Implantable medical device enabling a temporary modification of a timing parameter

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 if a scheduled left ventricular pacing pulse (LVp) can be delivered with a second electrode (9), wherein a delivery of the left ventricular pacing pulse (LVp) is subject to an expiration of a presettable protective interval (LVURI) that is initiated by a preceding left ventricular pacing pulse (LVp) delivered with the second electrode (9), a preceding left ventricular depolarization (LVs) detected with the second electrode (9), or a preceding logic event (LVp(PH)) triggered instead of a preceding left ventricular pacing pulse (LVp) at the same time at which the preceding left ventricular pacing pulse (LVp) was scheduled to be delivered; and b) if the left ventricular pacing pulse (LVp) cannot be delivered since the presettable protective interval (LVURI) is not yet expired, adjusting at least one timing parameter of the implantable medical device (1) such that a subsequent left ventricular pacing pulse (LVp) is scheduled to be delivered after expiration of a respective subsequent presettable protective interval (LVURI).

Description

[0001] Applicant: BIOTRONIK SE & Co. KG

[0002] Date: 02.03.2026

[0003] Our Reference: 22.270P-WO

[0004] Implantable medical device enabling a temporary modification of a timing parameter

[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 for cardiac resynchronization therapy (CRT) in which they apply stimulation pulses to a de-synchronized heart in order to resynchronize the heart again.

[0008] In pacemaker modes with programmed biventricular or left ventricular pacing a situation can occur (e. g., by an atrial or a ventricular extrasystole or by a change of timing parameters of the pacing program) that leads to an inhibition of the delivery of a left ventricular pace. If due to the missing pace an occurring left ventricular depolarization (i.e., a left ventricular sense event, LVs) retriggers a protective interval, then the next left ventricular pace delivery can be inhibited again and so on. A so-called lock-in situation is generated. This phenomenon is also described, e.g., by Barold and Kucher (Barold, S. Serge, and Andreas Kucher. “Interruption of cardiac re synchronization therapy by atrial premature complexes.” Journal of Electrocardiology 51.2 (2018): 247-251).

[0009] Prior art pacemakers employing CRT pursue different strategies to avoid such a lock-in situation. Some of the prior art pacemakers do not enable the retriggering of the protective interval by left ventricular sense events. However, this reduces the medical safety of such CRT devices irrespective of the cardiac rhythm of the patient. If, e.g., the parameter “LV T-wave protection” (that prevents a left ventricular stimulation during the T wave which could lead to ventricular fibrillation) is turned off permanently there is an increased risk of left ventricular pacing into the vulnerable phase of the left ventricle. This can have severe side effects for the patient.It is an object of the present invention to provide a device for cardiac re synchronization therapy that enables safe cardiac resynchronization therapy also in case of an irregular cardiac rate and avoids pacing situations that increase the risk of cardiac fibrillation.

[0010] 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 detection unit comprises a first electrode for detecting right ventricular electric signals and a second electrode for detecting left ventricular electric signals.

[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, it is determined if a left ventricular pacing pulse can be delivered with the second electrode. This delivery is subject to a condition. According to this condition, a presettable protective interval needs to be expired. This presettable protective interval has two functions. First, it defines a maximum left ventricular pacing rate. Under this aspect, the presettable protective interval is utilized to prevent sensible patients from experiencing palpitations at elevated resynchronization rates. Second, since the present implantable medical device is capable of left ventricular sensing, the presettable protective interval serves as a protection against competitive left ventricular pacing after detected left ventricular senses. Expressed in other words, the presettable protective interval allows the delivery of a left ventricular pacing pulse only if the left ventricle is in a physiologic state in which a contraction would occur under natural conditions. The presettable protective interval is initiated by one of three possible events. The first event is a preceding left ventricular pacing pulse delivered with the second electrode. The second event is a preceding left ventricular depolarization detected with the second electrode. The third event is a preceding logic event that is triggered instead of a preceding left ventricular pacing pulse at the same time at which the preceding left ventricular pacing pulse was scheduled to be delivered. Such a logic event can also be denoted as phantom pace or phantom pacing pulse. It replaces a real pacing pulse in case that the conditions for delivering the real pacing pulse are not met (e.g., because of a non-terminated presettable protective interval). In this context, “preceding” refers to an event that directly or indirectly precedes the left ventricular pacing pulse that was scheduled to be delivered (but being subject to the conditions to be met).

[0013] 22.270P-WO / 02.03.2026If the left ventricular pacing pulse scheduled to be delivered cannot be delivered since the presettable protective interval is not yet expired, at least one timing parameter of the implantable medical device is adjusted such that a subsequent left ventricular pacing pulse is scheduled to be delivered after expiration of a respective subsequent presettable protective interval. In this context, “subsequent” refers to an event that directly or indirectly succeeds the left ventricular pacing pulse that was scheduled to be delivered (but being subject to the condition to be met). This will enable the delivery of a following left ventricular pacing pulse aiming in a cardiac resynchronization even in case that a right ventricular extrasystole or a left ventricular extrasystole has occurred that resulted in a cardiac de -synchronization and a premature start of the presettable protective interval.

[0014] By adjusting the at least one timing parameter of the implantable medical device in one or more subsequent cardiac intervals, a cardiac re synchronization can be restored immediately after the synchronizing event. This increases the general CRT success. Furthermore, it helps to reduce the number of the synchronization episodes after the detection of CRT interrupt. At the same time, the permanent LV T-wave protection remains fully active. Moreover, a time period in which a patient may experience palpitations due to a reduced protective interval is minimized. The probability of an occurrence of a so-called lock-in situation due to premature restarts of the presettable protective interval increases with increasing cardiac rates and, in the prior art, will only be resolved if the cardiac rate decreases. The present invention thus especially increases the general CRT success at higher cardiac rates.

[0015] Prior art CRT devices currently record intracardiac electrogram (IEGM) episodes of the type “end of CRT pacing”. Patients having an irregular cardiac rate generate a plurality of such IEGM episodes (partly even everyday) that are entered into a log file or that are sent to a remote service center. These IEGM episodes are even generated if a statistic evaluation shows almost 100 % CRT pacing per day. Expressed in other words, these IEGM episodes result from an undesired temporal interruption of CRT due to the lacking possibility of a fast resynchronization of the heartbeat. It would generally be desirable to reduce the number of such IEGM episodes to a minimum to clearly identify critical IEGM episodes or to not store or present rather uncritical IEGM episodes representing a (short) interruption of CRT. By enabling fast re synchronization after a de-synchronizing event due to an adjustment of the at least one timing parameter of the implantable medical device, the number of such IEGM episodes can be significantly reduced, wherein only IEGM episodes that could not be resolved by the adjustment of the at least one timing parameter of the implantable medical device would be recorded at all. This reduces the amount of physiologically irrelevant IEGM episodes and allows an easy identification of relevant IEGM episodes that require separate or additional therapy.

[0016] 22.270P-WO / 02.03.2026The at least one timing parameter to be adjusted is a timing parameter that influences the scheduled delivery of a left ventricular pacing pulse. In an embodiment, exactly one timing parameter is adjusted.

[0017] In an embodiment, the at least one timing parameter is a pacing interval (PI, AA). The pacing interval defines the distance between two adjacent atrial or two adjacent ventricular pacing pulses.

[0018] In an embodiment, the at least one timing parameter is an upper rate interval (also referred to as upper tracking interval, UTI). The upper rate defines an upper pacing rate for ventricular pacing which should not be exceeded. Accordingly, the upper rate interval defines a time interval which is started at the time a (leading) ventricular pace is scheduled, i.e. in a two-chamber stimulation system upon termination of a first atrioventricular interval (AV) and terminates before a directly succeeding ventricular pace is scheduled. The upper rate interval typically terminates prior to the expiration of the second atrioventricular interval.

[0019] In an embodiment, the at least one timing parameter is an atrioventricular interval (AV). The atrioventricular interval defines the time period between an atrial sensing or pacing event and the directly subsequent ventricular pacing event. It reflects the physiologic atrioventricular conduction time.

