allow an S VT / VT discrimination, an atrial antitachycardia pacing (aATP) is provided with the stimulation unit and the first electrode.

[0019] Afterwards, it is determined whether the atrial antitachycardia pacing has an influence on the ventricular rhythm (step c)). This determination can be done qualitatively, quantitatively, or semi-quantitatively.

[0020] Finally, the ventricular rhythm is classified to represent a supraventricular tachycardia if an influence of the atrial antitachycardia pacing on the ventricular rhythm was determined (step d)). If, however, no such influence could be determined, the ventricular rhythm is classified to represent ventricular tachycardia.

[0021] This SVT / VT discrimination based on an atrial antitachycardia pacing is much more reliable and accurate than SVT / VT discriminations known from prior art. In addition, the atrial antitachycardia pacing is much less painful for the patient. The safe and reliable SVT / VT discrimination avoids inadequate shock therapies and increases the quality of life of the patient by avoiding mental and physiologic stress, by reduction of hospitalizations and by increasing the lifetime of the implant due to less power consumption (because a lower overall number of shocks is provided by the implantable medical device). The provision of the atrial antitachycardia pacing can also have a positive sideeffect that the origin of the tachycardic ventricular rhythm is not only correctly recognized to be supraventricular, but that the cause is successfully treated.

[0022] The risk associated with the provision of an atrial antitachycardia pacing is considerably low. Generally, the atrial antitachycardia pacing results in a (minimal) delay of a shock therapy that is

[0023] 23.086P-WO / 09.03.2026optionally provided after having provided the atrial antitachycardia pacing. If the atrial antitachycardia pacing induces in case of a ventricular-driven rhythm additionally an atrial tachycardia, this atrial tachycardia will very likely be terminated upon the delivery of the subsequent shock therapy. In any case, the benefit of the SVT / VT discrimination by an atrial antitachycardia pacing for avoiding potentially inadequate shocks is considered to be significantly higher than the previously explained risk.

[0024] In an embodiment, the supraventricular tachycardia (SVT) includes at least one of atrial fibrillation (AF), atrial flutter, sinus tachycardia, atrial tachycardia, atrioventricular (AV) reentrant tachycardia, and AV nodal reentrant tachycardia (AVNRT).

[0025] In an embodiment, the implantable medical device comprises a data communication unit that serves for receiving data from a remote programming device in a wireless manner. Optionally, the data communication unit serves for transferring data to the remote programming device. With the help of the programming device, it is particularly simple to parametrize the components of the implantable medical device. All standard data transmission protocols or specifications are appropriate for such a wireless data communication. Examples of standard data transmission protocols or specifications are the Medical Device Radiocommunications Service (MICS), the Bluetooth Low Energy (BLE) protocol, the Zigbee specification, the long range wide area network (LoRaWAN) protocol, the wireless personal area network (WPAN) specification, the low-power wide-area network (LPWAN) specification, the wireless local area network (WLAN) specification, the Global System for Mobile Communications (GSM) specification, the Long-Term Evolution (LTE) standard, and the fifthgeneration technology standard for broadband cellular networks (5G).

[0026] In an embodiment, the computer-readable program causes the processor to receive, via the communication unit, data from an external programming device. This data serves to parametrize the individual components of the implantable medical device, in particular of the detection unit and / or the stimulation unit. In an embodiment, the communication unit does not only receive data from an external programming device, but is also able to provide data to the external programming device. Then, an information exchange between the external programming device and the implantable medical device is made particularly simple.

[0027] In an embodiment, the computer-readable program causes the processor to inhibit the provision of a ventricular antitachycardia pacing with the stimulation unit and the second electrode if the ventricular rhythm is classified as representing a supraventricular tachycardia. By such inhibition, a physiologic insensible and potentially health-threatening ventricular antitachycardia pacing (such as a

[0028] 23.086P-WO / 09.03.2026defibrillation shock or a series of defibrillation shocks) is sufficiently prevented. This results in the positive aspects of the avoidance of inadequate shock therapies explained above.

[0029] In an embodiment, the computer-readable program causes the processor to provide a ventricular antitachycardia pacing with the stimulation unit and the second electrode if the ventricular rhythm is classified as representing a ventricular tachycardia. Such a delivery of a ventricular antitachycardia pacing is an appropriate measure to attempt to terminate a ventricular tachycardia. Thus, if the SVT / VT discrimination resulted in a classification of the ventricular rhythm as originating from a ventricular tachycardia, the provision of a ventricular antitachycardia pacing is an appropriate measure since it can terminate a potentially life-threatening cardiac condition.

[0030] In an embodiment, the computer-readable program causes the processor to provide a predeterminable first amount of ventricular antitachycardia pacings and to then repeat the steps of determining a ventricular rhythm and determining the rate of the ventricular rhythm (step a)), providing an atrial antitachycardia pacing if the rate of the ventricular rhythm is indicative for ventricular tachycardia (step b)), determining an influence of the atrial antitachycardia pacing on the ventricular rhythm (step c)), and classifying the ventricular rhythm either as originating from a ventricular tachycardia or from a supraventricular tachycardia in dependence on the influence of the atrial antitachycardia pacing (step d)). Afterwards, a predeterminable second amount of ventricular antitachycardia pacings is provided if the ventricular rhythm is classified as representing a ventricular tachycardia in the repeated classification step. By such a sequence of method steps, all ventricular antitachycardia pacings that are available according to the present set of parameters of the implantable medical device are spent in order to achieve a classification of the previously determined ventricular tachycardia. Repeating the previously mentioned steps allows a re-detection of a possibly persisting ventricular tachycardia. In such a case, which represents a health-threatening or even life-threatening cardiac state, it is expedient to provide further ventricular antitachycardia pacings to the heart to be treated in order to achieve a termination of the ventricular tachycardia in the second attempt. Since the second amount of ventricular antitachycardia pacings is only delivered if a persisting ventricular tachycardia is determined by repeated steps a) to d), an unnecessary delivery of ventricular antitachycardia pacings is avoided.

[0031] In an embodiment, the computer-readable program causes the processor to provide the atrial antitachycardia pacing during a predeterminable first period of time. This predeterminable first period of time can be set as parameter in the implantable medical device. It can be defined in terms of an objective time period (e.g., several seconds) or in form of a relative period of time dependent on the cardiac rhythm of the patient. The first period of time is chosen such that the probability increases to determine the ventricular rhythm during the atrial antitachycardia pacing as well as the

[0032] 23.086P-WO / 09.03.2026stability of the ventricular rhythm during the atrial antitachycardia pacing in a robust manner. This would not be the case if the predeterminable first period of time is chosen too short.

[0033] In an embodiment, the predeterminable first period of time covers 5 to 20, in particular 6 to 19, in particular 7 to 18, in particular 8 to 17, in particular 9 to 16, in particular 10 to 15, in particular 11 to 14, in particular 12 to 13 mean R-R intervals (i.e., intervals lasting from the R wave of a first QRS complex to the R wave of the immediately adj acent QRS complex) of the ventricular rhythm, wherein the ventricular rhythm is the rhythm of the ventricle before providing the atrial antitachycardia pacing. A minimum number of five mean R-R intervals makes it possible to analyze at least four ventricular, in particular right ventricular, events so that three R-R intervals can be determined during the atrial antitachycardia pacing that represent the minimum requirement for a safe determination of the mean R-R interval and the stability of the mean R-R interval during the atrial antitachycardia pacing.

