Patent Application
20230233866
The present invention relates to an implantable medical device for stimulating a human or animal heart according to the preamble of claim 1, to a method for determining a dislocation of the stimulation electrode of such an implantable medical device according to the preamble of claim 13, and to a computer program product according to the preamble of claim 14.
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.
For properly carrying out all functions of such an implantable medical device, it is mandatory that its stimulation electrode is correctly positioned. However, electrode dislocation often occurs during the lifetime of such an implantable medical device.
U.S. Pat. No. 5,713,932 discloses a method and an apparatus for determining atrial lead dislocation. For this purpose, a test pace pulse is applied to the atrial pace/sense electrode. Afterwards, the immediately following ventricular depolarization is detected by a ventricular sense electrode. The interval between the delivered atrial pace pulse and the detected ventricular depolarization is compared with a threshold interval value. If the measured interval is longer than the threshold interval, it is assumed that the atrial pace/sense electrode is in contact with the right atrium and thus correctly positioned.
International Publication No. WO 00/66219 A1 discloses a method and an apparatus for determining the occurrence of a dislocation of an atrial electrode in a cardiac stimulation device. The apparatus comprises control means for employing an atrial pulse generator to provide atrial pacing pulses to the atrial electrode at a first energy level and subsequently employing the atrial pulse generator to provide higher energy atrial pacing pulses to the atrial electrode at a second, greater energy level. Once again, the intervals between pacing pulse and a response pulse are determined. Their duration is used for determining whether the atrial electrode is properly located.
Thus, the known methods for identifying a dislocation of an electrode rely on an evaluation of a time duration between a pacing pulse and the respective ventricular response signal. However, relying only on a time information can lead to a false positive identification of ventricular signals since noise and irregular cardiac signals might also be identified as regular and proper ventricular response to an atrial stimulation. This, in turn, might lead to the incorrect identification of an atrial electrode as being properly located, wherein the electrode is in fact dislocated.
The present disclosure is directed toward overcoming one or more of the above-mentioned problems, though not necessarily limited to embodiments that do.
It is an object of the present invention to provide an implantable medical device for stimulating a human or animal heart and a corresponding method by which an electrode dislocation can be more accurately determined than according to devices and methods known from prior art.
At least this object is achieved with an implantable medical device for stimulating a human or animal heart having the features of claim 1. Such a device comprises a processor, a memory unit, a stimulation unit, and a detection unit. The stimulation unit comprises a stimulation electrode and is configured to stimulate a first cardiac region of a human or animal heart. The detection unit is configured to detect an intracardiac electrogram (IEGM) at a second cardiac region. The second cardiac region is distinct from the first cardiac region. To be more precise, the second cardiac region is a ventricle of the human or animal heart that is to be stimulated.
According to the present invention, the memory unit comprises a computer-readable program that causes the processor to perform the steps explained in the following when executed on the processor.
First, a stimulation pulse (pacing pulse) is delivered to a human or animal heart by the stimulation unit. If the stimulation electrode of the stimulation unit is correctly positioned, the stimulation pulse is delivered to the first cardiac region. If the stimulation electrode is improperly located (dislocated), the stimulation pulse might be delivered to another cardiac region, such as the second cardiac region.
Afterwards, a time and at least one morphologic parameter of the signal of an intracardiac electrogram is evaluated. This intracardiac electrogram is detected by the detection unit, i.e., it represents a ventricular activity of the stimulated heart. The signal has been generated in response to the stimulation pulse, i.e., the signal is in particular due to a ventricular depolarization immediately following the stimulation pulse. The at least one morphologic parameter is chosen from the group comprising of:
To give an example, if the signal has an amplitude of -3 mV, the absolute value of the amplitude is 3 mV. Likewise, if the signal has an amplitude of +2.5 mV, the absolute value of the amplitude is 2.5 mV.
Finally, a dislocation of the stimulation electrode is identified if two conditions are met at the same time. According to the first condition, the time of the signal needs to be below a first threshold value. In this context, the term “time of the signal” means “time of the signal after delivery of the stimulation pulse”. According to the second condition, the morphologic parameter needs to exceed at least one further threshold value. In this context, different threshold values are typically chosen for different morphologic parameters.