[0020] In an embodiment, the at least one timing parameter is an interventricular delay after pace (VVp). The interventricular delay after pace reflects the waiting time between a pacing event in one of the two ventricles and a directly subsequent pacing event in the respective other ventricle. The first paced ventricle can be the right ventricle or the left ventricle.

[0021] In an embodiment, adjusting the at least one timing parameter involves temporarily extending (prolonging) the pacing interval. In an embodiment, adjusting the at least one timing parameter involves, temporarily extending (prolonging) the upper rate interval. In an embodiment, adjusting the at least one timing parameter involves temporarily extending (prolonging) the atrioventricular interval. In an embodiment, adjusting the at least one timing parameter involves temporarily extending (prolonging) or temporarily reducing the interventricular delay after pace. Any of these measures is appropriate to open a time window in which a left ventricular pace can be delivered without and constitute an alternative to permanently deactivating the parameter “LV T-Wave Protection” or permanently reducing the presettable protective interval which typically have negative

[0022] 22.270P-WO / 02.03.2026effects on the well-being of the patient. Thus, any of these measures is appropriate to achieve cardiac resynchronization.

[0023] In an embodiment, adjusting the at least one timing parameter involves temporarily extending the interventricular delay after pace by an extension period lying in a range of from 5 ms to 100 ms, in particular from 10 ms to 90 ms, in particular from 20 ms to 80 ms, in particular from 20 ms to 70 ms, in particular from 30 ms to 60 ms, in particular from 40 ms to 50 ms. The extended interventricular delay after pace should typically not exceed 100 ms.

[0024] In an embodiment, adjusting the at least one timing parameter involves temporarily reducing the interventricular delay after pace (VVp) to a final value lying in a range of from 0 ms to 50 ms, in particular from 5 ms to 45 ms, in particular from 10 ms to 40 ms, in particular from 15 ms to 35 ms, in particular from 20 ms to 30 ms. By reducing the interventricular delay after pace to a final value of 0 ms, pacing pulse can be delivered directly to the second-paced ventricle upon delivering a pacing pulse to the first-paced ventricle. Expressed in other words, setting the interventricular delay after pace to a final value of 0 ms, a concomitant pacing of both ventricles is made possible.

[0025] In an embodiment, the computer-readable program causes the processor to keep presettable protective interval constant. By keeping this parameter constant but amending the at least one timing parameter, a particular appropriate effect of the adjustment of the at least one timing parameter with respect to delivery of a left ventricular pacing pulse and with respect to cardiac resynchronization is achieved.

[0026] The term “temporarily” as used throughout in here refers to an adjustment that is only valid for a certain time period, wherein the original length of the timing parameter is restored afterwards. In an embodiment, the computer-readable program causes the processor to adjust the at least one timing parameter only for a single cardiac cycle or for 2 to 10, in particular 3 consecutive cardiac cycles during a predeterminable time window (such as, e.g, 1 second to 1 minute, in particular 5 seconds to 55 seconds, in particular 10 seconds to 50 seconds, in particular 20 seconds to 40 seconds, in particular 25 seconds to 30 seconds). By limiting the adjustment to only a single cardiac cycle in this predeterminable time window, the time period in which a patient may experience negative side effects on the well-being due to a temporarily adjusted timing parameter is considerably low, in particular in comparison to permanently shortening the presettable protective time interval.

[0027] 22.270P-WO / 02.03.2026In an embodiment, the computer readable program causes the processor to detect at least one right ventricular depolarization with the first electrode. In an embodiment, the computer readable program causes the processor to deliver at least one right ventricular pacing pulse with the first electrode.

[0028] In an embodiment, another condition needs to be met for delivering the left ventricular pacing pulse. According to this additional condition, a predeterminable interventricular interval (representing the regular delay of contraction of the left ventricle in relation to a contraction of the right ventricle) needs to be expired. This interventricular interval is typically rather short since both the right ventricle and the left ventricle depolarize quite simultaneously.

[0029] In an embodiment, the computer-readable program causes the processor to repeat the step of determining if a left ventricular pacing pulse can be delivered and the step of adjusting the at least one timing parameter in 1 to 6, in particular 2 to 5, in particular 3 to 4 subsequent cardiac cycles. This facilitates re-establishing resynchronization of the heart, e.g., during a phase in which the ventricular rate would otherwise inhibit a scheduled left ventricular pacing pulse due to a premature start of the presettable protective interval and / or an overlap of two or more presettable protective intervals that result in an extended period of time during which left ventricular pacing pulses are inhibited. However, one should bear in mind that a repetition of the individual method steps might increase the risk of deteriorating the well-being of the patient by non-optimal parameter settings. Therefore, the repetition should not exceed the above-mentioned number.

[0030] In an embodiment, the computer-readable program causes the processor to determine if reestablishing cardiac resynchronization has been successful. In case that no cardiac re synchronization could yet be obtained, the step of determining if a left ventricular pacing pulse can be delivered (upon fulfilment of the above-mentioned condition) and the step of adjusting the at least one timing parameter are repeated after a predeterminable first time period or upon a reduction of the current heart rate. The predeterminable first time period represents a pause in the applied intervention for attempting re-establishing cardiac synchronization.

[0031] In an embodiment, the first time period lies in a range of from 30 seconds to 5 minutes, in particular from 45 seconds to 4 minutes, in particular from 1 minute to 3.5 minutes, in particular from 1.5 minutes to 3 minutes, in particular from 2 minutes to 2.5 minutes. The alternative trigger for repeating the individual method steps, i.e., a reduction of the current heart rate, is, in an embodiment, a reduction of the current heart rate by at least 10 bpm, in particular at least 15 bpm, in particular at least 20 bpm, in particular at least 25 bpm, in particular at least 30 bpm. In an embodiment, the

[0032] 22.270P-WO / 02.03.2026reduction of the current heart rate is a reduction lying in a range of from 10 bpm to 55 bpm, in particular from 15 bpm to 50 bpm, in particular from 20 bpm to 45 bpm, in particular from 25 bpm to 40 bpm, in particular from 30 bpm to 35 bpm.

[0033] In an embodiment, the computer-readable program causes the processor to perform the step of determining if a left ventricular pacing pulse can be delivered (upon fulfilment of the above-mentioned condition), and the step of reducing the next or one or more presettable protective intervals only 1 to 6 times, in particular only 2 to 5 times, in particular only 3 to 4 times per predeterminable time window ranging from 6 minutes to 1 hour, in particular from 10 minutes to 55 minutes, in particular from 15 minutes to 50 minutes, in particular from 20 minutes to 45 minutes, in particular from 25 minutes to 40 minutes, in particular from 30 minutes to 35 minutes. By applying such a limitation of attempts for achieving resynchronization of the heart over a specific time window, the risk that the applied intervention interferes with the health status of the patient is significantly reduced. Thus, a limitation of attempts over the specified time window represents a good compromise between attempting to achieve a resynchronization of the heart and reducing the risk of deteriorating a therapy success by not optimally set timing parameters.

[0034] In an embodiment, the computer-readable program causes the processor to perform the step of adjusting the at least one timing parameter only if at least 2, in particular at least 3, in particular at least 4, in particular at least 5, in particular at least 6, in particular at least 7, in particular at least 8, in particular at least 9, in particular at least 10, in particular exactly 2, 3, 4, 5, 6, 7, 8, 9 or 10, consecutive scheduled left ventricular pacing pulses cannot be delivered for reason that the respective presettable protective intervals have not been expired prior to the scheduled pulse delivery. By increasing the number of consecutive scheduled left ventricular pacing pulses, the delivery of which could not take place, the sensitivity of the applied algorithm is reduced so that the attempt of applying a cardiac resynchronization is only performed in case of a persisting cardiac de -synchronization. This will allow additional time for the heart to return to its physiologic synchronized periodic beating pattern without external intervention (i.e., without applying the left ventricular pacing pulse). This increases the physiologic compatibility of the implantable medical device and its functionality.

[0035] In an embodiment, the computer-readable program causes the processor to disable the step of adjusting the at least one timing parameter for a predeterminable second time period if cardiac resynchronization has not been successful during a third time period. In this context, the third time period occurs earlier than the second time period. Disabling the step of adjusting the at least one timing parameter is a safety measure to avoid the consecutive attempt of application

[0036] 22.270P-WO / 02.03.2026resynchronization therapy to the patient if the patient is not susceptible to such therapy. In such a case, it is more convenient to disable the functionality and to enable it again only after a follow-up examination of the patient by a physician or after the expiration of a specific time period during which the physiologic state of the patient’s heart can have changed so that the heart becomes (again) more susceptible to the re synchronization therapy to be applied.

