Implantable medical device having an increased efficacy of an antitachycardia pacing

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 with a detection unit (31) and a ventricular electrode (5) and determining an interval length (VTCL) of at least one cardiac interval of the ventricular rhythm; and b) setting, in dependence on the determined interval length (VTCL), at least one parameter of an antitachycardia stimulation to be delivered by the implantable medical device, wherein the at least one parameter is chosen from a coupling interval, a stimulation interval, a number of stimuli to be applied, and a number of pulse packages to be applied.

Description

[0001] Applicant: BIOTRONIK SE & Co. KG

[0002] Date: 16.03.2026

[0003] Our Reference: 24.039P-WO

[0004] IMPLANTABLE MEDICAL DEVICE HAVING AN INCREASED EFFICACY OF AN ANTITACHYCARDIA PACING

[0005] The present invention relates to an implantable medical device according to the preamble of claim 1, to a cardiac stimulation assembly comprising such an implantable medical device according to the preamble of claim 11, 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.

[0009] However, the efficiency of an antitachycardia stimulation or pacing depends on many factors and has, in prior art defibrillation systems, not yet achieved its optimum. Rather, there remains a need for further optimization of an antitachycardia pacing.It is an object of the present invention to provide an implantable medical device that enables, during its operation, an antitachycardia pacing (ATP) having a higher efficiency than an ATP provided by prior art devices.

[0010] This object is achieved with an implantable medical device having the features of 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 ventricular electrode for detecting ventricular electric signals and for providing stimulation pulses to a ventricle of the heart. Thus, the ventricular electrode forms part of the detection unit and of the stimulation unit.

[0011] 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.

[0012] In a first step (step a)), a ventricular rhythm is determined with the detection unit and the ventricular electrode. In addition, an interval length (also referred to as cycle length) of at least one cardiac interval of the ventricular rhythm is determined.

[0013] In a second step (step b)), at least one parameter of an antitachycardia stimulation to be delivered by the implantable medical device is set. This setting takes place dynamically depending on the determined interval length. In this context, the at least one parameter is chosen from a coupling interval (also referred to as R-Sl interval), a stimulation interval (e.g., an Sl-Sl interval, an S1-S2 interval, an S2-S3 interval, etc.), a number of stimuli to be applied (e.g. during the whole ATP or parts thereof such as a burst of the ATP), and a number of pulse packages to be applied (also referred to as number of attempts or number of attacks of the ATP).

[0014] Due to the dependency of the at least one parameter on the determined interval length, the efficacy and efficiency of the ATP applied by the implantable medical device is significantly increased compared to prior art implantable medical devices that apply a fixed absolute value for the coupling interval and / or the stimulation interval or a fixed relative value of a determined interval length such as a percentage specification featuring a fixed standard value being independent on the factual interval length of the tachycardia rhythm. Thus, the dynamically adjusted parameter used according to an aspect of the presently claimed invention results in a significant improvement of the therapy

[0015] 24.039P-WO / 16.03.2026success of the ATP provided by the implantable medical device according to the presently claimed invention.

[0016] The coupling interval (or R-Sl interval) is that stimulation interval that directly follows the last detected intrinsic R wave of the detected (tachycardic) ventricular rhythm. The various stimulation intervals such as the SI -SI, the S1-S2, and the S2-S3 stimulation intervals are intervals between different types of stimulation pulses. Thus, SI, S2, and S3 denote such different types of stimulation pulses. Typically, 3 to 10, in particular 4 to 9, in particular 5 to 8, in particular 6 to 7, SI pulses are delivered in a so-called burst, wherein the individual SI pulses are delivered in an SI -SI stimulation distance (or SI -SI stimulation interval). Subsequently, S2 and / or aS3 pulses can be delivered by the implantable medical device. However, such delivery of S2 and S3 pulses is generally optional. The S2 and S3 pulses do not count to the burst in its proper sense.

[0017] In an embodiment, the computer-readable program causes the processor to perform the additional step explained in the following after step b). In this additional step (step c)), the stimulation unit is caused to deliver an antitachycardia stimulation (ATP) by applying the at least one parameter set in step b). In an embodiment, this ATP comprises at least one burst comprising 3 to 10, in particular 4 to 9, in particular 5 to 8, in particular 6 to 7, SI pulses. A burst with 5 to 8 SI pulses is particular appropriate. In an embodiment, the ATP comprises more than one burst, in particular 2 to 11, in particular 3 to 10, in particular 4 to 9, in particular 5 to 8, in particular 6 to 7 bursts. In an embodiment, the ATP additionally comprises at least one SI and / or at least one S3 pulse, e.g., one S2 and one S3 pulse.