Expressed in other words, the presently claimed invention does not rely only on a time information of a ventricular signal detected in response to a stimulation pulse, but also considers at least one morphologic criterion of the detected signal in order to determine whether or not a dislocation of the stimulation electrode has been taken place. By also considering such a morphologic criterion (morphologic parameter), ventricular signals that can be attributed to noise or irregular cardiac signals can be safely separated from real ventricular signals so that a higher reliability of the dislocation identification as possible.
In an embodiment, the implantable medical device is a pacemaker such as an implantable pulse generator (IPG). In an embodiment, the implantable medical device is an implantable cardioverter/defibrillator (ICD). In an embodiment, the implantable medical device is specifically adapted to deliver an atrial antitachycardial therapy to the heart to be stimulated.
In an embodiment, a dislocation of the stimulation electrode is identified not only on the basis of a single evaluated signal, but rather on the basis of a plurality of ventricular signals caused by a previous stimulation pulse delivered by the stimulation unit. To give an example, 2, 3, 4, 5, 6, 7, 8, 9 or 10 ventricular signals can be evaluated as described above in order to identify a dislocation of the stimulation electrode. In an embodiment, 2 to 10, in particular 3 to 9, in particular 4 to 8, in particular 5 to 7 ventricular signals are evaluated is in order to identify a dislocation of the stimulation electrode.
In an embodiment, the stimulation electrode is considered to be dislocated if n-m evaluated ventricular signals fulfil the two criteria explained above. In this context, n is a number between 1 and 10, in particular between 2 and 9, in particular between 3 and 8, in particular between 4 and 7, in particular 5 or 6. Furthermore, m is a number between 0 and 9, in particular between 1 and 8, in particular between 2 and 7, in particular between 3 and 6, in particular 4 or 5. Furthermore, m is always smaller than n. To give an example, if 3 ventricular signals are evaluated (n = 3) and 2 of these signals (m = 1) fulfil the two conditions explained above, the stimulation electrode is considered to be dislocated.
In an embodiment, the computer-readable program causes the processor to evaluate two morphologic parameters of the ventricular signal, namely both the amplitude of the signal and the width of the signal. In doing so, the reliability of a correct identification of a ventricular signal can be increased.
In an embodiment, the computer-readable program causes the processor to identify dislocation of the stimulation electrode if the following two conditions are met. According to the first condition, the time of the signal is below a first threshold value (as already explained above). According to the second condition, the absolute value of the amplitude of the signal needs to traverse the further threshold value for the amplitude in two instances within a time exceeding the further threshold value for the width of the signal. The following example might be helpful in illustrating this embodiment: assuming a ventricular signal having a maximum amplitude of 4 mV is evaluated. Further assuming that the further threshold value for the amplitude is 2 mV, the absolute value of the amplitude of the signal traverses the maximum threshold once when the signal increases towards its maximum amplitude and once when the signal decreases again. Thus, it traverses the further threshold value for the amplitude in two instances. If the time distance between the two traversing events is longer than the further threshold value for the signal width, the two conditions are met. In such a case, the morphologic evaluation of the signal strongly indicates that the signal is a real signal and not caused by artefacts or noise. Rather, in case of noise or artefacts, the time distance between two instances of traversing the further threshold value for the amplitude would rather be significantly shorter than the further threshold value for the signal with. Thus, by combining a time information and morphologic criteria, a very accurate evaluation of the ventricular signal is possible.
In an embodiment, the first threshold value is at least 80 ms. In an embodiment, the first threshold value lies in a range between 80 ms and 200 ms, in particular between 50 ms and 90 ms, in particular between 120 ms and 160 ms. If the ventricular response signal is detected more closely to the stimulation pulse than after an expiration of the first threshold value, it is very likely that the stimulation pulse has not stimulated an atrial region of the heart, but rather directly a ventricular region (leading to a very quick ventricular response). Then, the stimulation electrode is considered to be dislocated since it directly stimulated a ventricular region of the heart (i.e., the second cardiac region), not a region distinct from the second cardiac region.