[0037] In an embodiment, an unsuccessful cardiac resynchronization is assumed if N attempts for establishing cardiac resynchronization by reducing the presettable protective interval during the third time period did not result in cardiac resynchronization. In this context, N is a number lying in a range of from 20 to 1500, in particular from 30 to 1400, in particular from 40 to 1300, in particular from 50 to 1200, in particular from 60 to 1100, in particular from 75 to 1000, in particular from 90 to 900, in particular from 100 to 800, in particular from 200 to 700, in particular from 300 to 600, in particular from 400 to 500.

[0038] In an embodiment, the third time period lies in a range of from 6 hours to 24 hours, in particular from 7 hours to 23 hours, in particular from 8 hours to 22 hours, in particular from 9 hours to 21 hours, in particular from 10 hours to 20 hours, in particular from 11 hours to 19 hours, in particular from 12 hours to 18 hours, in particular from 13 hours to 17 hours, in particular from 14 hours to 16 hours, in particular from 15 hours to 15.5 hours.

[0039] In an embodiment, the second time period lies in a range of from 1 to 7 days, in particular from 2 to 6 days, in particular from 3 to 5 days, in particular from 4 to 4.5 days, or lasts until the next scheduled follow-up examination of the patient.

[0040] In an embodiment, the computer-readable program causes the processor to perform steps a) to b) for a maximum number of 2 to 10, in particular 3 or 5 cardiac cycles and disable step b) for 40 to 60, in particular 48 cardiac cycles upon reaching the maximum number. In another embodiment, the computer-readable program causes the processor to perform steps a) to b) for 10 to 15 cardiac cycles, in particular 12 cardiac cycles within a total number of 40 to 60 cardiac cycles, in particular 48 cardiac cycles and disable step b) for 140 to 180 cardiac cycles, in particular for 160 cardiac cycles.

[0041] In an embodiment, the presettable protective interval has a duration lying in a range of from 275 ms to 700 ms, in particular from 300 ms to 675 ms, in particular from 325 ms to 675 ms, in particular from 350 ms to 650 ms, in particular from 375 ms to 625 ms, in particular from 400 ms to 600 ms, in particular from 425 ms to 575 ms, in particular from 450 ms to 550 ms, in particular from 475 ms

[0042] 22.270P-WO / 02.03.2026to 525 ms or from 275 ms to 400 ms. A duration of the presettable protective interval of 300 ms corresponds to a cardiac rate of 200 bpm. I.e., as long as the cardiac rate is not higher than 200 bpm, than a presettable protective interval of 300 ms will allow the delivery of a left ventricular pacing pulse. A duration of the presettable protective interval of 700 ms corresponds to a cardiac rate of approximately 86 bpm. The intermediate variations of the presettable protective intervals correspond to intermediate cardiac rates. The cardiac rate in beats per minute can be calculated as l / (duration in milliseconds)*60,000. The regular (non-reduced) presettable protective interval typically has a duration in a range from 350 ms to 700 ms, in particular 400 ms to 500 ms or in particular from 550 ms to 675 ms, in particular from 600 ms to 650 ms.

[0043] In an embodiment, the implantable medical device comprises a data communication unit that serves for transferring data to a remote monitoring system in a wireless manner. 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 fifth-generation technology standard for broadband cellular networks (5G).

[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. In this context, the method comprises the steps explained in the following.

[0045] In a first step, it is determined if a left ventricular pacing pulse can be delivered with a second electrode. This delivery is subject to a condition. According to this condition, a presettable protective interval needs to be expired. This presettable protective interval serves for preventing a left ventricular pacing into a vulnerable phase of the left ventricle. The presettable protective interval is initiated by one of three possible events. The first event is a preceding left ventricular pacing pulse delivered with the second electrode. The second event is a preceding left ventricular depolarization detected with the second electrode. The third event is a preceding logic event that is triggered instead of a preceding left ventricular pacing pulse at the same time at which the preceding left ventricular pacing pulse was scheduled to be delivered. Such a logic event can also be denoted as phantom pace or phantom pacing pulse. It replaces a real pacing pulse in case that the conditions for delivering the

[0046] 22.270P-WO / 02.03.2026real pacing pulse are not met (e.g., because of a non-terminated presettable protective interval). In this context, “preceding” refers to an event that directly or indirectly precedes the left ventricular pacing pulse scheduled to be delivered (but being subject to the conditions to be met).

[0047] In a second step, at least one timing parameter of the implantable medical device is adjusted such that a following left ventricular pacing pulse is scheduled to be delivered after expiration of a respective subsequent presettable protective interval, if the left ventricular pacing pulse scheduled to be delivered cannot be delivered since the presettable protective interval is not yet expired. This will enable the delivery of a left ventricular pacing pulse aiming in a cardiac re synchronization even in case that a right ventricular extrasystole or a left ventricular extrasystole has occurred that resulted in a cardiac de-synchronization and a premature start of the presettable protective interval.

[0048] In an aspect, the present invention relates to a method for providing a cardiac resynchronization therapy to a patient in need thereof 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.

[0049] In a first step, it is determined if a left ventricular pacing pulse can be delivered with a second electrode. This delivery is subject to a condition. According to this condition, a presettable protective interval needs to be expired. This presettable protective interval serves for, amongst other things, preventing a left ventricular pacing into a vulnerable phase of the left ventricle. The presettable protective interval is initiated by one of three possible events. The first event is a preceding left ventricular pacing pulse delivered with the second electrode. The second event is a preceding left ventricular depolarization detected with the second electrode. The third event is a preceding logic event that is triggered instead of a preceding left ventricular pacing pulse at the same time at which the preceding left ventricular pacing pulse was scheduled to be delivered. Such a logic event can also be denoted as phantom pace or phantom pacing pulse. It replaces a real pacing pulse in case that the conditions for delivering the real pacing pulse are not met (e.g., because of a non-terminated presettable protective interval). In this context, “preceding” refers to an event that directly or indirectly precedes the left ventricular pacing pulse scheduled to be delivered (but being subject to the conditions to be met).

[0050] In a second step, at least one timing parameter of the implantable medical device is adjusted such that a following left ventricular pacing pulse is scheduled to be delivered after expiration of a respective subsequent presettable protective interval, if the left ventricular pacing pulse scheduled to

[0051] 22.270P-WO / 02.03.2026be delivered cannot be delivered since the presettable protective interval is not yet expired. This will enable the delivery of a left ventricular pacing pulse aiming in a cardiac re synchronization even in case that a right ventricular extrasystole or a left ventricular extrasystole has occurred that resulted in a cardiac de-synchronization and a premature start of the presettable protective interval.

[0052] In a third step, a left ventricular pacing pulse is delivered to the patient after expiration of the respective subsequent presettable protective interval.

[0053] 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 method. Likewise, all embodiments of the described method can be combined in any desired way and can be transferred either individually or in any arbitrary combination to the implantable medical device.