[0018] In an embodiment, the dependency of the at least one parameter on the determined interval length is realized in form of a factor by which the determined interval length is to be multiplied, wherein the factor depends on the determined interval length.

[0019] In an embodiment, the dependency of the at least one parameter on the determined interval length is realized in form of an absolute value that is assigned to the at least one parameter, wherein the absolute value depends on the determined interval length.

[0020] In an embodiment, the computer-readable program causes the processor to set the parameter by applying a polynomial function, an at least section-wise linear function (such as a step function), or by using a lookup table. In either case, the dependency of the at least one parameter on the determined

[0021] 24.039P-WO / 16.03.2026interval length is decisive for the set value of the at least one parameter. Thus, the function of the lookup table serves as tool for implementing the dependency into practice.

[0022] In an embodiment, the computer-readable program causes the processor to set the parameter by applying a polynomial function or an at least section-wise linear function (such as a step function), wherein at least one coefficient of the polynomial function or of the at least section-wise linear function depends itself on the determined interval length of the ventricular rhythm in form of a polynomial function, an at least section-wise linear function (such as a step function), or a lookup table. Thus, in this embodiment, a double dependency of the interval length on the determined ventricular rhythm is applied. This double dependency serves for an additional increase of the efficacy and efficiency of the ATP applied by the implantable medical device. It increases the influence of the determined interval length on the at least one parameter to be set during operation of the implantable medical device.

[0023] In an embodiment, the computer-readable program causes the processor to set the parameter by calculating the parameter by the following linear function:

[0024] parameter = a * VTCL + b

[0025] In this context, “parameter” denotes the at least one parameter to be set, a and b are linear functions that depend on the determined interval length, and VTCL denotes the determined interval length (ventricular tachycardia cycle length).

[0026] In the special case b = 0, there is a proportional interrelationship between the parameter and the interval length. The coefficient a can be, e.g., a percentage to be multiplied with the interval length in order to obtain the parameter.

[0027] In the special case a = 0, the at least one parameter differs by an offset b from the determined interval length. Since the offset b itself depends on the interval length, there is still a dependency of the parameter on the interval length.

[0028] In an embodiment, the computer-readable program causes the processor to set the parameter depending on a zone boundary of a tachycardia zone associated to the determined interval length. Such a dependency of the at least one parameter on the zone boundary of the tachycardia zone can also be denoted as indirect dependence of the at least one parameter on the determined interval length.

[0029] 24.039P-WO / 16.03.2026The tachycardia zone represents an area or a section into which the determined interval length falls, and which extends from a lower zone boundary to a higher zone boundary. If the at least one parameter depends on such zone boundary, the specific value of the determined interval length is not directly decisive for the setting of the at least one parameter. Rather, it is the zone boundary of the tachycardia zone into which the determined interval length is classified that determines the value to be set for the at least one parameter.

[0030] In an embodiment, the computer-readable program causes the processor to set the at least one parameter depending on the length of the determined interval length. Such dependence can also be referred to as direct dependence of the at least one parameter on the interval length. Here, the specific values of the determined interval length are decisive for the value to be set for the at least one parameter in the setting step.

[0031] In an embodiment, the computer-readable program causes the processor to set the at least one parameter to a value lying in a range between a predeterminable minimum threshold (or lower threshold) and a predeterminable maximum threshold (or higher threshold). The minimum threshold and the maximum threshold can be, e.g., the lower zone boundary and the upper zone boundary of the tachycardia zone associated to the determined interval length. However, the minimum threshold and the maximum threshold can also be, e.g., values being independent on zone boundaries but rather represent an absolute minimum value and an absolute maximum value of the possible values for the at least one parameter.

[0032] In an embodiment, the at least one parameter depends both on the lower zone boundary and the upper zone boundary of the tachycardia zone associated to the determined interval length. To give an example, a weighted average value of the lower zone boundary and the upper zone boundary is, in an embodiment, an appropriate measure for the dependency of the at least one parameter on the determined interval length.