[0034] In an embodiment, the computer-readable program causes the processor to determine an atrial rhythm with a detection unit and the first electrode, to compare this atrial rhythm with a ventricular rhythm and to perform the steps b) to d) only if a 1:1 relation between the atrial rhythm and the ventricular rhythm is identified upon comparing the atrial rhythm with the ventricular rhythm. Such a prerequisite for performing steps b) to d) is particularly helpful for safely discriminating an SVT from a VT. If there is a 1 : 1 relation between the atrial rhythm and ventricular rhythm, it is more likely that the heart is in a state of supraventricular tachycardia. On the other hand, if no 1:1 relation between the atrial rhythm and the ventricular rhythm can be detected, is quite likely that the tachycardic ventricular rhythm is independent from an also tachycardic atrial rhythm so that it would be quite unlikely to achieve any significant effect on the ventricle by providing an atrial antitachycardia pacing. To avoid any time loss, a ventricular antitachycardia pacing can be provided in such a situation without first providing an atrial antitachycardia pacing.

[0035] In an embodiment, a 1 : 1 relation between the atrial rhythm and the ventricular rhythm is considered to be present if a deviation between the atrial rhythm and the ventricular rhythm lies below a third predeterminable threshold. In an embodiment, the atrial rhythm and the ventricular rhythm are compared on the basis of mean atrial intervals (mean P-P intervals) and mean ventricular intervals (mean R-R intervals). In an embodiment, the predeterminable third threshold - relating to atrial intervals and ventricular intervals to be compared - lies in a range of from 10 ms to 50 ms, in particular from 15 ms to 45 ms, in particular from 20 ms to 40 ms, in particular from 25 ms to 35 ms, in particular from 30 ms to 35 ms.

[0036] 23.086P-WO / 09.03.2026In an embodiment, the computer-readable program causes the processor to perform step c), i.e., the step of determining an influence of the atrial antitachycardia pacing and the ventricular rhythm, by assessing whether at least 1 of the following conditions is fulfdled.

[0037] According to a first condition, the rate of the ventricular rhythm directly after the atrial antitachycardia pacing needs to still lie above the first predeterminable threshold (which is indicative for a tachycardic behavior of the ventricle).

[0038] According to a second condition, a 1 : 1 relation between atrial electric signals and ventricular electric signals can be confirmed.

[0039] According to a third condition, a decrease of the rate of the ventricular rhythm in response to the atrial antitachycardia pacing exceeds a second predeterminable threshold.

[0040] According to a fourth condition, the stability of the ventricular rhythm has decreased in response to the atrial antitachycardia pacing.

[0041] Step d) of the method performed by the implantable medical device is then carried out such that the ventricular rhythm is classified as representing a supraventricular tachycardia if the first condition is not fulfilled. I.e., if the ventricular rhythm directly after the atrial antitachycardia pacing lies below the first predeterminable threshold, the ventricle has terminated its tachycardic state and returned to a non-tachycardic state, e.g., to a physiologic state. In such a case, a ventricular antitachycardia pacing would be particularly insensible and without any medical indication. Therefore, a classification of the observed tachycardia as supraventricular tachycardia (and optionally an inhibition of the ventricular antitachycardia pacing) is particularly appropriate.

[0042] The ventricular rhythm results are classified to represent a supraventricular tachycardia if the first condition is fulfilled (i.e., if the tachycardic state of the ventricle still persists) and the second condition is fulfilled (i.e., if a 1:1 relation between atrial electric signals and ventricular electric signals can be confirmed) and at least one of the third and fourth condition is also fulfilled. I.e., if the rate of the ventricular rhythm has decreased to a certain extent in response to the atrial antitachycardia pacing and / or the stability of the ventricular rhythm has decreased in response to the atrial antitachycardia pacing, this clearly indicates that there has been an influence of the atrial antitachycardia pacing to the ventricular rhythm. This in turn means that the ventricular activity is not completely dissolved from the atrial activity so that a supraventricular tachycardia is more likely than an isolated ventricular tachycardia. Consequently, a classification of the observed tachycardic state of the ventricle as supraventricular tachycardia is justified. However, in all other cases, i.e., in

[0043] 23.086P-WO / 09.03.2026all other combinations of fulfilled / non-fulfilled conditions, the ventricular rhythm is classified to represent a ventricular tachycardia.

[0044] In an embodiment, the second predeterminable threshold lies in a range of from 30 beats per minute (bpm) to 150 bpm, in particular from 40 bpm to 140 bpm, in particular from 50 bpm to 130 bpm, in particular from 60 bpm to 120 bpm, in particular from 70 bpm 110 bpm, in particular from 80 bpm to 100 bpm, in particular from 90 bpm to 95 bpm.

[0045] In an embodiment, the stability of the ventricular rhythm has decreased in response to the atrial antitachycardia pacing to fulfil the fourth condition by 5 percentage points to 100 percentage points, in particular by 10 percentage points to 95 percentage points, in particular by 15 percentage points to 85 percentage points, in particular by 20 percentage points to 80 percentage points, in particular by 25 percentage points to 75 percentage points, in particular by 30 percentage points to 70 percentage points, in particular by 35 percentage points to 65 percentage points, in particular by 40 percentage points to 60 percentage points, in particular by 45 percentage points to 55 percentage points, in particular by 50 percentage points to 55 percentage points.

[0046] Generally, it is not necessary to test the first to fourth conditions in the indicated order. However, this is done in an embodiment. Furthermore, it is not necessary to assess the fulfilment of all the conditions. In an embodiment, at least two of the four conditions are tested with respect to fulfilment. In an embodiment, the first condition is not the only condition, the fulfilment of which is assessed.

[0047] In an embodiment, the computer-readable program causes the processor to assess the fulfilment of the second condition only if the first condition is fulfilled. If the first condition is not fulfilled, the observed tachycardia of the ventricle can be classified as supraventricular tachycardia. In such a case, it would generally not be necessary to assess the fulfilment of a further condition.

[0048] In an embodiment, the computer-readable program causes the processor to assess the fulfilment of at least one of the third condition and the fourth condition only if the second condition is fulfilled. If the second condition is not fulfilled, the observed tachycardia is to be classified as ventricular tachycardia, irrespective of the fulfilment of the third of fourth condition. Therefore, it is not necessary to test the fulfilment of these conditions.

[0049] In an embodiment, the computer-readable program causes the processor to assess the fulfilment of the third condition or the fourth condition only if the respective other of the third condition and the fourth condition is not fulfilled. Since it is typically sufficient if one of the third and fourth conditions is fulfilled (and the second condition is fulfilled) to classify the observed tachycardia as

[0050] 23.086P-WO / 09.03.2026supraventricular tachycardia, it is not necessary to test the fulfilment of the respective other of the third condition and fourth condition.

[0051] All reductions of the number of conditions, the fulfilment of which is to be assessed, results in a faster classification of the observed tachycardia either as supraventricular tachycardia or as ventricular tachycardia. In addition, the consumption of less computational and power resources of the implantable medical device is achieved by a reductions of the number of conditions, the fulfilment of which is to be assessed.

[0052] In an embodiment, the computer-readable program causes the processor to compare a morphology of the QRS complex observed in a far-field electrogram on the one hand directly before provision of the atrial antitachycardia pacing and on the other hand during provision of the atrial antitachycardia pacing. By such a comparison it is possible to determine an influence of the atrial antitachycardia pacing on the ventricular rhythm by evaluating morphologic criteria. This can assist the classification of the observed tachycardia as supraventricular tachycardia or as ventricular tachycardia and can make the classification even more reliable. To give some examples, windowing, feature extraction and / or concrete comparison are appropriate techniques for comparing the morphology of the QRS complexes.

[0053] In an embodiment, the computer-readable program causes the processor to identify ventricular events during the atrial antitachycardia pacing from a far-field electrogram. Even though this is technically more demanding than a direct determination of the ventricular activity from the signal detected by the second electrode, relying on a far-field electrogram reduces the risk of cross-channel blanking during the provision of the atrial antitachycardia pacing that might hinder reliable ventricular event extraction from the detected signals.