[0054] 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:

[0055] Figure 1A schematically shows a system comprising an implantable medical device according to an embodiment of the present invention;

[0056] Figure IB schematically shows different components of the implantable medical device of Figure 1A;

[0057] Figure 2A schematically shows a system comprising an implantable medical device according to another embodiment of the present invention;

[0058] Figure 2B schematically shows different components of the implantable medical device of Figure 2A;

[0059] Figure 3A shows a first schematic illustration of cardiac events sensed by a prior art CRT device and pacing pulses delivered by this CRT device together with selected timing parameters of the CRT device;

[0060] Figure 3B shows a second schematic illustration of cardiac events sensed by an exemplary embodiment of a CRT device of the type of Figure 1 according to the present disclosure

[0061] 22.270P-WO / 02.03.2026and pacing pulses delivered by this CRT device together with selected timing parameters of the CRT device;

[0062] Figure 4A shows a third schematic illustration of the cardiac events sensed by a prior art CRT device and pacing pulses delivered by this CRT device together with selected timing parameters of the CRT device;

[0063] Figure 4B shows a fourth schematic illustration of cardiac events sensed by an exemplary embodiment of a CRT device of the type of Figure 2 according to the present disclosure and pacing pulses delivered by this CRT device together with selected timing parameters of the CRT device;

[0064] Figure 5A shows a fifth schematic illustration of the cardiac events sensed by a prior art CRT device and pacing pulses delivered by this CRT device together with selected timing parameters of the CRT device;

[0065] Figure 5B shows a sixth schematic illustration of cardiac events sensed by an exemplary embodiment of a CRT device of the type of Figure 2 according to the present disclosure and pacing pulses delivered by this CRT device together with selected timing parameters of the CRT device;

[0066] Figure 5C shows a seventh schematic illustration of cardiac events sensed by an exemplary embodiment of a CRT device of the type of Figure 2 according to the present disclosure and pacing pulses delivered by this CRT device together with selected timing parameters of the CRT device;

[0067] Figure 6A shows an eighth schematic illustration of the cardiac events sensed by a prior art CRT device and pacing pulses delivered by this CRT device together with selected timing parameters of the CRT device;

[0068] Figure 6B shows a nineth schematic illustration of cardiac events sensed by an exemplary embodiment of a CRT device of the type of Figure 2 according to the present disclosure and pacing pulses delivered by this CRT device together with selected timing parameters of the CRT device;

[0069] 22.270P-WO / 02.03.2026Figure 7A shows a tenth schematic illustration of the cardiac events sensed by a prior art CRT device and pacing pulses delivered by this CRT device together with selected timing parameters of the CRT device;

[0070] Figure 7B shows an eleventh schematic illustration of cardiac events sensed by an exemplary embodiment of a CRT device of the type of Figure 1 according to the present disclosure and pacing pulses delivered by this CRT device together with selected timing parameters of the CRT device;

[0071] Figure 8A shows a twelfth schematic illustration of the cardiac events sensed by a prior art CRT device and pacing pulses delivered by this CRT device together with selected timing parameters of the CRT device;

[0072] Figure 8B shows a thirteenth schematic illustration of cardiac events sensed by an exemplary embodiment of a CRT device of the type of Figure 1 according to the present disclosure and pacing pulses delivered by this CRT device together with selected timing parameters of the CRT device.

[0073] Figure 1A shows a system comprising a device for cardiac resynchronization therapy (CRT) 1 as example of an implantable medical device for stimulating the human or animal heart according to an embodiment of the present invention. The system further comprises a home monitoring system 2 serving as remote system. It is possible for the CRT device 1 to establish a wireless data communication with the home monitoring system 2.

[0074] The CRT 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 ventricle. Thus, the first electrode 5 is designed and arranged to sense right ventricular electric signals.

[0075] The CRT 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

[0076] 22.270P-WO / 02.03.2026defined 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 left ventricle. Thus, the second electrode 9 is designed and arranged to sense left ventricular electric signals.

[0077] Figure IB schematically illustrates individual components of the CRT device 1 of Figure 1A 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 electrode 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 home monitoring system 2 (confer Figure 1A).

[0078] Figures 2A and 2B show a system comprising a device for cardiac resynchronization therapy (CRT) 1 as example of an implantable medical device for stimulating the human or animal heart according to another embodiment of the present invention. The device 1 of Figures 2A and 2B comprises the same components as the device 1 of Figures 1A and IB. In addition, the device 1 comprises a third electrode 13 connected to the header 4. The third electrode 13 comprises a third tip electrode pole 14 and a third ring electrode pole 15 that is proximally arranged from the third tip electrode pole 14. A third sensing vector 16 is defined from the third ring electrode pole 15 to the third tip electrode pole 14. Electric cardiac signals sensed between the third tip electrode pole 14 and the third ring electrode pole 15, i.e., along the third sensing vector 16, are directly recorded within a heart chamber, typically the right atrium. Thus, the third electrode 14 is designed and arranged to sense right atrial electric signals. The third electrode 13 along with its third tip electrode 14 and third ring electrode 15 are operatively connected to or form part of the detection unit 31 and the stimulation unit 35.

[0079] Figure 3A shows a first schematic illustration of cardiac events sensed by a prior art CRT device and pacing pulses delivered by this CRT device together with selected timing parameters of the CRT

[0080] 22.270P-WO / 02.03.2026device. The CRT device is programmed to be operated as VVIR BiV-LV type device (i.e., a device with ventricular stimulation, ventricular sensing, inhibited operating mode, and a rate-adaptive frequency adaptation with biventricular stimulation, wherein the first paced ventricle is the left ventricle).

[0081] After a left ventricular pacing LVp has been delivered, a small interventricular interval, the so-called interventricular delay after pace VVp passes until a right ventricular pacing pulse RVp is applied by the CRT device. RVp

[0082] With the delivery of the initial left ventricular pacing pulse LVp, the left ventricular upper resynchronization interval LVURI (an embodiment of the presettable protective interval) is started. The left ventricular upper resynchronization interval LVURI has a twofold function. On the one hand, it defines the maximum left ventricular pacing rate in CRT devices employing biventricular cardiac re synchronization. Under this aspect, the left ventricular upper re synchronization interval LVURI is utilized to prevent sensible patients from experiencing palpitations at elevated resynchronization rates. On the other hand, the left ventricular upper re synchronization interval LVURI serves as protection against competitive left ventricular pacing after detected left ventricular senses.

[0083] The length of the left ventricular upper resynchronization interval LVURI is adjusted to the cardiac rate of the patient’s heart to be treated with the CRT device. Typically, the left ventricular upper resynchronization interval LVURI ends prior to the end of a pacing interval PL Thus, after another left ventricular pacing pulse LVp and another interventricular delay after pace VVp, a novel right ventricular pacing pulse RVp is delivered by the CRT device.

[0084] In case of a premature right ventricular depolarization RVs (either due to a right ventricular extrasystole or due to an increased cardiac rate), another small interventricular interval, a so-called interventricular interval after sense VVs which is ideally 0 ms, technically between 2 ms - 20 ms, ends within a persisting left ventricular upper resynchronization interval LVURI. During this left ventricular upper resynchronization interval LVURI, the delivery of a further left ventricular pacing pulse is inhibited. Consequently, only a logical event, namely a left ventricular phantom pacing pulse LVp(PH) is emitted. In addition, a left ventricular timing window T LVs is initiated that lasts until the detection of an intrinsic left ventricular depolarization LVs. The time between the right ventricular depolarization RVs and the left ventricular depolarization LVs is also referred to as interventricular sense delay IVSD.

[0085] 22.270P-WO / 02.03.2026Both the left ventricular phantom pacing pulse LVp(PH) and the sensed left ventricular depolarization LVs initiate further left ventricular upper re synchronization intervals LVURI. Consequently, different left ventricular upper re synchronization intervals LVURI overlap and inhibit the further delivery of a left ventricular pacing pulse LVp. A so-called LVURI lock-in situation has occurred that persistently prevents left ventricular pacing. It will not be possible for the CRT device to terminate the LVURI lock-in situation. Thus, the CRT device cannot perform its cardiac resynchronization functionality any longer.

[0086] Figure 3B shows a similar schematic illustration, however, not for a prior art device, but for an embodiment of an implantable medical device of the type of Figure 1A according to the present disclosure. This implantable medical device is a CRT device that is also programmed to be operated as VVIRBiV-LV type device (like the CRT device in Figure 3A). Here, a premature right ventricular depolarization RVs also initiates another left ventricular upper resynchronization interval LVURI at a time point at which the preceding left ventricular upper re synchronization interval LVURI has not yet terminated. Consequently, the delivery of a scheduled left ventricular pacing pulse LVp is inhibited. Instead, a left ventricular phantom pacing pulse LVp(PH) is emitted. Subsequently, an intrinsic left ventricular depolarization LVs can be detected which starts a novel left ventricular upper resynchronization interval LVURI. Thus, the situation is almost the same as in case of the prior art device.