[0033] In an embodiment, the computer-readable program causes the processor to set the at least one parameter to lower values with increasing determined interval length. Thus, the lower the cardiac rate of the determined ventricular rhythm, the smaller is the coupling interval or the stimulation interval if one of these intervals is chosen as the at least one parameter to be set. Such a shorter coupling interval and / or stimulation interval typically serves for a better efficacy of an applied ATP, in particular in case of decreasing ventricular rates. Likewise, a higher number of stimuli and / or a higher number of pulse packages typically increases the efficacy and efficiency of an ATP delivered

[0034] 24.039P-WO / 16.03.2026by the implantable medical device in case of higher (highly tachycardic) ventricular rates, i.e. shorter interval lengths.

[0035] In an embodiment, the computer-readable program causes the processor to additionally alter the at least one parameter according to at least one predeterminable alteration function. This alteration serves for determining the success of an ATP delivered by the implantable medical device with the altered parameter. In addition, computer-readable program causes the processor to choose that alteration function of the at least one predeterminable alteration function that resulted in the best success of the ATP to subsequently set the at least one parameter in dependence on the determined interval length under additional application of that alteration function. Thus, this embodiment applies an automatic therapy optimization by adjusting the at least one parameter to be set and by choosing that alteration function that turned out to be optimal (or at least the best available) for the success of the delivered ATP. Due to physiologic variations between individual patients, the alteration function to be chosen cannot be determined in advance. Rather, the different possible alteration functions need to be tested for the specific setting, and the usability of the specific alteration function needs to be determined by the achieved outcome of the delivered ATP. Due to this testing of various alteration functions under specific individual settings, a highly patient-specific automatic therapy optimization is made possible in this embodiment.

[0036] In an aspect, the present invention relates to a cardiac stimulation assembly comprising an implantable medical device according to the preceding explanations and a programming device that is operatively coupled to the implantable medical device. In this context, the cardiac stimulation assembly comprises a computer-readable program that causes the cardiac stimulation assembly to perform the steps explained in the following when being executed on the cardiac stimulation assembly.

[0037] In a first step (step al), which is typically carried out after step a) explained above as first step of the method carried out by the implantable medical device), the determined interval length is transferred with a data communication unit of the implantable medical device to the programming device.

[0038] In a subsequent step (step a2)), a factor is determined with the programming device, wherein the factor serves for being multiplied with an initial value of the at least one parameter. The factor depends on the determined interval length. Alternatively, a final value of the at least one parameter is determined with the programming device. The final value also depends on the determined interval length.

[0039] 24.039P-WO / 16.03.2026In a subsequent step (step a3)), the factor or the final value of the at least one parameter is transferred to the implantable medical device. In this context, the implantable medical device receives the factor or the final value of the at least one parameter with its data communication unit.

[0040] Afterwards (step a4)), the step of setting the at least one parameter (i.e., the step explained above as step b) carried out by the implantable medical device) is carried out by either multiplying an initial value with the factor or by setting the at least one parameter to the transferred final value. Thus, the cardiac stimulation assembly serves for an interchange of data between the implantable medical device and the programming device operatively coupled to the implantable medical device, wherein individual steps for setting the at least one parameter to a value that depends on the determined interval length are not performed by the implantable medical device itself, but rather by the programming device. This shifts computational effort from the implantable medical device to the programming device and thus saves battery capacity of the implantable medical device. In addition, it is easier to update the software of the programming device so as to be able to adjust or fine-tune the dependency between the determined interval length and the setting of the at least one parameter. Expressed in other words, by shifting some tasks from the implantable medical device to the programming device, the user has more flexibility regarding the setting of the at least one parameter and can also take into account actual general developments in cardiac pacemaker medicine or actual specific developments of the physiologic condition of the patient to be treated with the implantable medical device of the cardiac stimulation assembly, respectively.

[0041] In an embodiment, the computer-readable program causes the cardiac stimulation assembly to determine the factor or the final value of the at least one parameter in dependence on a zone boundary of the tachycardia zone associated to the determined interval length. This indirect dependence between the factor or the final value of the at least one parameter on the one hand and the determined interval length on the other hand makes it possible to assign one and the same factor to different interval lengths, as long as all lengths belong to the same tachycardia zone and thus have the same zone boundary (e.g., a lower zone boundary, an upper zone boundary, or an optionally weighted average value of the lower and the upper zone boundaries). Reference is made to the explanations given above with respect to the indirect dependence between the at least one parameter and the determined interval length.

[0042] In an embodiment, the computer-readable program causes the cardiac stimulation assembly to determine the factor or the final value of the at least one parameter in dependence on a length of the

[0043] 24.039P-WO / 16.03.2026determined interval length. Thus, in this embodiment, a direct dependence between the factor or the final value of the at least one parameter on the one hand and the determined interval length on the other hand is exploited to set the at least one parameter. Reference is also made to the explanations given above with respect to the implantable medical device and the direct dependence between the at least one parameter and the interval length.