[0054] In an embodiment, the implantable medical device comprises a third electrode for detecting left ventricular electric signals or for detecting electric signals of the conduction system of the heart. In this embodiment, the computer-readable program causes the processor to identify ventricular events during the atrial antitachycardia pacing with a third electrode. Also in this embodiment, the potential cross-channel blanking of signals detected by the second electrode is avoided. Extracting information on the (right) ventricular activity not only by an extraction of information from electric signals recorded from the (right) ventricle, but also from other sites of the heart, can generally increase the reliability of the obtained information and thus can increase the accuracy of the method performed by the implantable medical device.

[0055] 23.086P-WO / 09.03.2026In an aspect, the present invention relates to a method for operating an implantable medical device for stimulating a human or animal heart, in particular an implantable medical device according to the preceding explanations. In this context, the method comprises the steps explained in the following.

[0056] In a first step (step a)), a ventricular rhythm is determined with a detection unit and a second electrode. In addition, a rate of the ventricular rhythm is determined.

[0057] Afterwards, it is determined if the rate of the ventricular rhythm exceeds a first predeterminable threshold (step b)). If this is the case, the rate of the ventricular rhythm is considered to be indicative for a ventricular tachycardia, i.e., a ventricular tachycardia is suspected. However, the rate could generally also be indicative for a supraventricular tachycardia. To allow an S VT / VT discrimination, an atrial antitachycardia pacing (aATP) is triggered. This atrial antitachycardia pacing can generally be delivered with the stimulation unit and the first electrode.

[0058] Furthermore, it is determined whether the atrial antitachycardia pacing has (or has had) an influence on the ventricular rhythm (step c)). This determination can be done qualitatively, quantitatively, or semi -quantitatively.

[0059] Finally, the ventricular rhythm is classified to represent a supraventricular tachycardia if an influence of the atrial antitachycardia pacing on the ventricular rhythm was determined (step d)). If, however, no such influence could be determined, the ventricular rhythm is classified to represent ventricular tachycardia.

[0060] In an aspect, the present invention relates to a method for discriminating between a ventricular tachycardia and a supraventricular tachycardia of a heart of a patient in need of such discrimination with an implantable medical device for stimulating a human or animal heart, in particular an implantable medical device according to the preceding explanations. In this context, the method comprises the steps explained in the following.

[0061] In a first step (step a)), a ventricular rhythm is determined with a detection unit and a second electrode. In addition, a rate of the ventricular rhythm is determined.

[0062] Afterwards, it is determined if the rate of the ventricular rhythm exceeds a first predeterminable threshold (step b)). If this is the case, the rate of the ventricular rhythm is considered to be indicative for a ventricular tachycardia, i.e., a ventricular tachycardia is suspected. However, the rate could generally also be indicative for a supraventricular tachycardia. To allow an S VT / VT discrimination, an atrial antitachycardia pacing (aATP) is provided with the stimulation unit and the first electrode.

[0063] 23.086P-WO / 09.03.2026Furthermore, it is determined whether the atrial antitachycardia pacing has (or has had) an influence on the ventricular rhythm (step c)). This determination can be done qualitatively, quantitatively, or semi -quantitatively.

[0064] Finally, the ventricular rhythm is classified to represent a supraventricular tachycardia if an influence of the atrial antitachycardia pacing on the ventricular rhythm was determined (step d)). If, however, no such influence could be determined, the ventricular rhythm is classified to represent ventricular tachycardia.

[0065] According to a different aspect, an implantable medical device for anti-tachycardia pacing (ATP) is proposed that delivers a first therapy sequence via a first pair of electrode poles configured to stimulate at least a part of an atrium. A detection unit senses electrical signals and detects events during or after delivery of the first therapy sequence. A control unit generates at least one parameter associated with the effect of the first therapy sequence on the heart and, based on that parameter, adjusts the first therapy sequence and / or generates a second therapy sequence. Optional embodiments position the first pair on an atrial or near-atrial lead (e.g., right atrium, near the AV node, coronary sinus near the left atrium, or extracardial near the atrium) and provide a second pair of electrode poles for ventricular stimulation so that atrial and ventricular therapy sequences can be delivered in a coordinated or independent manner. Additional features include analyzing patterns and morphologies of events, thresholds, extrema, slope or curvature to form parameters; selecting preferred sensing or stimulating electrode pairs based on delay times or entrainment conditions; and detecting entrainment via post-pacing intervals and / or propagation times. The implantable medical device may be a pacemaker, implantable cardioverter-defibrillator, cardiac resynchronization therapy device, or a conduction system pacing device. The approach supports dynamic, automated adaptation of ATP tailored to atrioventricular tachycardias.

[0066] According to this different aspect, an implantable medical device for anti-tachycardia pacing (ATP) is disclosed that comprises at least a first pair of 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 electrical pulses to the heart via at least the first pair of electrode poles as at least one therapy sequence, 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, and a control unit configured to generate at least one therapy sequence and 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 comprising at least one electrical pulse via the first pair of electrode poles. The first pair of electrode

[0067] 23.086P-WO / 09.03.2026poles is configured to stimulate at least a part of an atrium. During or after delivery of the first therapy sequence, the detection unit detects events in the sensed electrical signals via one pair of electrode poles, and the control unit generates at least a first parameter based on the events detected during or after delivery of the first therapy sequence, the first parameter being associated with an effect to the heart caused by the first therapy sequence, and 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. Delivering the first therapy sequence to the atrium while evaluating events during or after delivery allows dynamic, automated adaptation of ATP to patient-specific tachycardia, particularly in atrioventricular reentry tachycardias such as AVNRT or WPW, and results in more agile therapy than fixed ATP schemes.

[0068] According to an embodiment, the implantable medical device can include an electrode lead comprising the first pair of electrode poles, wherein the electrode lead is implanted in the atrium or near the atrium of the heart, for example in the right atrium, near the AV node, in the coronary sinus near the left atrium, or extracardially near the atrium, such as less than five centimeters. Positioning the first pair near the AV node or in the coronary sinus targets typical reentry circuits in atrioventricular tachycardias and facilitates entrainment and capture with fewer pulses, thereby improving therapy efficiency.

[0069] The implantable medical device can for example further comprise at least a second pair of electrode poles configured to stimulate the right or left ventricle of the heart, and the stimulation unit can deliver a second therapy sequence via the first or the second pair of electrode poles. Providing both atrial and ventricular stimulation sites enables coordinated or alternative ATP attempts and improves the likelihood of timely entrainment from the side that responds best.

[0070] According to an embodiment, for the events detected during or after delivery of the first therapy sequence, the detection unit can analyze at least one characteristic selected from 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, crossing of a predefined threshold, or extrema, maximum slope, or curvature, wherein the control unit generates the at least one first parameter based on the at least one characteristic. Evaluating temporal patterns and morphological criteria enables robust discrimination between successful capture or entrainment and ineffective or pro-arrhythmic responses, which in turn supports on-the-fly parameter adaptation.

[0071] For example, the control unit can adjust the first therapy sequence and / or generate 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 pulses of at least one of the pulse series of

[0072] 23.086P-WO / 09.03.2026the first and / or 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 first and / or second therapy sequence, or 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. Such dynamic adjustments within an ongoing ATP attempt can raise therapy success rates, reduce pulse count and duration, and mitigate adverse effects such as acceleration.

[0073] Moreover, according to an embodiment, the control unit can generate at least one ventricular parameter for adjusting or generating at least one therapy sequence for stimulating a ventricle of the heart, and at least one atrial parameter for adjusting or generating at least one therapy sequence for stimulating the atrium of the heart, and the stimulation unit can deliver the therapy sequence for stimulating a ventricle of the heart and the therapy sequence for stimulating the atrium of the heart in a coordinated manner and / or independently. Treating atrial and ventricular reactions separately enables channel-specific optimization and timing coordination across the atrioventricular junction for atrioventricular reentry tachycardias.