[0087] However, upon detecting that a scheduled left ventricular pacing pulse LVp could not have been delivered due to an ongoing left ventricular upper re synchronization interval LVURI, the CRT device extends a subsequent pacing interval PI, as illustrated by the vertically hatched section of the third pacing interval. This extension or prolongation of the pacing interval PI results in a termination of this interval after expiration of the current left ventricular upper re synchronization interval LVURI. Consequently, the next scheduled left ventricular pacing pulse LVp can be delivered so that a resynchronization of the heart can take place. The delivered left ventricular pacing pulse LVp then starts a novel pacing interval PI that has the original length (i.e., it is shorter than the preceding, extended pacing interval PI). Afterwards, the heartbeat will take place in a regular and synchronized manner.

[0088] The extension of the pacing interval PI is performed in dependence on the actual cardiac rate of the patient’s heart. This ensures that the extended pacing interval PI is terminated only after a left ventricular upper resynchronization interval LVURI has expired.

[0089] 22.270P-WO / 02.03.2026Figure 4A shows another schematic illustration of the cardiac events sensed by a prior art CRT device and pacing pulses delivered by the CRT device together with selected timing parameters of the CRT device. In this comparative example, the CRT device is programmed as DDD BiV-LV type device (i.e., it employs a dual stimulation, a dual sensing, and a dual (inhibiting and triggered) operating mode; in addition, it performs a biventricular stimulation, wherein the left ventricle is the first paced ventricle).

[0090] In this example, an atrial pace Ap is delivered. After expiration of the atrioventricular interval AV (also referred to as atrioventricular conduction time), a left ventricular pacing pulse LVp is delivered. This initiates an interventricular delay after pace VVp, a left ventricular upper resynchronization interval LVURI and an upper rate interval UTI. Upon expiration of the interventricular delay after pace VVp, a right ventricular pacing pulse RVp is delivered to the right ventricle. After delivering another atrial pace Ap, the same sequence of events takes place. The interval between two atrial paces is indicated in Figures 4A and 4B by the letters “AA” It corresponds to the pacing interval PI.

[0091] Then, however, a left ventricular extrasystole LVES leads to a left ventricular depolarization LVs. Consequently, a novel left ventricular upper resynchronization interval LVURI is started, wherein the previous left ventricular upper resynchronization interval LVURI has not yet been terminated. The next scheduled left ventricular pacing pulse cannot be delivered since the previously started left ventricular upper resynchronization interval LVURI is still active. As a consequence, only a left ventricular phantom pacing pulse LVp(PH) is emitted. This leads to the start of a novel left ventricular upper re synchronization interval LVURI. Shortly afterwards, namely after elapsing of the interventricular delay after pace VVp, a right ventricular pacing pulse RVp is delivered. This right ventricular pacing pulse RVp results in a left ventricular depolarization LVs. This left ventricular depolarization LVs starts another left ventricular upper resynchronization interval LVURI. Consequently, three different left ventricular upper resynchronization intervals LVURI overlap. One of these left ventricular upper resynchronization intervals LVURI also persists at the time at which the next left ventricular pacing pulse LVp is scheduled so that once again only a left ventricular phantom pacing pulse LVp(PH) is emitted. Thus, the device has turned into an LVURI lock-in situation from which it cannot return by itself.

[0092] Figure 4B shows a similar situation like that of Figure 4A, however, using a CRT device being an embodiment of the type of Figure 2A of the present disclosure. This CRT device is also operated as DDD BiV-LV type device. The schematic illustration of Figure 4B starts in a cardiac cycle in which

[0093] 22.270P-WO / 02.03.2026an LVURI lock-in situation has already occurred due to an ongoing left ventricular upper resynchronization interval LVURI at the time at which a left ventricular pacing pulse LVp was scheduled. As a result, only a left ventricular phantom pacing pulse LVp(PH) is emitted that starts another left ventricular upper resynchronization interval LVURI. A subsequent left ventricular depolarization LVs starts another left ventricular upper resynchronization interval LVURI that persists at a time point at which the succeeding left ventricular pacing pulse was scheduled but is now inhibited. The emitted left ventricular phantom pacing pulse LVp(PH) starts a novel left ventricular upper re synchronization interval LVURI. Furthermore, the next intrinsic left ventricular depolarization LVs starts also a left ventricular upper re synchronization interval LVURI.

[0094] The CRT device has now detected that two left ventricular pacing pulses could not have been delivered as scheduled. Rather, two consecutive left ventricular phantom pacing pulses LVp(PH) have been emitted instead. This triggers an extension of the ongoing pacing interval AA. This is illustrated by the vertically hatched section of the second pacing interval AA. Due to the extension of this pacing interval AA, the latest left ventricular upper re synchronization interval LVURI is terminated before or upon the next left ventricular pacing pulse LVp is scheduled to be delivered. Consequently, this pacing pulse LVp can be delivered as scheduled (see arrow pointing to the right). This leads to a resynchronization of the right ventricular depolarization and the left ventricular depolarization, i.e., to a cardiac resynchronization. The left ventricular upper resynchronization interval LVURI that is initiated by the delivered left ventricular pacing pulse LVp regularly terminates prior to the next scheduled left ventricular pacing pulse so that the CRT device has left the LVURI lock-in situation and is able to provide the required cardiac resynchronization therapy, i.e., its normal functionality. Thus, a single extension of the pacing interval AA is sufficient to bring the CRT device out of the LVURI lock-in situation.

[0095] Figure 5 A shows another schematic illustration of the cardiac events sensed by a prior art CRT device and pacing pulses delivered by the CRT device together with selected timing parameters of the CRT device. Thereby, Figure 5 A illustrates a similar situation like that of Figure 4A. In this comparative example, the CRT device is again programmed as DDD BiV-LV type device.

[0096] In this example, an atrial depolarization is detected in form of an atrial sense As. After expiration of the atrioventricular interval AV (also referred to as atrioventricular conduction time), a left ventricular pacing pulse LVp is delivered. This initiates an interventricular delay after pace VVp, a left ventricular upper re synchronization interval LVURI and an upper rate interval UTI. Upon expiration of the interventricular delay after pace VVp, a right ventricular pacing pulse RVp is

[0097] 22.270P-WO / 02.03.2026delivered to the right ventricle. After detecting another atrial sense As, the same sequence of events takes place. The interval between two atrial senses is indicated in Figures 5A to 5C by the letters “PP”. Here, the intrinsic PP interval sets the pace for the ventricular pacing pulses and in that sense corresponds to the pacing interval PI of Figure 3B.

[0098] Then, however, a left ventricular extrasystole LVES leads to a left ventricular depolarization LVs. Consequently, a novel left ventricular upper resynchronization interval LVURI is started, wherein the previous left ventricular upper resynchronization interval LVURI has not yet been terminated. The next scheduled left ventricular pacing pulse cannot be delivered since the previously started left ventricular upper resynchronization interval LVURI is still active. As a consequence, only a left ventricular phantom pacing pulse LVp(PH) is emitted. This leads to the start of a novel left ventricular upper re synchronization interval LVURI. Shortly afterwards, namely after elapsing of the interventricular delay after pace VVp, a right ventricular pacing pulse RVp is delivered. This right ventricular pacing pulse RVp results in a left ventricular depolarization LVs. This left ventricular depolarization LVs starts another left ventricular upper resynchronization interval LVURI. Consequently, three different left ventricular upper resynchronization intervals LVURI overlap. One of these left ventricular upper resynchronization intervals LVURI also persists at the time at which the next left ventricular pacing pulse LVp is scheduled so that once again only a left ventricular phantom pacing pulse LVp(PH) is emitted. Thus, the device has turned into an LVURI lock-in situation from which it cannot return by itself.

[0099] Figure 5B shows a similar situation like that of Figure 5A, however, using a CRT device being an embodiment of the type of Figure 2A of the present disclosure. This CRT device is also operated as DDD BiV-LV type device. The schematic illustration of Figure 5B starts in a cardiac cycle in which an LVURI lock-in situation has already occurred due to an ongoing left ventricular upper resynchronization interval LVURI at the time at which a left ventricular pacing pulse LVp was scheduled. As a result, only a left ventricular phantom pacing pulse LVp(PH) is emitted that starts another left ventricular upper resynchronization interval LVURI. A subsequent left ventricular depolarization LVs starts another left ventricular upper resynchronization interval LVURI that persists at a time point at which the succeeding left ventricular pacing pulse was scheduled but is now inhibited. The instead emitted left ventricular phantom pacing pulse LVp(PH) starts a novel left ventricular upper re synchronization interval LVURI. Furthermore, the next intrinsic left ventricular depolarization LVs starts also a left ventricular upper re synchronization interval LVURI.