[0044] In 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. This method comprises the steps explained in the following.

[0045] In a first step (step a)), a ventricular rhythm is determined with a detection unit and a ventricular electrode forming part of the detection unit of the implantable medical device. In addition, an interval length of at least one cardiac interval of the ventricular rhythm is determined with the detection unit.

[0046] In another method step (step b)), at least one parameter of an antitachycardia pacing (ATP) to be delivered by the implantable medical device is set. The at least one parameter depends on the determined interval length. In this context, the at least one parameter is chosen from a coupling interval, a stimulation of, a number of stimuli to be applied, and a number of pulse packages to be applied.

[0047] In an aspect, the present invention relates to a medical method for applying an antitachycardia therapy with an implantable medical device for stimulating a human or animal heart, in particular an implantable medical device according to any of the above explanations, to a patient in need of such therapy. The method comprises the steps explained in the following.

[0048] In a first step (step a)), a ventricular rhythm is determined with a detection unit and a ventricular electrode forming part of the detection unit of the implantable medical device. In addition, an interval length of at least one cardiac interval of the ventricular rhythm is determined with the detection unit.

[0049] In another method step (step b)), at least one parameter of an antitachycardia pacing (ATP) to be delivered by the implantable medical device is set. The at least one parameter depends on the determined interval length. In this context, the at least one parameter is chosen from a coupling interval, a stimulation of, a number of stimuli to be applied, and a number of pulse packages to be applied.

[0050] 24.039P-WO / 16.03.2026In another method step (step c)), a stimulation unit of the implantable medical device is caused to deliver an ATP to the patient's heart by applying the at least one parameter set in step b). Thus, the implantable medical device delivers an ATP with at least one stimulation parameter that is adapted in dependence on the previously determined interval length and is thus specifically adjusted to the patient's need and the specificities of the ventricular rhythm to be treated with the ATP.

[0051] 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 cardiac stimulation assembly and to the described methods. Likewise, all embodiments of the described cardiac stimulation assembly can be combined in any desired way and can be transferred either individually or in any arbitrary combination to the implantable medical device and to the methods. Finally, all embodiments of each 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, to the cardiac stimulation assembly, and to the respective other method.

[0052] 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:

[0053] Figure 1A schematically shows a cardiac stimulation assembly comprising an implantable medical device;

[0054] Figure IB schematically shows different components of the implantable medical device of Figure 1 A;

[0055] Figure 2A shows a graph illustrating the dependency of the relative length of the R-Sl interval or the S 1 -S 1 interval on the determined interval length of the ventricular rhythm; and

[0056] Figure 2B shows a graph illustrating the dependency of the relative length of the R-Sl interval or the SI -SI interval on the determined interval length of the ventricular rhythm.

[0057] 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. The ICD device 1 and the programming device 2 together form a cardiac stimulation assembly 12.

[0058] 24.039P-WO / 16.03.2026The ICD device 1 comprises a housing 3 with a header 4 and a ventricular electrode 5 connected to the header 4. The ventricular electrode 5 comprises a tip electrode pole 6 and a ring electrode pole 7 that is proximally arranged from the tip electrode pole 6. Electric cardiac signals sensed between the tip electrode pole 6 and the ring electrode pole 7 are directly recorded within a heart chamber, typically the right ventricle. Thus, the first electrode 5 is designed and arranged to sense right ventricular electric signals.

[0059] 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 ventricular electrode 5 along with its tip electrode pole 6 and ring electrode pole 7 (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 1A).

[0060] Figure 2A illustrates an embodiment of an optimized adjustment of a zone-specific relative length of a coupling interval (R-Sl interval) or of a stimulation interval (SI -SI interval), respectively. The relative length of the coupling interval or the stimulation interval, respectively, decreases stepwise (i.e., according to a section-wise linear function) with increasing interval length VTCL. A high or long interval length corresponds to a slower ventricular rhythm, i.e., to a less pronounced tachycardia. To give an example, any interval length VTCL lying in a range between approximately 320 ms and 400 ms is assigned to the same tachycardia zone having an upper zone boundary of approximately 320 ms and a lower zone boundary of approximately 400 ms. All interval lengths assigned to this tachycardia zone result in a relative length of the coupling interval or the stimulation interval, respectively, of approximately 0.75. Thus, the coupling interval length or the stimulation interval length, respectively, corresponds to 75 % of the determined interval length. If, however, the determined interval length VTCL falls in a range, e.g., from approximately 500 ms to approximately 550 ms, an associated relative length of the coupling interval or of the stimulation interval,