[0074] According to an embodiment, the detection unit can detect second events in the sensed electrical signals via at least two pairs of electrode poles as an effect to the heart caused by the delivery of at least one first electrical pulse, and can 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, and the control unit can 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. Selecting the pair with the longest delay can reduce stimulus-artefact contamination and improve the fidelity of post-pacing event detection, which stabilizes parameter generation for subsequent adaptations.

[0075] For example, the stimulation unit can deliver at least one therapy sequence via at least two pairs of electrode poles that are configured to stimulate in the same chamber of the heart, and the detection unit can detect an effect of each therapy sequence, and the control unit can select the pair of electrode poles for further application of electrical pulses to the heart which showed the best effect, wherein 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 between delivery of the therapy sequence and detection of the entrainment condition, wherein an entrainment condition is detected if at least one therapy sequence succeeded in capturing the heart. Comparing multiple stimulation sites within a chamber and choosing the site that achieves entrainment fastest or with the fewest pulses increases efficiency and may reduce pro-arrhythmic risk.

[0076] 23.086P-WO / 09.03.2026Moreover, according to an embodiment, the entrainment condition can be detected if the detection unit detects a post-pacing interval between a last pulse of a previous therapy sequence preceding the first therapy sequence and a first detected intrinsic cardiac event after the last pulse of the previous therapy sequence, wherein the length of the post-pacing-interval exceeds an entrainment threshold, and / or if the control unit controls the timing of at least one therapy sequence 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, and wherein the control unit determines 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, and the second electrode pole is located on a second electrode lead. Using post-pacing intervals and propagation-time -based timing yields robust entrainment assessment and more precise sequence timing, and multi-lead sensing further improves capture verification.

[0077] For instance, the detection unit can 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 the control unit can generate the first parameter based on the at least one postpacing interval. Deriving the first parameter from the post-pacing interval provides a direct quantitative measure of the therapy effect on the tachycardia and enables targeted adjustments in real time.

[0078] According to an embodiment, the detection unit can 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, and the control unit can generate at least the first parameter based on the difference between the first and the second post-pacing interval. Comparing post-pacing intervals across sequences allows the control unit to rank strategies and converge on an effective therapy sequence with minimal pulses and duration.

[0079] Moreover, according to an aspect, after delivery of the first therapy sequence, the detection unit can detect a second tachycardia condition based on a plurality of second events in the sensed electrical signals, determine a phase offset between the first events and the second events, and the control unit can generate at least the first parameter based on the phase offset. Incorporating phase offset analysis improves discrimination of partial capture versus full entrainment and informs timing of subsequent therapy sequences.

[0080] 23.086P-WO / 09.03.2026For example, at least one pair of electrode poles can be configured to detect a far-field signal, characterized in that a first electrode pole is located in or at a heart chamber and a second electrode pole is located outside of the same heart chamber. Far-field signals enhance temporal context across chambers and support entrainment detection and cross-channel timing control.

[0081] According to an embodiment, at least one electrode pole can be at least a part of a housing of the implantable medical device. Using the housing as an electrode pole can simplify the lead system and provide a stable reference for far-field sensing or stimulation.

[0082] For instance, the implantable medical device can be a cardiac pacemaker, an implantable cardioverter-defibrillator, a cardiac rhythm management therapy device, and / or a conduction system pacing device, and the disclosed ATP adaptation can be implemented across these device classes, including transvenous and extravascular configurations, enabling broad applicability to atrioventricular tachycardias.

[0083] Moreover, according to the different aspect, a method for operating an implantable medical device for stimulating a heart comprises 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 an atrium of the heart via a first pair of electrode poles, detecting events in the sensed electrical signals via one pair of electrode poles during or after delivery of the first therapy sequence, generating at least a first parameter based on the events detected during or after 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 adjusting the first therapy sequence based on the first parameter and / or generating at least one second therapy sequence based on the first parameter. This method operationalizes closed-loop ATP in which sensed events during or after an attempt directly inform real-time sequence adaptation, shortening therapy duration and reducing the number of pulses required while targeting atrioventricular reentry substrates.

[0084] The different aspect described above is in the following numbered embodiments summarized: 1. Implantable medical device (IMD) for anti -tachycardia pacing (ATP) of a heart, comprising:

[0085] - at least a first pair of electrode poles configured to sense electrical signals of the heart and / or to apply electrical pulses to the heart,

[0086] - a stimulation unit, configured to deliver the electrical pulses to the heart via at least the first pair of 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,

[0087] 23.086P-WO / 09.03.2026- 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,

[0088] - A control unit, configured to:

[0089] i. generate at least one therapy sequence, and

[0090] ii. derive at least one parameter based on the events,

[0091] 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 the first pair of electrode poles,

[0092] characterized in that

[0093] the first pair of electrode poles is configured to stimulate at least a part of an atrium of the heart,

[0094] wherein the detection unit is configured to detect events in the sensed electrical signals via one pair of electrode poles during or after delivery of the first therapy sequence,

[0095] and wherein the control unit is configured to generate at least a first parameter based on the events detected during or after 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 adjust the first therapy sequence based on the first parameter, and / or generate at least one second therapy sequence based on the first parameter.

[0096] IMD according to embodiment 1, comprising an electrode lead comprising the first pair of electrode poles, and wherein the electrode lead is implanted in the atrium or near the atrium of the heart, wherein the lead is implanted in the right atrium, near the AV node, in the coronary sinus near the left atrium, or extracardially near the atrium (e.g. < 5 cm).

[0097] IMD according to embodiment 1 or 2, comprising at least a second pair of electrode poles, wherein the second pair of electrode poles is configured to stimulate the right or left ventricle of the heart, wherein the stimulation unit is configured to deliver the second therapy sequence via the first or second pair of electrode poles.

[0098] IMD according to at least one of the preceding embodiments, wherein the detection unit is configured to analyze at least one of the following characteristics in the events detected during or after delivery of the first therapy sequence:

[0099] - a pattern in a plurality of time intervals between intrinsic cardiac activities and / or paced pulses caused by the first therapy sequence,

[0100] - a morphology of at least one event of the events,

[0101] 23.086P-WO / 09.03.2026- crossing of a predefined threshold,

[0102] - extrema, maximum slope, or curvature,

[0103] wherein the control unit is configured to generate the at least one first parameter based on the at least one characteristic.

[0104] IMD according to at least one of the preceding embodiments, wherein the control unit is configured to adjust the first therapy sequence and / or to generate the second therapy sequence based on the first parameter by adjusting at least one of the following parameters:

[0105] - a duration of the first and / or second therapy sequence,

[0106] - a number of pulses of at least one of the pulse series of the first and / or second therapy sequence,

[0107] - a pulse width of at least one electrical pulse of the first and / or second therapy sequence,

[0108] - an inter-pulse-interval between at least two pulses of the first and / or second therapy sequence,

[0109] - 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.

[0110] IMD according to at least one of the preceding embodiments, wherein the control unit is configured to generate at least one ventricular parameter for adjusting or generating at least one therapy sequence for stimulating a ventricle of the heart, and at least one atrial parameter for adjusting or generating at least one therapy sequence for stimulating the atrium of the heart,

[0111] and wherein the stimulation unit is configured to deliver the at least one therapy sequence for stimulating a ventricle of the heart, and the at least one therapy sequence for stimulating the atrium of the heart in a coordinated manner and / or independently.