[0100] 22.270P-WO / 02.03.2026The CRT device has now detected that two left ventricular pacing pulses could not have been delivered as scheduled. Rather, two consecutive left ventricular phantom pacing pulses LVp(PH) have been emitted instead. This triggers an extension of the ongoing upper rate interval UTI. This is illustrated by the vertically hatched section of the upper rate interval UTI. Due to the extension of this upper rate interval UTI, the latest left ventricular upper resynchronization interval UVURI is terminated before or upon the next left ventricular pacing pulse UVp is scheduled to be delivered. Consequently, this pacing pulse UVp can be delivered as scheduled (see arrow pointing to the right). This leads to a resynchronization of the right ventricular depolarization and the left ventricular depolarization, i.e., to a cardiac resynchronization. The left ventricular upper resynchronization interval UVURI that is initiated by the delivered left ventricular pacing pulse UVp regularly terminates prior to the next scheduled left ventricular pacing pulse so that the CRT device has left the UVURI lock-in situation and is able to provide the required cardiac resynchronization therapy, i.e., its normal functionality. Thus, a single extension of the upper rate interval UTI is sufficient to bring the CRT device out of the UVURI lock-in situation.

[0101] Figure 5C shows a similar situation like that of Figure 4B, once again using a CRT device being an embodiment of the type of Figure 2A of the present disclosure. This CRT device is also operated as DDD BiV-UV type device. The schematic illustration of Figure 5C starts like the schematic illustration of Figure 5B in a cardiac cycle in which an UVURI lock-in situation has already occurred due to an ongoing left ventricular upper resynchronization interval UVURI at the time at which a left ventricular pacing pulse UVp was scheduled. Reference is made to the explanations given above with respect to Figure 5B.

[0102] The device, the functioning of which is illustrated in Figure 5C, combines an extension of the upper rate interval UTI (similarly like or in the same manner as the device, the function of which was illustrated in Figure 5B) with a reduction of the interventricular delay after pace VVp to 0 ms (i.e., it does not apply this interventricular delay after pace VVp in a single cardiac cycle at all). Due to the extension of the upper rate interval UTI, the latest left ventricular upper resynchronization interval UVURI is terminated before or upon the next left ventricular pacing pulse UVp is scheduled to be delivered. Consequently, this pacing pulse UVp can be delivered as scheduled (see arrow pointing to the right; the extension of the upper right interval UTI results in a later scheduling of the left ventricular pacing pulse UVp).

[0103] Since the interventricular delay after pace VVp has been set to 0 ms, a right ventricular pacing pulse RVp can be delivered at the same time as the left ventricular pacing pulse UVp. This leads to a totally

[0104] 22.270P-WO / 02.03.2026synchronized excitation of the left ventricle and the right ventricle in this cardiac cycle. Afterwards, all timing parameters are set to their previous values. The latest left ventricular upper rate interval LVURI terminates before the next left ventricular pacing pulse is scheduled. Consequently, this pacing pulse can be delivered as intended. Since the interventricular delay after pace VVp is applied with its previous value, the next right ventricular pacing pulse RVp is delivered only shortly after the left ventricular pacing pulse LVp (i.e., after expiration of the interventricular delay after pace VVp). Whether or not the interventricular delay after pace VVp is reduced (or even fully omitted by reducing it to 0 ms as in the example of Figure 5C) depends on the physiologic state of the heart to be treated. Different approaches can be applied to different time points if it turned out that the adjustment of a single timing parameter was not sufficient to resynchronize the heart again. Then, an adjustment of different timing parameters can have the desired effect.

[0105] Figure 6A shows another schematic illustration of the cardiac events sensed by a prior art CRT device and pacing pulses delivered by the CRT device together with selected timing parameters of the CRT device. Thereby, Figure 6A illustrates a similar situation like that of Figures 4A and 5A. In this comparative example, the CRT device is again programmed as DDD BiV-LV type device.

[0106] In this example, an atrial event Ax is detected that can be an atrial pace or an atrial sense. After expiration of the atrioventricular interval AV (also referred to as atrioventricular conduction time), a left ventricular pacing pulse LVp is delivered. This initiates an interventricular delay after pace VVp and a left ventricular upper re synchronization interval LVURI. Upon expiration of the interventricular delay after pace VVp, a right ventricular pacing pulse RVp is delivered to the right ventricle. The interval between two atrial events Ax is indicated in Figures 6A and 6B by the letters “PP”. Here, the PP interval (intrinsic or paced) sets the pace for the ventricular pacing pulses and in that sense corresponds to the pacing interval PL Then, however, a left ventricular extrasystole LVES leads to a left ventricular depolarization LVs. Consequently, a novel left ventricular upper resynchronization interval LVURI is started, wherein the previous left ventricular upper resynchronization interval LVURI has not yet been terminated. The next scheduled left ventricular pacing pulse cannot be delivered since the previously started left ventricular upper re synchronization interval LVURI is still active. As a consequence, only a left ventricular phantom pacing pulse LVp(PH) is emitted. This leads to the start of a novel left ventricular upper resynchronization interval LVURI. Shortly afterwards, namely after elapsing of the interventricular delay after pace VVp, a right ventricular pacing pulse RVp is delivered. This right ventricular pacing pulse RVp results in a left ventricular depolarization LVs. This left ventricular depolarization LVs starts another left ventricular upper re synchronization interval LVURI. Consequently, two different left ventricular

[0107] 22.270P-WO / 02.03.2026upper resynchronization intervals LVURI overlap. One of these left ventricular upper resynchronization intervals LVURI also persists at the time at which the next left ventricular pacing pulse LVp is scheduled so that once again only a left ventricular phantom pacing pulse LVp(PH) is emitted. Thus, the device has turned into an LVURI lock-in situation from which it cannot return by itself.

[0108] Figure 6A also illustrates the critical desynchronization interval CDI. This critical desynchronization interval CDI is calculated as CDI = T LVs + LVURI, i.e., as the sum of i) the measured time T LVs between the left ventricular phantom pacing pulse LVp(PH) and the next left ventricular depolarization LVs and ii) the left ventricular upper resynchronization interval LVURI. Since T LVs = VVp + IVSD (the sum of the interventricular delay after pace VVp and the interventricular sense delay IVSD), the critical desynchronization interval CDI can also be calculated as CDI = VVp + IVSD + LVURI. If the left ventricular interval is shorter than the critical desynchronization interval CDI, an LVURI lock-in situation can occur (e.g., by a premature event like a left ventricular extrasystole LVES, as illustrated in Figure 6A).

[0109] Figure 6B shows a similar situation like that of Figure 6A, however, using a CRT device being an embodiment of the type of Figure 2A of the present disclosure. This CRT device is also operated as DDD BiV-LV type device. The schematic illustration of Figure 6B starts in a cardiac cycle in which an LVURI lock-in situation is initiated due to a left ventricular extrasystole LVES, resulting in an ongoing left ventricular upper resynchronization interval LVURI at the time at which a left ventricular pacing pulse LVp was scheduled. As a result, only a left ventricular phantom pacing pulse LVp(PH) is emitted that starts another left ventricular upper re synchronization interval LVURI. A subsequent left ventricular depolarization LVs starts another left ventricular upper re synchronization interval LVURI that persists at a time point at which the succeeding left ventricular pacing pulse was scheduled but is now inhibited.