In an embodiment, the further threshold value for the amplitude is at least 2 mV. In an embodiment, the further threshold value for the amplitude lies in a range between 2 mV and 10 mV, in particular between 3 mV and 9 mV, in particular between 4 mV and 8 mV, in particular between 5 mV and 7 mV.
In an embodiment, the further threshold value for the width is at least 4 ms measured at an absolute value of the amplitude corresponding to the further threshold for the amplitude. In an embodiment, the further threshold for the width lies in a range between 4 ms and 40 ms, in particular between 6 ms and 18 ms, in particular between 8 ms and 16 ms, in particular between 10 ms and 14 ms, in particular between 10 ms and 35 ms, in particular between 15 ms and 30 ms.
In an embodiment, the at least one further threshold value is a relative value being determined in relation to a signal amplitude of the R wave of at least one cardiac cycle directly (immediately) or indirectly preceding the evaluated signal. Thus, the specific behavior of the heart to be stimulated can be taken into account in this embodiment in order to determine the at least one further threshold value for the morphologic parameter of the ventricular signal to be evaluated.
In an embodiment, the first cardiac region is an atrium or a His bundle of a human or animal heart. Thus, the stimulation electrode is, in this embodiment, configured and designed to either stimulate an atrium (in particular the right atrium) of the heart or the His bundle of the heart. By such stimulation, a ventricular response signal is to be expected if the atrioventricular stimulation pathway is still intact. If, however, a ventricular response signal can be detected much earlier than expected, this indicates that the stimulation electrode is no longer located within the atrium or at the His bundle, but rather has been dislocated into the ventricle of the heart that is to be stimulated. Then, this electrode can no longer be used for delivering stimulation pulses in the course of an atrial antitachycardial stimulation or in the course of other atrial stimulations or His bundle stimulations.
In an embodiment, the stimulation unit is configured and designed to apply an atrial antitachycardial stimulation to an atrium of a human or animal heart. Such an atrial antitachycardial stimulation can also be denoted as atrial antitachycardial pacing (atrial ATP). It is mandatory for such a stimulation that the stimulation electrode used is properly located within the atrium of the heart to be stimulated.
In an embodiment, the identification of the dislocation of the stimulation electrode can be carried out prior to, during, or after the delivery of a stimulation pulse or a stimulation therapy. An application prior to or during the (intended) delivery of stimulation pulses or a stimulation therapy is particularly effective against undesired side effects of the stimulation pulses or the stimulation therapy.
In an embodiment, the computer-readable program causes the processor to prevent delivery of the stimulation pulses by the stimulation unit if a dislocation of the stimulation electrode has been identified. This safety procedure prevents delivery of stimulation pulses in case of an undesired dislocation of the stimulation electrode. In an embodiment, such interruption or blockage of a stimulation therapy can be communicated to a remote monitoring system so as to inform medical staff about the identified electrode dislocation. In such a case, it is possible to request the patient to visit a medical doctor in order to further examine and/or to correct the detected electrode dislocation.
In an embodiment, the computer-readable program causes the processor to perform the steps of delivering a stimulation pulse, of evaluating a time and at least one morphologic parameter of the signal of an intracardiac electrogram and of identifying a dislocation of the stimulation electrode in a time window of 5 seconds to 30 seconds, in particular of 10 seconds to 25 seconds, in particular of 15 seconds to 20 seconds prior to an intended stimulation of the first cardiac region. Thus, the test whether or not the stimulation electrode is dislocated is, in this embodiment, carried out immediately prior to the therapeutic stimulation of the heart. Then, a delivery of stimulation pulses can be prevented in case of a dislocation of the electrode. This might be helpful and medically required since a stimulation by a dislocated stimulation electrode can have severe negative effects outbalancing any positive effects achieved by such stimulation.