[0061] 24.039P-WO / 16.03.2026respectively, of approximately 0.6 is assigned to the respective interval length (the corresponding tachycardia zone ranges from 500 ms to 550 ms as zone boundaries). Thus, in such a case of a comparatively longer determined interval length, the length of the coupling interval or of the stimulation interval, respectively, amounts to only 60 % of the determined interval length. In any case, the length of the applied coupling interval or of the applied stimulation interval, respectively, depends on the determined interval length. Since different interval lengths assigned to the same tachycardia zone result in the same relative length of the coupling interval or of the stimulation interval, respectively, there is an indirect dependency of the coupling interval length or of the stimulation interval length, respectively, on the determined interval length VTCL.

[0062] A straight line 11 illustrates a direct dependency between the relative length of the coupling interval or of the stimulation interval, respectively, and the determined interval length VTCL in an area ranging from approximately 270 ms to approximately 630 ms. Here, individual interval lengths determined by the detection unit of the implantable medical device will result in individual relative lengths of the coupling interval or of the stimulation interval, respectively.

[0063] Figure 2B shows a similar graph like Figure 2A. However, the on the x-axis, not the interval length VTCL, but rather the ventricular rhythm or cardiac rhythm CR is plotted. Since the cardiac rhythm CR is the inverse value of the interval length VTCL, the mathematic relationship between the relative length of the coupling interval or of the stimulation interval, respectively, and the cardiac rhythm CR is simply inverse to the relationship between the relative length of the coupling interval or of the stimulation interval, respectively, and the interval length VTCL, as illustrated in Figure 2A. I.e., the relative length of the coupling interval or of the stimulation interval, respectively, increases with increasing cardiac rhythm CR. But also in case of Figure 2B, the relationship between the relative length of the coupling interval or of the stimulation interval, respectively, and the cardiac rhythm CR corresponds to a section-wise linear function, namely, to a function illustrating different tachycardia zones assigned to specific ranges of the cardiac rhythm.

[0064] In practice, a user of an ICD can set an optimized coupling interval or stimulation interval, respectively, by choosing the corresponding parameter in the options menu of the adjustment software to the value "AUTO". In such a case, various implementations are possible, two of which will be explained in the following in more detail.

[0065] According to a first implementation, the programming device 2 calculates from the average value between the lower and the upper zone boundary of the relevant tachycardia zone into which a

[0066] 24.039P-WO / 16.03.2026determined interval length is classified the optimum relative length of the coupling interval or of the stimulation interval, respectively, to be adjusted. This optimum relative length is then sent to the ICD device 1 operatively coupled to the programming device 2. In this context, the coupling interval or the stimulation interval, respectively, can only be adjusted in a range from 0.65 to 0.90 (corresponding to 65 % to 90 %) of the interval length, in particular in a range from 0.70 to 0.85, in particular in a range from 0.75 to 0.80.

[0067] In a second implementation, the ICD device 1 uses the determined interval length for calculating the relative length of the coupling interval or the stimulation interval, respectively, to be used, wherein this calculation is performed by the firmware installed within the ICD device 1. Also in this case, the relative length can only be adjusted within a range from 0.65 to 0.90 (corresponding to 65 % to 90 %) of the interval length, in particular in a range from 0.70 to 0.85, in particular in a range from 0.75 to 0.80.

[0068] 24.039P-WO / 16.03.2026

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, and a ventricular electrode (5) 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 ventricular electrode (5) and determining an interval length (VTCL) of at least one cardiac interval of the ventricular rhythm; andb) setting, in dependence on the determined interval length (VTCL), at least one parameter of an antitachycardia stimulation to be delivered by the implantable medical device, wherein the at least one parameter is chosen from a coupling interval, a stimulation interval, a number of stimuli to be applied, and a number of pulse packages to be applied.

2. Implantable medical device (1) according to claim 1, characterized in that the computer- readable program causes the processor (32) to perform the following step after step b):c) causing the stimulation unit to deliver an antitachycardia stimulation by applying the at least one parameter set in step b).

3. Implantable medical device (1) according to claim 1 or 2, characterized in that the computer- readable program causes the processor (32) to set the at least one parameter by applying a polynomial function or an at least section-wise linear function, or by using a lookup table.