[0110] However, the interventricular delay after pace VVp is reduced to 0 ms in this embodiment (it could be generally less reduced so that an interventricular delay after pace VVp having a length of more than 0 ms would result). This reduction is illustrated by the vertically hatched section of the interventricular delay after pace VVp. Due to the reduction of the interventricular delay after pace VVp, the critical desynchronization interval CDI is shortened. Then, the current cardiac interval is longer than the critical desynchronization interval CDI so that the resynchronization becomes possible again. The reduction of the interventricular delay after pace VVp results in an earlier emission of the left ventricular phantom pacing pulse LVp(PH). Due to the ongoing left ventricular

[0111] 22.270P-WO / 02.03.2026upper re synchronization interval LVURI, a “real” left ventricular pacing pulse cannot yet be delivered. However, due to the reduction of the interventricular delay after pace VVp to 0 ms, a right ventricular pacing pulse RVp is delivered at the same time as the left ventricular phantom pacing pulse LVp(PH) (see arrow pointing to the left). This leads, on the one hand, to the start of a novel left ventricular upper resynchronization interval LVURI and, on the other hand, to an earlier occurrence of a left ventricular depolarization LVs and thus to an earlier start of the next left ventricular upper re synchronization interval LVURI. Consequently, this left ventricular upper resynchronization interval LVURI is terminated before the next regular left ventricular pacing pulse LVp is scheduled. Consequently, this left ventricular pacing pulse LVp can be delivered as intended so that the device has returned from the LVURI lock-in situation to its normal functionality by a onetime reduction of the interventricular delay after pace VVp. In the next cardiac cycle, the interventricular delay after pace VVp is restored to its previous value so that the subsequent pacing cycles can be performed as initially intended.

[0112] Figure 7A shows another schematic illustration of the cardiac events sensed by a prior art CRT device and pacing pulses delivered by the CRT device together with selected timing parameters of the CRT device. Thereby, Figure 7A illustrates a similar situation like that of Figure 3A. The CRT device is programmed to be operated as VVIR BiV-LV type device.

[0113] After a left ventricular pacing LVp has been delivered, the interventricular delay after pace VVp passes until a right ventricular pacing pulse RVp is applied by the CRT device.

[0114] With the delivery of the initial left ventricular pacing pulse, the left ventricular upper resynchronization interval LVURI is started. Due to a left ventricular extrasystole LVES, a left ventricular depolarization LVs is detected. This left ventricular depolarization LVs starts another left ventricular upper re synchronization interval LVURI. The subsequent interventricular delay after pace VVp ends within a persisting left ventricular upper resynchronization interval LVURI. During this left ventricular upper resynchronization interval LVURI, the delivery of a further left ventricular pacing pulse is inhibited. Consequently, only a left ventricular phantom pacing pulse LVp(PH) is emitted. In addition, a left ventricular timing window T LVs is initiated that lasts until the detection of an intrinsic left ventricular depolarization LVs.

[0115] Both the left ventricular phantom pacing pulse LVp(PH) and the sensed left ventricular depolarization LVs initiate further left ventricular upper re synchronization intervals LVURI. Consequently, different left ventricular upper re synchronization intervals LVURI overlap and inhibit

[0116] 22.270P-WO / 02.03.2026the further delivery of a left ventricular pacing pulse LVp. An LVURI lock-in situation has occurred that persistently prevents left ventricular pacing. It will not be possible for the CRT device to terminate the LVURI lock-in situation. Thus, the CRT device cannot perform its cardiac resynchronization functionality any longer.

[0117] Figure 7B shows a similar situation like that of Figure 7A, however, using a CRT device being an embodiment of the type of Figure 1A of the present disclosure. This CRT device is also operated as VVIR BiV-LV type device. The schematic illustration of Figure 7B starts in a cardiac cycle in which an LVURI lock-in situation is initiated due to a left ventricular extrasystole LVES, resulting in an ongoing left ventricular upper resynchronization interval LVURI at the time at which a left ventricular pacing pulse LVp was scheduled. As a result, only a left ventricular phantom pacing pulse LVp(PH) is emitted that starts another left ventricular upper re synchronization interval LVURI. A subsequent left ventricular depolarization LVs starts another left ventricular upper re synchronization interval LVURI that persists at a time point at which the succeeding left ventricular pacing pulse was scheduled but is now inhibited.

[0118] However, the interventricular delay after pace VVp is reduced to 0 ms in this embodiment (it could be generally less reduced so that a VVp having a length of more than 0 ms would result). This reduction is illustrated by the vertically hatched section of the interventricular delay after pace VVp. Due to the reduction of the interventricular delay after pace VVp, the critical desynchronization interval CDI is shortened. Then, the current cardiac interval is longer than the critical desynchronization interval CDI so that a re synchronization becomes possible again. The reduction of the interventricular delay after pace VVp results in an earlier emission of the left ventricular phantom pacing pulse LVp(PH). Due to the ongoing left ventricular upper resynchronization interval LVURI, a “real” left ventricular pacing pulse cannot yet be delivered. However, due to the reduction of the interventricular delay after pace VVp to 0 ms, a right ventricular pacing pulse RVp is delivered at the same time as the left ventricular phantom pacing pulse LVp(PH) (see arrow pointing to the left; same situation as in Figure 6B). This leads, on the one hand, to the start of a novel left ventricular upper re synchronization interval LVURI and, on the other hand, to an earlier occurrence of a left ventricular depolarization LVs and thus to an earlier start of the next left ventricular upper resynchronization interval LVURI. Consequently, this left ventricular upper resynchronization interval LVURI is terminated before the next regular left ventricular pacing pulse LVp is scheduled. Consequently, this left ventricular pacing pulse LVp can be delivered as intended so that the device has returned from the LVURI lock-in situation to its normal functionality by a one-time reduction of the interventricular delay after pace VVp. In the next cardiac cycle, the interventricular delay after

[0119] 22.270P-WO / 02.03.2026pace VVp is restored to its previous value so that the subsequent pacing cycles can be performed as initially intended.

[0120] Figure 8A shows another schematic illustration of the cardiac events sensed by a prior art CRT device and pacing pulses delivered by the CRT device together with selected timing parameters of the CRT device. Thereby, Figure 8A illustrates a similar situation like that of Figure 7A. However, the CRT device is programmed to be operated as VVIR BiV-RV type device (i.e., a device with ventricular stimulation, ventricular sensing, inhibited operating mode, and a rate-adaptive frequency adaptation with biventricular stimulation, wherein the first paced ventricle is the right ventricle).

[0121] After a right ventricular pacing RVp has been delivered, the interventricular delay after pace VVp passes until a left ventricular pacing pulse LVp is applied by the CRT device.

[0122] With the delivery of the initial left ventricular pacing pulse, the left ventricular upper resynchronization interval LVURI is started. Due to a left ventricular extrasystole LVES, a left ventricular depolarization LVs is detected. This left ventricular depolarization LVs starts another left ventricular upper re synchronization interval LVURI. The subsequent interventricular delay after pace VVp ends within a persisting left ventricular upper resynchronization interval LVURI. During this left ventricular upper resynchronization interval LVURI, the delivery of a further left ventricular pacing pulse is inhibited. Consequently, only a phantom pacing pulse LVp(PH) is emitted. In addition, a left ventricular timing window T LVs is initiated that lasts until the detection of an intrinsic left ventricular depolarization LVs.

[0123] Since in this embodiment T_LVs = IVSD - VVp (the difference between the interventricular sense delay IVSD and the interventricular delay after pace VVp), the critical desynchronization interval CDI can also be calculated as CDI = (IV SD - VVp + LVURI) . If the left ventricular interval is shorter than the critical desynchronization interval CDI, an LVURI lock-in situation can occur (e.g., by a premature event like a left ventricular extrasystole LVES, as illustrated in Figure 8A).

[0124] Both the left ventricular phantom pacing pulse LVp(PH) and the sensed left ventricular depolarization LVs initiate further left ventricular upper re synchronization intervals LVURI. Consequently, different left ventricular upper re synchronization intervals LVURI overlap and inhibit the further delivery of a left ventricular pacing pulse LVp. An LVURI lock-in situation has occurred that persistently prevents left ventricular pacing. It will not be possible for the CRT device to

[0125] 22.270P-WO / 02.03.2026terminate the LVURI lock-in situation. Thus, the CRT device cannot perform its cardiac resynchronization functionality any longer.