In an embodiment, the computer-readable program causes the processor to perform the step of delivering a stimulation pulse at the beginning of a time window in which no intrinsic ventricular signal is expected to occur. Then, any interferences with intrinsic ventricular signals are avoided. Such time window can be a time window lying in a range of 50 ms to 1 second, in particular of 60 ms to 900 ms, in particular of 70 ms to 800 ms, in particular of 80 ms to 700 ms, in particular of 90 ms to 600 ms, in particular of 100 ms to 500 ms, in particular of 150 ms to 400 ms, in particular of 200 ms to 350 ms, in particular of 250 ms to 300 ms.
In an aspect, the present invention relates to a method for determining a dislocation of a stimulation electrode of the stimulation unit. The stimulation unit forms part of an implantable medical device for stimulating a human or animal heart, in particular an implantable medical device according to the preceding explanations. Furthermore, the stimulation unit is configured to stimulate a first cardiac region of a human or animal heart. The method comprises the steps explained in the following.
First, a stimulation pulse is delivered to a human or animal heart by the stimulation unit. If the stimulation electrode of the stimulation unit is correctly positioned, the stimulation pulse is delivered to the first cardiac region. If the stimulation electrode is improperly located (dislocated), the stimulation pulse might be delivered to another cardiac region, such as the second cardiac region.
Afterwards, a time and at least one morphologic parameter of the signal of an intracardiac electrogram is evaluated. This intracardiac electrogram is detected by the detection unit, i.e., it represents a ventricular activity of the stimulated heart. The signal has been generated in response to the stimulation pulse, i.e., the signal is in particular due to a ventricular depolarization immediately following the stimulation pulse. The at least one morphologic parameter is chosen from the group comprising of:
Finally, a dislocation of the stimulation electrode is identified if two conditions are met at the same time. According to the first condition, the time of the signal needs to be below a first threshold value. According to the second condition, the morphologic parameter needs to exceed at least one further threshold value. In this context, different threshold values are typically chosen for different morphologic parameters.
In an aspect, the present invention relates to computer program product (in particular to a non-transitory computer program product) comprising computer-readable code that causes the processor to perform the steps explained in the following when executed on the processor.
First, a stimulation pulse is delivered to a human or animal heart by a stimulation unit comprising a stimulation electrode. If the stimulation electrode is correctly positioned, the stimulation pulse is delivered to the first cardiac region. If the stimulation electrode is improperly located (dislocated), the stimulation pulse might be delivered to another cardiac region, such as the second cardiac region.
Afterwards, a time and at least one morphologic parameter of the signal of an intracardiac electrogram is evaluated. This intracardiac electrogram is detected by the detection unit, i.e., it represents a ventricular activity of the stimulated heart. The signal has been generated in response to the stimulation pulse, i.e., the signal is in particular due to a ventricular depolarization immediately following the stimulation pulse. The at least one morphologic parameter is chosen from the group comprising of:
Finally, a dislocation of the stimulation electrode is identified if two conditions are met at the same time. According to the first condition, the time of the signal needs to be below a first threshold value. According to the second condition, the morphologic parameter needs to exceed at least one further threshold value. In this context, different threshold values are typically chosen for different morphologic parameters.
In a further aspect, the present invention relates to a method of treatment of a human or animal patient in need of such treatment by means of 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 implantable medical device comprises a processor, a memory unit, a stimulation unit and a detection unit. The stimulation unit comprises a stimulation electrode and is configured to stimulate a first cardiac region of a human or animal heart. The detection unit is configured to detect an intracardiac electrogram (IEGM) at a second cardiac region. The second cardiac region is distinct from the first cardiac region. To be more precise, the second cardiac region is a ventricle of the human or animal heart that is to be stimulated.
First, a stimulation pulse is delivered to a human or animal heart by the stimulation unit. If the stimulation electrode of the stimulation unit is correctly positioned, the stimulation pulse is delivered to the first cardiac region. If the stimulation electrode is improperly located (dislocated), the stimulation pulse might be delivered to another cardiac region, such as the second cardiac region.