4. Implantable medical device (1) according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to set the at least one parameter24.039P-WO / 16.03.2026by applying a polynomial function or an at least section-wise linear function, wherein at least one coefficient of the polynomial function or the at least section-wise linear function itself depends on the determined interval length (VTCL) in form of a polynomial function, an at least section-wise linear function, or a lookup table.

5. Implantable medical device (1) according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to set the at least one parameter by calculating the at least one parameter by the following linear function:parameter = a * VTCL + bwherein a and b are linear functions that depend on the determined interval length (VTCL).

6. Implantable medical device (1) according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to set the at least one parameter in dependence on a zone boundary of a tachycardia zone associated to the determined interval length (VTCL).

7. Implantable medical device (1) according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to set the at least one parameter in dependence on a length of the determined interval length (VTCL).

8. Implantable medical device (1) according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to set the at least one parameter to a value lying in a range between a predeterminable minimum threshold and a predeterminable maximum threshold.

9. Implantable medical device (1) according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to set the at least one parameter to lower values with increasing determined interval length (VTCL).

10. Implantable medical device (1) according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to additionally alter the at least one parameter according to at least one predeterminable alteration function, to determine a success of an antitachycardia stimulation applied by the implantable medical device (1) with24.039P-WO / 16.03.2026the altered parameter, and to choose that alteration function of the at least one predeterminable alteration function that resulted in the best success of the antitachycardia stimulation to subsequently set the at least one parameter in dependence on the determined interval length (VTCL) under additional application of that alteration function.

11. Cardiac stimulation assembly (12) comprising an implantable medical device (1) according to any of the preceding claims and a programming device (2) operatively coupled to the implantable medical device (1), wherein the cardiac stimulation assembly (12) comprises a computer-readable program that causes the cardiac stimulation assembly (12) to perform the following steps when being executed on the cardiac stimulation assembly (12):al) transferring, with a data communication unit (36) of the implantable medical device (1), the determined interval length (VTCL) to the programming device (2);a2) determining, with the programming device (2) and depending on the determined interval length (VTCL), i) a factor by which an initial value of the at least one parameter is to be multiplied or ii) a final value of the at least one parameter;a3) transferring the factor or the final value of the at least one parameter to the implantable medical device (1); anda4) carrying out the step of setting the at least one parameter i) by multiplying an initial value with the factor or ii) by setting the at least one parameter to the final value of the at least one parameter.

12. Cardiac stimulation assembly (12) according to claim 11, characterized in that the computer- readable program causes the cardiac stimulation assembly (12) to determine the factor or the final value of the at least one parameter in dependence on a zone boundary of a tachycardia zone associated to the determined interval length (VTCL).

13. Cardiac stimulation assembly (12) according to claim 11 or 12, characterized in that the computer-readable program causes the cardiac stimulation assembly (12) to determine the factor or the final value of the at least one parameter in dependence on a length of the determined interval length (VTCL).24.039P-WO / 16.03.202614. 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 claimSl to 10, the method comprising the following steps:a) determining a ventricular rhythm with a detection unit (31) and a ventricular electrode (5) of the implantable medical device (1) and determining an interval length (VTCL) of at least one cardiac interval of the ventricular rhythm; andb) setting, in dependence on the determined interval length (VTCL), at least one parameter of an antitachycardia stimulation to be delivered by the implantable medical device, wherein the at least one parameter is chosen from a coupling interval, a stimulation interval, a number of stimuli to be applied, and a number of pulse packages to be applied.

15. Method for applying an antitachycardia therapy with an implantable medical device (1) for stimulating a human or animal heart, in particular an implantable medical device (1) according to any of claimSl to 10, to a patient in need of such therapy, the method comprising the following steps:a) determining a ventricular rhythm with a detection unit (31) and a ventricular electrode (5) of the implantable medical device (1) and determining an interval length (VTCL) of at least one cardiac interval of the ventricular rhythm;b) setting, in dependence on the determined interval length (VTCL), at least one parameter of an antitachycardia stimulation to be delivered by the implantable medical device, wherein the at least one parameter is chosen from a coupling interval, a stimulation interval, a number of stimuli to be applied, and a number of pulse packages to be applied; andc) causing a stimulation unit of the implantable medical device (1) to deliver an antitachycardia stimulation to the patient’s heart by applying the at least one parameter set in step b).24.039P-WO / 16.03.2026

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