[0112] IMD according to at least one of the preceding embodiments, wherein the detection unit is configured to

[0113] - 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

[0114] - 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,

[0115] 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

[0116] 23.086P-WO / 09.03.2026electrical signals.

[0117] IMD according to at least one of the preceding embodiments, wherein the stimulation unit is configured to deliver at least one therapy sequence via at least two pairs of electrode poles, wherein the two pairs of electrode poles are configured to stimulate in the same chamber of the heart,

[0118] and wherein the detection unit is configured to detect an effect of each of the therapy sequences, and wherein the control unit is configured to select the pair of electrode poles for further application of electrical pulses to the heart which showed the best effect, wherein 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 between delivery of the therapy sequence and detection of the entrainment condition,

[0119] wherein an entrainment condition is detected if at least one therapy sequence succeeded in capturing the heart.

[0120] IMD according to embodiment 8, wherein the entrainment condition is detected

[0121] - if the detection unit detects a post-pacing interval between a last pulse of a previous therapy sequence preceding the first therapy sequence, and a first detected intrinsic cardiac event after the last pulse of the previous therapy sequence, wherein the length of the post-pacing-interval exceeds an entrainment threshold, and / or - if the control unit is configured to control the timing of at least one therapy sequence based on at least one propagation time, the propagation time 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, and wherein the control unit is configured to determine the propagation time based on at least one signal parameter from the sensed electrical signals,

[0122] and / or

[0123] - via an additional electrode pole, wherein the first electrode pole is located on a first electrode lead, and the second electrode pole is located on a second electrode lead.

[0124] IMD according to at least one of the preceding embodiments, 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 based on the at least one post-pacing interval.

[0125] 23.086P-WO / 09.03.2026IMD according to embodiment 10, 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

[0126] - 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,

[0127] 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.

[0128] IMD according to at least one of the preceding embodiments, wherein the detection unit is configured to

[0129] - detect a second tachycardia condition based on a plurality of second events in the sensed electrical signals after delivery of the first therapy sequence,

[0130] - determine a phase offset between the first events and the second events,

[0131] and wherein the control unit is configured to generate at least the first parameter based on the phase offset.

[0132] IMD according to at least one of the preceding embodiments, wherein at least one pair of electrode poles is configured to detect a far-field signal, characterized in that the first electrode pole is located in or at a heart chamber, and the second electrode pole is located outside of the same heart chamber.

[0133] IMD according to at least one of the preceding embodiments, wherein at least one electrode pole is at least a part of a housing of the IMD.

[0134] IMD according to at least one of the preceding embodiments, wherein the IMD is a cardiac pacemaker, an implantable cardioverter-defibrillator (ICD), a cardiac rhythm management therapy (CRT) device, and / or a conduction system pacing (CSP) device.

[0135] Method for operating an implantable medical device (IMD) for stimulating a human or animal heart, characterized by the following steps:

[0136] - detect a first tachycardia condition based on a plurality of first events in an electrical signal of the heart,

[0137] - deliver a first therapy sequence comprising at least one electrical pulse to an atrium of the heart via a first pair of electrode poles,

[0138] 23.086P-WO / 09.03.2026- detect events in the sensed electrical signals via one pair of electrode poles during or after delivery of the first therapy sequence,

[0139] - generate at least a first parameter based on the events detected during or after delivery of the first therapy sequence, wherein the first parameter is associated with an effect to the heart caused by the first therapy sequence,

[0140] - adjust the first therapy sequence based on the first parameter, and / or generate at least one second therapy sequence based on the first parameter.

[0141] All embodiments of the implantable medical device can be combined in any desired way and can be transferred either individually or in any arbitrary combination to the described methods. Likewise, all embodiments of the described methods can be combined in any desired way and can be transferred either individually or in any arbitrary combination to the implantable medical device or the respective other method.

[0142] Further details of aspects of the present invention will be explained in the following making reference to exemplary embodiments and accompanying Figures. In the Figures:

[0143] Figure 1A schematically shows a system comprising an implantable medical device;

[0144] Figure IB schematically shows different components of the implantable medical device of Figure 1A;

[0145] Figure 2A shows a flowchart on the individual method steps performed by an embodiment of an implantable medical device;

[0146] Figure 2B illustrates the temporal sequence of different therapies applied by the implantable medical device of Figure 2A;

[0147] Figure 3 illustrates an example for the automatic detection of the amount of stimuli for defining a time period during which an atrial antitachycardia pacing is applied;

[0148] Figure 4 schematically illustrates the course of cardiac signals during an SVT / VT discrimination in relation to a first condition assessed by an SVT / VT discrimination module;

[0149] Figure 5 schematically illustrates the course of cardiac signals during an SVT / VT discrimination in relation to a second condition assessed by an SVT / VT discrimination module; and

[0150] 23.086P-WO / 09.03.2026Figure 6 schematically illustrates the course of cardiac signals during an SVT / VT discrimination in relation to a third and a fourth condition assessed by an SVT / VT discrimination module;

[0151] Figure 1A shows a system comprising an implantable cardioverter-defibrillator (ICD) 1 as example of an implantable medical device for stimulating the human or animal heart. The system further comprises a programming device 2 serving as remote programming system. It is possible for the ICD device 1 to establish a wireless data communication with the programming device 2.

[0152] The ICD device 1 comprises a housing 3 with a header 4 and a first electrode 5 connected to the header 4. The first electrode 5 comprises a first tip electrode pole 6 and a first ring electrode pole 7 that is proximally arranged from the first tip electrode pole 6. A first sensing vector 8 is defined from the first ring electrode pole 7 to the first tip electrode pole 6. Electric cardiac signals sensed between the first tip electrode pole 6 and first the ring electrode pole 7, i.e., along the first sensing vector 8, are directly recorded within a heart chamber, typically the right atrium. Thus, the first electrode 5 is designed and arranged to sense right atrial electric signals.

[0153] The ICD device 1 additionally comprises a second electrode 9 that is also connected to the header 4. The second electrode 9 comprises a second tip electrode pole 10 and a second ring electrode pole 11 that is proximally arranged from the second tip electrode pole 10. A second sensing vector 12 is defined from the second ring electrode pole 11 to the second tip electrode pole 10. Electric cardiac signals sensed between the second tip electrode pole 10 and the second ring electrode pole 11, i.e., along the second sensing vector 12, are also directly recorded within a heart chamber, typically the right ventricle. Thus, the second electrode 9 is designed and arranged to sense right ventricular electric signals.

[0154] Figure IB schematically illustrates individual components of the ICD device 1 that are comprised within the housing 3. In this and in all following Figures, similar elements will be denoted with the same numeral reference. The housing 3 houses a detection unit 31 (also referred to as sensing unit) that typically comprises an analog -to-digital converter, a bandpass filter, and an offset compensation. The detection unit 31 is operatively connected with a processor 32 that has access to a memory unit 33. The memory unit 33 serves for storing instructions for the processor 32 as well as data detected by the detection unit 31. The housing 3 further comprises an evaluation unit 34 that can also be part of the processor 32 and that serves for extracting features from the detected cardiac electric signal. The housing 3 further comprises a stimulation unit 35 that serves for stimulating the heart from which the detection unit 31 detects electric signals. The first electrode 5 along with its first tip electrode pole 6 and first ring electrode pole 7 as well as the second electrode 9 along with its second tip

[0155] 23.086P-WO / 09.03.2026electrode 10 and second ring electrode 11 (confer Figure 1A) form part of the detection unit 31 and of the stimulation unit 35. Additionally, the housing 3 comprises a data communication unit 36 that serves for data transfer to the programming device 2 (confer Figure 1 A). The housing 3 additionally comprises an SVT / VT discriminator module 37 that can be present in the housing 3 as own module, as own circuitry, or as part of any of the other units.