Afterwards, a time and at least one morphologic parameter of the signal of an intracardiac electrogram is evaluated. This intracardiac electrogram is detected by the detection unit, i.e., it represents a ventricular activity of the stimulated heart. The signal has been generated in response to the stimulation pulse, i.e., the signal is in particular due to a ventricular depolarization immediately following the stimulation pulse. The at least one morphologic parameter is chosen from the group comprising of:
Then, a dislocation of the stimulation electrode is identified if two conditions are met at the same time. According to the first condition, the time of the signal needs to be below a first threshold value. According to the second condition, the morphologic parameter needs to exceed at least one further threshold value. In this context, different threshold values are typically chosen for different morphologic parameters.
Finally, stimulation pulses are delivered to the human or animal heart by the stimulation unit if no dislocation of the stimulation electrode was identified in the preceding identifying step. In this context, the stimulation pulses serve for an atrial antitachycardial stimulation. If, on the other hand, a dislocation of the stimulation electrode has been identified in the preceding identifying step, delivering of stimulation pulses for atrial antitachycardial stimulation to the human or animal heart is prevented. Thus, a correct (proper) location of the stimulation electrode decides whether or not an atrial antitachycardial stimulation is carried out.
Expressed in other words, the determination of the correct positioning of the stimulation electrode is a mandatory prerequisite to be fulfilled in order to perform the intended atrial antitachycardial stimulation. Thus, the determination whether or not the stimulation electrode is properly located serves here as safety step in this medical method.
All embodiments of the implantable medical device can be combined in any desired way and can be transferred either individually or in any arbitrary combination to the described methods and the described computer program product. Likewise, all embodiments of the described methods can be combined in any desired way and can be transferred either individually or in any arbitrary combination to the respective other method, to the implantable medical device and to the computer program product. Finally, all embodiments described with respect to the computer program product can be combined in any desired way and can be transferred either individually or in any arbitrary combination to the described implantable medical device or to the described methods.
Additional features, aspects, objects, advantages, and possible applications of the present disclosure will become apparent from a study of the exemplary embodiments and examples described below, in combination with the Figures and the appended claims.
Further details of aspects of the present invention will be described in the following making reference to exemplary embodiments and accompanying Figures. In the Figures:
The sensing electrode 3 serves for detecting an intracardiac electrogram 7 comprising ventricular signals such as ventricular depolarizations.
If a stimulation pulse 8 is delivered to the atrium 4 by the stimulation electrode 2, no significant ventricular signals can be observed in the intracardiac electrogram 7 within the depicted time interval. This is due to the fact that a ventricular depolarization responsive to the atrial stimulation pulse 8 only takes place after the atrioventricular response time (atrioventricular interval) has been passed. However, the intracardiac electrogram 7 only shows a time period shorter than the atrioventricular interval.
If now a stimulation pulse 8 is delivered by the stimulation electrode 2, an immediate ventricular response 9 can be observed in the intracardiac electrogram. This is due to the fact that the ventricular stimulation results in a very quick ventricular depolarization (much quicker than in case of atrioventricular stimulus conduction). The ventricular signal 9 occurs at a time 10 being lower than a threshold time 11 (serving as first threshold value). Although the voltage of the ventricular signal 9 is negative, its absolute value exceeds a set voltage threshold 12 (serving as further threshold value). Since the ventricular signal 9 occurs at a time point 10 being shorter than the set threshold 11 and has an amplitude, the absolute value of which exceeds the set amplitude threshold 12, the ventricular signal 9 is considered as real ventricular signal indicative for a dislocation of the stimulation electrode 2.
A similar situation is depicted in
Summarizing, ventricular signal responses to an atrial stimulation as shown in
It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teachings of the disclosure. The disclosed examples and embodiments are presented for purposes of illustration only. Other alternate embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention, which is to be given the full breadth thereof. Additionally, the disclosure of a range of values is a disclosure of every numerical value within that range, including the end points.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20181572.7 | Jun 2020 | EP | regional |
This application is the United States National Phase under 35 U.S.C. § 371 of PCT International Patent Application No. PCT/EP2021/064639, filed on Jun. 01, 2021, which claims the benefit of European Patent Application No. 20181572.7, filed on Jun. 23, 2020, the disclosures of which are hereby incorporated by reference herein in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/064639 | 6/1/2021 | WO |
