EP-4736936-A1 - IMPLANTABLE MEDICAL SYSTEM AND METHOD FOR OPERATING

EP4736936A1EP 4736936 A1EP4736936 A1EP 4736936A1EP-4736936-A1

Abstract

The present invention relates to an implantable medical system for stimulating a patient's heart, comprising a memory unit (270), a processor (28), a stimulation unit (290) configured to stimulate the heart, and a detection unit (260) configured to detect a cardiac electric signal (250). The memory unit (270) stores a parameter allocation model which comprises a plurality of key sets (310, 420), each of which comprises a potential time of occurrence of at least one first event (110) in the cardiac electric signal (250) and each of which is mapped to at least one potential time of occurrence of a second event (130) in the cardiac electric signal (250) representing a repolarization of the myocardium. The memory unit (270) further stores a computer-readable read-out program that causes the processor (28) to perform the following steps when executed on the processor (28): - receiving a cardiac electric signal (250) comprising a plurality of events (110), - for at least one first event (110) in the received cardiac electric signal (250), determining an actual time of occurrence, - finding the key set in the list of key sets of the parameter allocation model that is closest to the actual time of occurrence, and - retrieving an estimation time from the parameter allocation model, which represents an estimation of the time of occurrence of the second event (130), based on the at least one potential time of occurrence of the at least one second event (130) to which the closest key set is mapped.

Inventors

WEISS, INGO
Ciesla, Catharina-Sophie

Assignees

BIOTRONIK SE & Co. KG

Dates

Publication Date: 20260506
Application Date: 20241105

Claims (15)

Implantable medical system for stimulating a patient's heart, comprising a memory unit (270), a processor (28), a stimulation unit (290) configured to stimulate the heart, and a detection unit (260) configured to detect a cardiac electric signal (250), characterized in that the memory unit (270) stores a parameter allocation model which comprises a plurality of key sets (310, 420), each of which comprises a potential time of occurrence of at least one first event (110) in the cardiac electric signal (250) and each of which is mapped to at least one potential time of occurrence of a second event (130) in the cardiac electric signal (250) representing a repolarization of the myocardium, wherein the memory unit (270) further stores a computer-readable read-out program that causes the processor (28) to perform the following steps when executed on the processor (28): - receiving a cardiac electric signal (250) comprising a plurality of events (110), - for at least one first event (110) in the received cardiac electric signal (250), determining an actual time of occurrence, - finding the key set in the list of key sets of the parameter allocation model that is closest to the actual time of occurrence, and - retrieving an estimation time from the parameter allocation model, which represents an estimation of the time of occurrence of the second event (130), based on the at least one potential time of occurrence of the at least one second event (130) to which the closest key set is mapped.
Implantable medical system according to claim 1, characterized in that the at least one first event (110) represents a repolarization of the myocardium or a depolarization of the myocardium.
Implantable medical system according to one of claims 1 or 2, characterized in that the key set comprises a potential time of occurrence of a plurality of first events (110) wherein the potential time of occurrence of the plurality of first events (110) is mapped to the potential time of occurrence of the at least one second event (130).
Implantable medical system according to one of claims 1 to 3, characterized in that the parameter allocation model has the form of a look-up table (300).
Implantable medical system according to one of the preceding claims, characterized in that retrieval of the estimation time based on the potential time of occurrence of the second event (130) to which the closest key set is mapped comprises interpolating the estimation time from the potential times of occurrence of the second event (130) to which the closest and second closest key sets are mapped or extrapolating the estimation time from the potential time of occurrence of the at least one second event (130).
Implantable medical system according to one of the preceding claims, characterized in that potential times of occurrence of the at least one first event (110) in the cardiac electric signal (250) are formed by time intervals defining a rasterization into look-up classes (400).
Implantable medical system according to claim 6, characterized in that look-up classes (400) are distinguished by width in time so that the rasterization is not equidistant.
Implantable medical system according to one of claims 6 or 7, characterized in that the look-up classes (400) are anchored at an anchor point in time and extend 2 % to 20 % from the anchor point in both directions in time.
Implantable medical system according to one of the preceding claims, characterized in that retrieving the estimation time comprises retrieving a representative value of several potential times of occurrence of the at least one second event (130) to which the closest key set is mapped.
Implantable medical system according to one of the preceding claims, characterized in that the computer-readable read-out code causes the processor (28) to generate at least one stimulation pulse emitted by the stimulation unit (290) during or outside the estimation time.
Implantable medical system according to one of the preceding claims, characterized in that the computer-readable read-out code causes the processor (28) to emit at least one electric pulse by the stimulation unit (290) or a communication unit of the implantable medical system outside the estimation time.
Implantable medical system for stimulating a patient's heart, comprising a memory unit (270), a processor (28), a stimulation unit (290) configured to stimulate the heart, and a detection unit (260) configured to detect a cardiac electric signal (250), characterized in that the memory unit (270) stores a computer-readable record program that causes the processor (28) to perform the following steps when executed on the processor (28): - receiving a cardiac electric signal (250) comprising a plurality of events, - for at least one first event (110) and at least one second event (130) in the received cardiac electric signal (250), determining an actual time of occurrence, - storing the actual time of occurrence of the at least one second event (130) allocated to a key set corresponding to the actual time of occurrence of the at least one first event (110), so that the key set is mapped to the actual time of occurrence of the second event (130).
Implantable medical system according to claim 12, characterized in that the memory unit (270) comprises a ring buffer storage for each key set in which the actual time of occurrence of the at least one second event (130) is stored.
Implantable medical system according to claim 12, characterized in that the memory unit (270) is configured to store a representative value of several actual times of occurrence of at least one second event (130) under one key set which representative value is updated when storing the actual time of occurrence of the at least one second event (130).
Method for operating an implantable medical system, in particular according to any of the preceding claims, characterized by receiving a cardiac electric signal (250) comprising a plurality of events, and one or both of the following sets of steps: a) for at least one first event (110) and at least one second event (130) in the received cardiac electric signal (250), determining an actual time of occurrence and b) storing the actual time of occurrence of the at least one second event (130) allocated to a key set corresponding to the actual time of occurrence of the at least one first event (110), so that the key set is mapped to the actual time of occurrence of the second event (130); or a) for at least one first event (110) in the received cardiac electric signal (250), determining an actual time of occurrence, b) finding a key set in a list of key sets of a parameter allocation model that is closest to the actual time of occurrence, and c) retrieving an estimation time from the parameter allocation model, which represents an estimation of a time of occurrence of a second event (130), based on an at least one potential time of occurrence of the at least one second event (130) to which the closest key set is mapped.