[0156] Figure 2A shows a schematic flowchart illustrating the individual steps of an SVT / VT discrimination performed according to an embodiment. The "classic" signals (sources), namely a right ventricular sensing 200, a right atrial sensing 210 and far-field morphology 220 are used to provide features or criteria. E.g., the right ventricular sensing 200 provides exclusive right ventricular timing features 201 such as the onset of tachycardiac episodes or the R-R stability). Likewise, the right atrial sensing 210 provides exclusive right atrial timing features 211 such as the P-P stability. In addition, both the right ventricular sensing 200 and the right atrial sensing 210 provide combined right atrial and right ventricular timing features 205 such as an N:1 relation between right atrial signals and right ventricular signals, a 1:1 relation between right atrial signals and right ventricular signals, atrioventricular delays, ventriculoatrial delays, and an atrioventricular monotony. The far-field morphology 220 provides morphologic features 221 such as a QRS width and a similarity between the QRS complex and a QRS reference complex. All of these features 201, 205, 211, and 221 are used for an initial detection 230 of a suspected tachycardia.

[0157] In a first decision step 240, it is determined whether there exists a 1 : 1 relation between the right atrial signals and the right ventricular signals. If this is the case (indicated by the letter "Y") an atrial antitachycardia pacing 241 A is delivered. In a parallel evaluation step 24 IB, it is determined if there is a reaction in the ventricle to this atrial antitachycardia pacing 241 A, i.e., if the atrial antitachycardia pacing 241 A has an influence on the ventricular rhythm. The steps of providing the atrial antitachycardia pacing 241A and the parallel evaluation 24 IB of the ventricle in response to this atrial antitachycardia pacing is performed by an SVT / VT discriminator module 37 that forms part of the implantable medical device which carries out the presently described method. Since the SVT / VT discriminator module 37 performs the SVT / VT discrimination by the delivery of an atrial antitachycardia pacing (aATP), it can also be referred to as aATP-SVT / VT discriminator module 37. If a reaction in the ventricle can be detected, an antegradely conducted ventricular rhythm is assumed. It is further assumed that the tachycardic ventricular rhythm cannot be terminated by the provided atrial antitachycardia pacing (since the tachycardic ventricular rhythm still persists). In such a case, the episode originally classified as ventricular tachycardia is reclassified as a supraventricular tachycardia.

[0158] 23.086P-WO / 09.03.2026In a further decision step 242, it is checked whether the SVT / VT discriminator module 37 has detected a supraventricular tachycardia. If this is the case (Y), it is finally classified in classification step 247 as supraventricular tachycardia so that no further ventricular antitachycardia pacing therapies are provided by the implantable medical device.

[0159] If, however, the SVT / VT discriminator module 37 has not safely detected a supraventricular tachycardia (letter "N" in decision step 242), a further decision step 243 is performed. In this further decision step 243, it is checked whether already all available ventricular antitachycardia pacing therapies have been provided. If this is not the case (N), all programmed ventricular antitachycardia pacing therapies can be provided in step 244. Afterwards, a re-detection step 245 is performed in which it is checked if there still exists a 1 : 1 relation between the atrial rhythm and the ventricular rhythm and if a parameter set is activated that allows the delivery of a further atrial antitachycardia pacing. If both conditions are met (Y), the method continues with step 241 A and 24 IB carried out by the SVT / VT discriminator module 37. If, however, not both conditions are met in step 245 (N), the method continues to step 246 in which all programmed shock therapies are provided. Likewise, if it has been determined in the further decision step 243 that all available ventricular antitachycardia pacing therapies have already been delivered, the method directly continues to step 246 in which all programmed shock therapies are delivered.

[0160] The SVT / VT discriminator module 37 receives a parametrization 250 from an external device so that the functionality of the SVT / VT discriminator module 37 can be adjusted to the concrete needs of a specific patient.

[0161] Figure 2B illustrates the temporal sequence of the individually applied therapies. Upon a start 260 of the method, a first atrial antitachycardia pacing 261 is applied. This is done in the SVT / VT discriminator module 37. The step 261 corresponds to step 241A of Figure 2A if the latter is performed as first atrial antitachycardia pacing of the sequence of pacings. If a supraventricular tachycardia is recognized in decision step 262 at the output side of the SVT / VT discriminator module 37 (Y), the detected tachycardic episode is reclassified as supraventricular tachycardia. As a consequence, no further re-detection (illustrated by circle in Figure 2B) is performed, and no further therapy is delivered to the heart. Thus, step 269 of Figure 2B is comparable with step 247 of Figure 2A.

[0162] If, however, in the decision step 262 a supraventricular tachycardia cannot be safely recognized (N), a couple of ventricular antitachycardia pacing therapies 263 is applied sequentially. This is illustrated by a first ventricular antitachycardia pacing 264, a second ventricular antitachycardia pacing 265 and an N-th ventricular antitachycardia pacing 266. A further prerequisite of the delivery of each of the

[0163] 23.086P-WO / 09.03.2026ventricular antitachycardia pacing therapies 263 is a re-detection of a ventricular tachycardic rhythm that cannot be safely classified as supraventricular tachycardia.

[0164] In step 267, a second atrial antitachycardia pacing is provided by the S VT / VT discriminator module 37 and evaluated by this module. In a subsequent decision step 268 (which is comparable to the decision step 262 and the decision step 242 of Figure 2A) it is once again checked if the detected tachycardia rhythm can be safely classified as supraventricular tachycardia. If this is the case (Y), the method terminates at step 269 (see above for more explanations). If this, however, is not the case (N), a plurality of shock therapies 270 is applied. These shock therapies 270 are illustrated in Figure 2B by a first shock therapy 271 and an N-th shock therapy 272. Like in case of providing the ventricular antitachycardia pacing therapy, it is also a prerequisite of providing one of the shock therapies 270 that a tachycardic ventricular rhythm was confirmed by a re-detection.

[0165] The programming of the S VT / VT discriminator 37 can be made in a dialogue for setting the ventricular detection of the implantable medical device. If the user clicks in an activated VT zone in the corresponding field, an additional dialogue is presented in which the parameters of the atrial antitachycardia pacing delivery can be set. To make the assessment of the ventricular rhythm even more robust, a minimum duration T2 is required for the atrial antitachycardia pacing therapy. This minimum duration is automatically chosen if an "AUTO" option is activated for the parameter "P-S1 interval". This will be explained in more detail in Figure 3.

[0166] Figure 3 shows a schematic depiction of right atrial (RA) and right ventricular (RV) electric signals. At the start point 300 directly upon an initial detection of a tachycardic ventricular rhythm that is suspected to be a ventricular tachycardia, an atrial antitachycardia pacing is provided. This is done by a plurality of atrial antitachycardia pacing stimuli 301. The provision of these atrial antitachycardia pacing stimuli 301 corresponds to step 241 A in Figure 2A and the first atrial antitachycardia pacing 261 of Figure 2B. The atrial antitachycardia pacing shall be provided for first period of time T2 that shall have a minimum duration. Figure 3 explains, how this duration is automatically detected and set. Generally, T2 should correspond to a duration of at least six times the mean R-R interval before the onset of the tachycardic episode (meanRRl), i.e., T2 = 6* meanRRl.

[0167] This minimum duration is requested to obtain quite safely at least five RV events so that four ventricular intervals can be determined during the atrial antitachycardia pacing delivery. The number of four intervals is particularly appropriate to determine the mean R-R intervals during the atrial antitachycardia pacing (meanRR2) and the stability of the ventricular rhythm during the atrial

[0168] 23.086P-WO / 09.03.2026antitachycardia passing (stabRR2). Assuming thatmeanRRl is 300 ms (corresponding to 200 bpm), T2 would be 1.8 seconds.