[0126] Figure 8B shows a similar situation like that of Figure 8A, however, using a CRT device being an embodiment of the type of Figure 1A of the present disclosure. This CRT device is also operated as VVIR BiV-RV type device. The schematic illustration of Figure 8B starts in a cardiac cycle in which an LVURI lock-in situation is initiated due to a left ventricular extrasystole LVES, resulting in an ongoing left ventricular upper resynchronization interval LVURI at the time at which a left ventricular pacing pulse LVp was scheduled. As a result, only a left ventricular phantom pacing pulse LVp(PH) is emitted that starts another left ventricular upper re synchronization interval LVURI. A previous right ventricular pacing pulse RVp initiates a left ventricular depolarization LVs that starts another left ventricular upper resynchronization interval LVURI.

[0127] In this embodiment, the interventricular delay after pace VVp is extended such that the next left ventricular pacing pulse LVp is only scheduled after termination of the ongoing left ventricular upper resynchronization interval LVURI. This extension is illustrated by the vertically hatched section of the interventricular delay after pace VVp. Due to the extension of the interventricular delay after pace VVp, the critical desynchronization interval CDI is shortened. Then, the current cardiac interval is longer than the critical desynchronization interval CDI so that a resynchronization becomes possible again. The extension of the interventricular delay after pace VVp results in later scheduling and emission of the left ventricular pacing pulse LVp (see arrow pointing to the right). Consequently, this left ventricular pacing pulse LVp can be delivered as intended so that the device has returned from the LVURI lock-in situation to its normal functionality by a one-time extension of the interventricular delay after pace VVp. In the next cardiac cycle, the interventricular delay after pace VVp is restored to its previous value so that the subsequent pacing cycles can be performed as initially intended.

[0128] As illustrated by the preceding examples, the presently claimed and described implantable medical device is able to automatically terminate an LVURI lock-in situation that occurred due to a temporarily reduced cardiac rate and thus to return to its normal functionality without external intervention.

[0129] 22.270P-WO / 02.03.2026

Claims

Claims1. Implantable medical device (1) for stimulating a human or animal heart, comprising a processor (32), a memory unit (33), a stimulation unit (35) configured to stimulate a human or animal heart, and a detection unit (31) configured to detect an electric signal of the same heart, wherein the detection unit (31) comprises a first electrode (5) for detecting right ventricular electric signals and a second electrode (9) for detecting left ventricular electric signals, 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 if a scheduled left ventricular pacing pulse (LVp) can be delivered with the second electrode (9), wherein a delivery of the left ventricular pacing pulse (LVp) is subject to an expiration of a presettable protective interval (LVURI) that is initiated by a preceding left ventricular pacing pulse (LVp) delivered with the second electrode (9), a preceding left ventricular depolarization (LVs) detected with the second electrode (9), or a preceding logic event (LVp(PH)) triggered instead of a preceding left ventricular pacing pulse (LVp) at the same time at which the preceding left ventricular pacing pulse (LVp) was scheduled to be delivered; andb) if the left ventricular pacing pulse (LVp) cannot be delivered since the presettable protective interval (LVURI) is not yet expired, adjusting at least one timing parameter of the implantable medical device (1) such that a following left ventricular pacing pulse (LVp) is scheduled to be delivered after expiration of a respective subsequent presettable protective interval (LVURI).

2. Implantable medical device according to claim 1, characterized in that the at least one timing parameter is chosen from the group consisting of a pacing interval (PI, AA), an upper rate interval (UTI), an atrioventricular interval (AV), and an interventricular delay after pace (Wp).

3. Implantable medical device according to claim 2, characterized in that adjusting the at least one timing parameter involves at least one of temporarily extending the pacing interval (PI, AA), temporarily extending the upper rate interval (UTI), temporarily extending the atrioventricular interval (AV), temporarily extending or reducing the interventricular delay after pace (Wp).22.270P-WO / 02.03.20264. Implantable medical device according to claim 2 or 3, characterized in that adjusting the at least one timing parameter involves temporarily extending the interventricular delay after pace (VVp) by an extension period lying in a range of from 5 ms to 100 ms, or temporarily reducing the interventricular delay after pace (VVp) to a final value lying in a range of from 0 ms to 50 ms.

5. Implantable medical device according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to keep the presettable protective interval (LVURI) constant.

6. Implantable medical device according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to adjust the at least one timing parameter only for a single cardiac cycle or for 2 to 10, in particular 3 consecutive cardiac cycles during a predeterminable time window.

7. Implantable medical device according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to determine if reestablishing of cardiac re synchronization has been successful and, if it has not been successful, to repeat steps a) and b) after a predeterminable first time period lying in a range of from 30s to 2 min or upon a reduction of the current heart rate.

8. Implantable medical device according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to perform step b) only 1 to 6 times per predeterminable time window, wherein the predeterminable time window in particular ranges from 5 minutes to 1 hour.

9. Implantable medical device according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to perform step b) only if at least 2 to 10, in particular 3 consecutive scheduled left ventricular pacing pulses (LVp) cannot be delivered since the presettable protective interval (LVURI) is not yet expired.

10. Implantable medical device according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to disable step b) for a predeterminable second time period if a cardiac re synchronization has not been successful during a third time period.22.270P-WO / 02.03.202611. Implantable medical device according to claim 10, characterized in that an unsuccessful cardiac resynchronization is assumed if N attempts for establishing cardiac re synchronization by adjusting at least one timing parameter during the third time period did not result in cardiac resynchronization, wherein N is a number lying in a range of from 20 to 1500.

12. Implantable medical device according to claim 10 or 11, characterized in that the third time period lies in a range of from 6 hours to 24 hours, and / or the second time period lies in a range of from 1 day to 7 days or extends to a scheduled follow-up examination.

13. Implantable medical device according to any of the preceding claims, characterized in that the computer-readable program causes the processor (32) to perform steps a) and b) for a maximum number of 2 to 6, in particular 3 cardiac cycles and disable step b) for 40 to 60, in particular 48 cardiac cycles upon reaching the maximum number and / or to perform steps a) to b) for 10 to 15 cardiac cycles, in particular 12 cardiac cycles within a total number of 40 to 60 cardiac cycles, in particular 48 cardiac cycles and disable step b) for 140 to 180 cardiac cycles, in particular for 160 cardiac cycles.

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, characterized by the following steps:a) determining if a scheduled left ventricular pacing pulse (LVp) can be delivered with a second electrode (9), wherein a delivery of the left ventricular pacing pulse (LVp) is subject to an expiration of a presettable protective interval (LVURI) that is initiated by a preceding left ventricular pacing pulse (LVp) delivered with the second electrode (9), a preceding left ventricular depolarization (LVs) detected with the second electrode (9), or a preceding logic event (LVp(PH)) triggered instead of a preceding left ventricular pacing pulse (LVp) at the same time at which the preceding left ventricular pacing pulse (LVp) was scheduled to be delivered; andb) if the left ventricular pacing pulse (LVp) cannot be delivered since the presettable protective interval (LVURI) is not yet expired, adjusting at least one timing parameter of the implantable medical device (1) such that a subsequent left ventricular pacing pulse (LVp) is scheduled to be delivered after expiration of a respective subsequent presettable protective interval (LVURI).22.270P-WO / 02.03.202615. Method for providing a cardiac resynchronization therapy to a patient in need thereof with 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 if a scheduled left ventricular pacing pulse (LVp) can be delivered with a second electrode (9), wherein a delivery of the left ventricular pacing pulse (LVp) is subject to an expiration of a presettable protective interval (LVURI) that is initiated by a preceding left ventricular pacing pulse (LVp) delivered with the second electrode (9), a preceding left ventricular depolarization (LVs) detected with the second electrode (9), or a preceding logic event (LVp(PH)) triggered instead of a preceding left ventricular pacing pulse (LVp) at the same time at which the preceding left ventricular pacing pulse (LVp) was scheduled to be delivered;b) if the left ventricular pacing pulse (LVp) cannot be delivered since the presettable protective interval (LVURI) is not yet expired, adjusting at least one timing parameter of the implantable medical device (1) such that a subsequent left ventricular pacing pulse (LVp) is scheduled to be delivered after expiration of a respective subsequent presettable protective interval (LVURI); andc) delivering the subsequent left ventricular pacing pulse (LVp) to the patient after expiration of the respective subsequent presettable protective interval (LVURI).22.270P-WO / 02.03.2026

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