Description

The present invention relates to an implantable medical system according to the preamble of claims 1 and 12 and to a method of operating an implantable medical system according to the preamble of claim 15. The implantable medical system may comprise a non-transvenous implantable cardioverter-defibrillator device generally designed for implantation external to a patient's heart. A non-transvenous implantable cardioverter-defibrillator device, in short non-transvenous ICD, comprises a stimulation unit and a processor, and at least one lead comprising a shock electrode for emitting an electrical shock pulse externally to a patient's heart. The lead is connected to the stimulation unit. The stimulation unit forms part of a generator device that may, for example, be implanted subcutaneously in a patient. The lead, in a connected state, extends from the generator device, the lead being implanted such that it fully rests outside of the patient's heart. The lead may for example extend from the generator device towards a location in the region of the patient's sternum, the shock electrode hence being placed outside of the patient's heart for emitting an electrical shock pulse at a location external to the patient's heart. The term "non-transvenous" in this respect, in particular, shall express that the lead of the non-transvenous implantable cardioverter-defibrillator device does not extend transvenously into the heart, but fully rests outside of the patient's heart. The implantable medical system comprising the non-transvenous implantable cardioverter-defibrillator device, in particular, is designed for emitting electrical shocks in case life-threatening arrhythmias of a patient's heart are detected. By means of an electrical shock, a defibrillation shall be achieved in order to reset the cardiac rhythm back to a normal state. In some instances, T wave shocks are applied with a fixed, manually predetermined delay of the shock with respect to the previous QRS complex in the electrocardiogram (Barold, H. S., & Wharton, J. M. (1997)). Ventricular fibrillation resulting from synchronized internal atrial defibrillation in a patient with ventricular preexcitation. Journal of Cardiovascular Electrophysiology, 8(4), 436-440). However, this approach does not consider possible variations in the cardiac rhythm of the patient. When operating the implantable medical system, it is helpful to estimate a time of occurrence of the next T wave of the cardiac rhythm of the patient. Typically, shock pulses for achieving a cardioversion are applied outside the T wave. If the cardioversion would be performed during the T wave, there is a high risk of inducing ventricular fibrillation by the cardioversion shock pulses. In some instances, such ventricular fibrillation of the patient's heart is desired. For this purpose, sequences of pulse bursts are emitted by the shock electrode. As such pulse bursts may be emitted over a duration of several seconds and may be delivered with substantial energy, such pulse bursts may cause a significant stress on a patient and its muscular system, causing potentially postoperative pain to a patient. R-wave synchronized inducing of ventricular fibrillation has been described by Wylie Jr. et al. (Wylie Jr, J. V., Essebag, V., Reynolds, M. R., & Josephson, M. E. (2009). Inducibility of Atrial Fibrillation with a Synchronized External Low Energy Shock Post-Pulmonary Vein Isolation Predicts Recurrent Atrial Fibrillation. Journal of Cardiovascular Electrophysiology, 20(1), 29-36). However, an exact knowledge on the time of occurrence of the T wave increases the efficacy of such pulse bursts. In some instances, an electric (or galvanically coupled) communication between different implantable or implanted medical devices is desired. The risk of ventricular fibrillation is significantly reduced if any electric communication pulses are emitted by such devices only outside the T waves of the patient's cardiac rhythm. Thus, there is a general need of an estimation of the time of occurrence of the T wave in the patient's cardiac rhythm for these different applications of emitting electric pulses during or outside the T wave. It is an object of the present invention to provide an implantable medical system for stimulating a patient's heart, comprising a memory unit, a processor, a stimulation unit configured to stimulate the heart, and a detection unit configured to detect a cardiac electric signal and a method for operating such system, which allow for a more exact estimation of the occurrence of the T wave in a patient's cardiac rhythm. According to a first aspect of the invention, this object is achieved with an implantable medical system wherein the memory unit stores a parameter allocation model which comprises a plurality of key sets, each of which comprises a potential time of occurrence of at least one first event in the cardiac electric signal and each of which is mapped to at least one potential time of occur