[0169] Assuming a coupling time of 80 % (suitable coupling times lie in a range from 70 % to 95 %, in particular from 75 % to 90 %, in particular from 80 % to 85 %) of the first stimulus (P-Sl interval factor = 0.8), an amount N_aATP_stimuli of N = 8 results.

[0170] In more abstract terms, the amount of stimuli N aATP stimuli can be calculated as follows:

[0171] N aATP stimuli = T2 / ( P-Sl interval factor*meanRRl)

[0172] N aATP stimuli = 6*meanRRl / ( P-Sl interval factor*meanRRl)

[0173] N_aATP_stimuli = 6 / P-S 1 interval factor

[0174] Considering that only whole-number stimuli can be parametrized, the result is rounded up:

[0175] N_aATP_stimuli = ROUNDUP(6 / P-S1 interval factor)

[0176] Generally, a second period of time T1 (alternatively, a defined amount of ventricular events) should be waited to determine the mean ventricular interval meanRR3 after termination of the atrial antitachycardia pacing. This second period of time T1 helps for identifying a termination of a tachycardic ventricular rhythm due to the atrial antitachycardia pacing. In such a case, the original tachycardic ventricular rhythm can be classified as supraventricular tachycardia.

[0177] Theoretically, it would be possible that upon an unfavorable choice of specific parameters (namely a particularly long minimum evaluation time for specific conditions to be fulfilled and a particularly short redetection waiting time) redetection conditions are already met prior to the termination of the minimum evaluation time for a specific condition. To avoid such a situation, Figure 4 illustrates appropriate examples of individual parameters of the SVT / VT discriminator module.

[0178] The parameter meanRRl indicates the mean interval length of the consecutive four R-R intervals directly before the atrial antitachycardia pacing delivery 401. The parameter meanRR3 indicates the mean interval length of all R-R intervals that are located within the second time period T1 (i.e., the R-R intervals after termination of the atrial antitachycardia pacing 401). To assess if the first condition is met, namely if the rate of the ventricular rhythm directly after the atrial antitachycardia pacing still lies above the first predeterminable threshold (which is indicative for a tachycardic rhythm), all four events shall be evaluated that are located in a time window that corresponds to the second time period T1 that is calculated as T1 = 5*meanRRl . In this context, the second time period T1 starts with the first ventricular event after termination of the atrial antitachycardia pacing.

[0179] 23.086P-WO / 09.03.2026If the ventricular rhythm would be unchanged by the atrial antitachycardia pacing 401 (thus, if the ventricular rhythm would continue with an interval length of approximately meanRRl), it would be possible to detect five ventricular events within the second time period T1. Thus, it would be possible to rely on four ventricular intervals for calculating the parameter meanRR3.

[0180] If the ventricular rhythm is slower, a lower number of ventricular intervals is used for calculating the parameter meanRR3. As can be seen from Figure 4, the atrial antitachycardia pacing 401 resulted in a decrease of the rate of the ventricular rhythm so that three ventricular intervals are used for calculating the mean ventricular interval meanRR3.

[0181] It is then checked if the first condition is met, i.e., if the rate of the ventricular rhythm directly after the atrial antitachycardia pacing still lies above the first predeterminable threshold, i.e., if the mean interval length of all R-R intervals that are located within the second time period T1 is shorter than or equal to a programmed VT interval corresponding to the first predetermined threshold in the time domain (#1: meanRRB < programmed VT interval).

[0182] Figure 5 illustrates a risk reducing measure of the SVT / VT discriminator module. For the rather hypothetical case that during or because of the atrial antitachycardia pacing delivery a ventricular tachycardia develops in an originally supraventricular tachycardia, a risk reducing measure can be integrated into the SVT / VT discriminator module.

[0183] The aim of this risk reducing measure is to check whether a 1 : 1 relation between the atrial electric signals and the ventricular electric signals can still be confirmed (second condition). Such a check is only necessary if the ventricular rhythm is considered to be tachycardic (# 1 : meanRR3 < programmed VT interval). All R-R intervals within the second period of time T1 are averaged to obtain the mean R-R interval after termination of the atrial antitachycardia pacing 501 (meanRR3). Likewise, all P-P intervals lying within the second time period T1 are averaged to obtain a mean P-P interval meanPPpost. Afterwards, meanRR3 and meanPPpost are compared. If they deviate from each other by more than the threshold Ito I tolerance (which is - in the exemplary embodiment of Figure 5 -20 ms), a 1 : 1 relation between the atrial signals at the ventricular signals is considered to be not confirmed (#2: | meanPPpost - meanRR3 | > ltol_tolerance)). Consequently, the current tachycardic ventricular rhythm without 1:1 relation to the atrial signals is to be classified as ventricular tachycardia.

[0184] In a variant of the embodiment illustrated in Figure 5, the mean ventricular interval meanRR3 after termination of the atrial antitachycardia pacing 501 is compared with the mean interval length of the

[0185] 23.086P-WO / 09.03.2026four atrial intervals directly preceding the atrial antitachycardia pacing 501. This mean interval length is denoted as meanPPpre. By such a comparison, a ventricular tachycardia induced during or directly after the delivery of the atrial antitachycardia pacing therapy can be identified, wherein the ventricular tachycardia has then a retrograde conduction.

[0186] Alternatively or additionally, a 1 : 1 relation cannot only be tested with respect to the averaged interval length, but also by considering the atrioventricular delay 502 and / or the ventriculoatrial delay 503 before and after the atrial antitachycardia pacing delivery. Only if the atrioventricular delay 502 and the ventriculoatrial delay 503 are almost constant before and after the atrial antitachycardia pacing, a continuous 1 : 1 relation between atrial and ventricular events can be assumed.

[0187] The classification of the detected ventricular rhythm by the SVT / VT discriminator module will be explained in more detail making reference to Figure 6.

[0188] The parameter “tolerance” is a value that can be parameterized by a user. It serves as a threshold value for the classification. This value can be applied to the parameters "meanRR tolerance" and "stabRR tolerance" .

[0189] The parameter meanRRl denotes again the mean interval length of the four R-R intervals directly before the atrial antitachycardia pacing delivery. The parameter meanRR2 indicates the mean interval length of all R-R intervals during the atrial antitachycardia pacing 601.

[0190] The parameter meanRR3 denotes again the mean interval length of all R-R intervals within the second time period T1 that starts upon termination of the atrial antitachycardia pacing 601. The parameter stabRRl is the stability value of the ventricular rhythm directly before the atrial antitachycardia pacing 601. E.g., the standard deviation of the four R-R intervals used for calculating meanRRl can be used for the parameter stabRRl.

[0191] The parameter stabRR2 is the stability value of the ventricular rhythm during the atrial antitachycardia pacing 601. It can be calculated from the standard deviation of all R-R intervals observed during the atrial antitachycardia pacing 601. The top and middle panel of Figure 6 illustrate examples for assessing if the third condition (a change of the rate of the ventricular rhythm during the atrial antitachycardia pacing exceeds a second predeterminable threshold) is fulfilled. The bottom panel of Figure 6 illustrates an example for the fulfilment of the fourth condition (the stability of the ventricular rhythm has decreased in response to the atrial antitachycardia pacing).

[0192] 23.086P-WO / 09.03.2026In the top panel of Figure 6. the first condition is fulfilled, but the second condition is not fulfilled during the atrial antitachycardia pacing. In addition, the third condition is not fulfilled since the rate of the ventricular rhythm has not significantly decreased during the atrial antitachycardia pacing (#3 : (meanRRl-meanRR2) / meanRRl < meanRR tolerance). Rather, it is quite similar to the rate of the ventricular rhythm before the atrial antitachycardia pacing. Therefore, the observed ventricular rhythm is classified to be representative for a ventricular tachycardia. Subsequently, a ventricular antitachy cardie pacing can be applied.

[0193] In the middle panel of Figure 6, the first and second condition are fulfilled. Here, also a significant decrease of the ventricular rhythm with respect to the ventricular rhythm during the atrial antitachycardia pacing is observed (#2: (meanRRl-meanRR2) / meanRRl > meanRR tolerance). Thus, obviously, the atrial antitachycardia pacing has had a direct influence on the ventricular rhythm. Consequently, the observed ventricular rhythm is considered to be representative for a supraventricular tachycardia.

[0194] The bottom panel of Figure 6 illustrates an example for the fourth condition. While the ventricular rhythm was rather stable before the start of the atrial antitachycardia pacing, it changed to an instable rhythm during the atrial antitachycardia pacing (#3: stabRRl < stabRR tolerance AND stabRR2 > stabRR tolerance). Due to the fulfilment of the fourth condition, the observed ventricular rhythm is classified to represent a supraventricular tachycardia (the atrial antitachycardia pacing had obviously an influence onto the ventricular rhythm).

[0195] 23.086P-WO / 09.03.2026

Claims

Claims1. Implantable medical device (1) for stimulating a human or animal heart, comprising a processor (32), a memory unit (33), a stimulation unit (34) configured to stimulate a human or animal heart, a detection unit (31) configured to detect an electric signal of the same heart, a first electrode (5) for detecting atrial electric signals and for providing stimulation pulses to an atrium of the heart, and a second electrode (9) for detecting ventricular electric signals and for providing stimulation pulses to a ventricle of the heart,characterizedin that the memory unit (33) comprises a computer-readable program that causes the processor (32) to perform the following steps when being executed on the processor (32):a) determining a ventricular rhythm with the detection unit (31) and the second electrode (9) and determining a rate of the ventricular rhythm;b) if the rate of the ventricular rhythm exceeds a first predeterminable threshold and is thus indicative for a ventricular tachycardia, providing an atrial antitachycardia pacing with the stimulation unit (34) and the first electrode (5);c) determining an influence of the atrial antitachycardia pacing on the ventricular rhythm;andd) classifying the ventricular rhythm as representing a supraventricular tachycardia if an influence of the atrial antitachycardia pacing on the ventricular rhythm was determined; otherwise classifying the ventricular rhythm as representing a ventricular tachycardia.

2. Implantable medical device according to claim 1 , characterized in that the computer-readable program causes the processor (32) to inhibit a provision of a ventricular antitachycardia pacing with the stimulation unit (34) and the second electrode (9) if the ventricular rhythm is classified as representing a supraventricular tachycardia.

3. Implantable medical device according to claim 1 or 2, characterized in that the computer- readable program causes the processor (32) to provide a ventricular antitachycardia pacing with the stimulation unit (34) and the second electrode (9) if the ventricular rhythm is classified as representing a ventricular tachycardia.

4. Implantable medical device according to claim 3, characterized in that the computer-readable program causes the processor (32) to provide a predeterminable first amount of ventricular antitachycardia pacings, to repeat steps a) to d), and to provide a predeterminable second amount of ventricular antitachycardia pacings if the ventricular rhythm is classified as representing a ventricular tachycardia in repeated step d).23.086P-WO / 09.03.20265. Implantable medical device according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to provide the atrial antitachycardia pacing during a predeterminable first period of time.

6. Implantable medical device according to claim 5, characterized in that the predeterminable first period of time covers 5 to 20 mean R-R intervals of the ventricular rhythm before providing the atrial antitachycardia pacing.

7. Implantable medical device according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to determine an atrial rhythm with the detection unit (31) and the first electrode (5), to compare the atrial rhythm with the ventricular rhythm and to perform steps b) to d) only if a 1 : 1 relation between the atrial rhythm and the ventricular rhythm is identified upon comparing the atrial rhythm with the ventricular rhythm.

8. Implantable medical device according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to determine an influence of the atrial antitachycardia pacing on the ventricular rhythm by assessing whether at least one of the following conditions is fulfilled:i) first condition: the rate of the ventricular rhythm directly after the atrial antitachycardia pacing still lies above the first predeterminable threshold;ii) second condition: a 1:1 relation between atrial electric signals and ventricular electric signals can be confirmed;iii) third condition: a change of the rate of the ventricular rhythm during the atrial antitachycardia pacing exceeds a second predeterminable threshold;iv) fourth condition: a stability of the ventricular rhythm has decreased during the atrial antitachycardia pacing;classifying the ventricular rhythm as representing a supraventricular tachycardia if i) the first condition is not fulfilled or ii) the first condition is fulfilled and the second condition is fulfilled and at least one of the third and fourth condition is fulfilled; and classifying the ventricular rhythm as representing a ventricular tachycardia in all other cases.

9. Implantable medical device according to claim 8, characterized in that the computer-readable program causes the processor (32) to assess a fulfillment of the second condition only if the first condition is fulfilled, and to assess a fulfillment of at least one of the third condition and the fourth condition only if the second condition is fulfilled.23.086P-WO / 09.03.202610. Implantable medical device according to claim 9, characterized in that the computer-readable program causes the processor (32) to assess a fulfillment of the third condition or the fourth condition only if the respective other of the third condition and the fourth condition is not fulfilled.

11. Implantable medical device according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to compare a morphology of a QRS complex observed in a far-field electrogram i) directly before provision of the atrial antitachycardia pacing and ii) during provision of the atrial antitachycardia pacing to determine an influence of the atrial antitachycardia pacing on the ventricular rhythm.

12. Implantable medical device according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to identify ventricular events during the atrial antitachycardia pacing from a far-field electrogram.

13. Implantable medical device according to any of the preceding claims, characterized in that the implantable medical device comprises a third electrode for detecting left ventricular electric signals or electric signals of a conduction system of the heart, wherein the computer- readable program causes the processor (32) to identify ventricular events during the atrial antitachycardia pacing with the third electrode.

14. Method for operating an implantable medical device (1) for stimulating a human or animal heart, in particular an implantable medical device (1) according to any of the preceding claims, the method comprising the following steps:a) determining a ventricular rhythm with a detection unit (31) and a second electrode (9) and determining a rate of the ventricular rhythm;b) if the rate of the ventricular rhythm exceeds a first predeterminable threshold and is thus indicative for a ventricular tachycardia, triggering an atrial antitachycardia pacing; c) determining an influence of the atrial antitachycardia pacing on the ventricular rhythm;andd) classifying the ventricular rhythm as representing a supraventricular tachycardia if an influence of the atrial antitachycardia pacing on the ventricular rhythm was determined; otherwise classifying the ventricular rhythm as representing a ventricular tachycardia.

15. Method for discriminating between a ventricular tachycardia and a supraventricular tachycardia of a heart of a patient in need of such discrimination, the method being carried out23.086P-WO / 09.03.2026with an implantable medical device (1) for stimulating a human or animal heart, in particular an implantable medical device (1) according to any of claims 1 to 13, the method comprising the following steps:a) determining a ventricular rhythm of the patient’s heart with a detection unit (31) and a second electrode (9) and determining a rate of the ventricular rhythm;b) if the rate of the ventricular rhythm exceeds a first predeterminable threshold and is thus indicative for a ventricular tachycardia, providing an atrial antitachycardia pacing with a stimulation unit (34) and a first electrode (5) to an atrium of the patient’s heart; c) determining an influence of the atrial antitachycardia pacing on the ventricular rhythm;andd) classifying the ventricular rhythm as representing a supraventricular tachycardia if an influence of the atrial antitachycardia pacing on the ventricular rhythm was determined; otherwise classifying the ventricular rhythm as representing a ventricular tachycardia.23.086P-WO / 09.03.2026

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