IMPLANTABLE MEDICAL DEVICE WITH ELECTRODE DISLOCATION RECOGNITION

Abstract

An implantable medical device for stimulating a heart, includes a stimulation electrode configured to stimulate a first cardiac region of the heart, and a detection unit configured to detect an intracardiac electrogram at a second cardiac region (ventricle) of the heart. In operation, the device: delivers a stimulation pulse to the heart; evaluates a time and at least one morphologic parameter of a responsive signal of an intracardiac electrogram, wherein the at least one morphologic parameter is chosen from: an absolute value of the signal amplitude, a width of the signal, a positive, negative and/or total area under at least a part of the signal, and a number of occurrences and/or time of occurrence of zero crossings of the signal; and identifies a dislocation of the stimulation electrode if the time of the signal is below a first threshold value and the morphologic parameter exceeds a further threshold value.

Claims

1. Implantable medical device for stimulating a human or animal heart, comprising a processor, a memory unit, a stimulation unit comprising a stimulation electrode configured to stimulate a first cardiac region of a human or animal heart, and a detection unit configured to detect an intracardiac electrogram at a second cardiac region of the same heart, the second cardiac region being a ventricle, wherein the memory unit comprises a computer-readable program that causes the processor to perform the following steps when executed on the processor: delivering a stimulation pulse to a human or animal heart by the stimulation unit; evaluating a time and at least one morphologic parameter of a signal of an intracardiac electrogram detected by the detection unit, the signal having been caused in response to the stimulation pulse, wherein the at least one morphologic parameter is chosen from the group comprising of: an absolute value of an amplitude of the signal, a width of the signal, a positive and/or a negative and/or a total area under at least a part of the signal, and a number of occurrences and/or a time of occurrence of zero crossings of the signal, identifying a dislocation of the stimulation electrode if a) the time of the signal is below a first threshold value and b) the morphologic parameter exceeds at least one further threshold value.

2. Implantable medical device according to claim 1, wherein the computer-readable program causes the processor to evaluate both the amplitude of the signal and the width of the signal.

3. Implantable medical device according to claim 1, wherein the computer-readable program causes the processor to wherein identify a dislocation of the stimulation electrode if a) the time of the signal is below a first threshold value and b) the absolute value of the amplitude of the signal traverses in two instances the further threshold value for the amplitude within a time exceeding the further threshold value for the width of the signal.

4. Implantable medical device according to claim 1, wherein the first threshold value is at least 80 ms.

5. Implantable medical device according to claim 1, wherein the further threshold value for the amplitude is at least 2 mV.

6. Implantable medical device according to claim 1, wherein 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 value for the amplitude.

7. Implantable medical device according to claim 1, wherein the at least one further threshold value is a relative value that is determined in relation to a signal amplitude of an R wave of at least one cardiac cycle preceding the evaluated signal.

8. Implantable medical device according to claim 1, wherein the first cardiac region is an atrium or a His bundle of a human or animal heart.

9. Implantable medical device according to claim 1, wherein the stimulation unit is configured and designed to apply an atrial antitachycardial stimulation to an atrium of a human or animal heart.

10. Implantable medical device according to claim 1, wherein the computer-readable program causes the processor to prevent a delivery of further stimulation pulses by the stimulation unit if a dislocation of the stimulation electrode has been identified.

11. Implantable medical device according to claim 1, wherein 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 a signal of an intracardiac electrogram and of identifying a dislocation of the stimulation electrode in a time window of 5 seconds to 30 seconds prior to an intended stimulation of the first cardiac region.

12. Implantable medical device according to claim 1, wherein 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.

13. Method for determining a dislocation of a stimulation electrode of a stimulation unit of an implantable medical device for stimulating a human or animal heart, the stimulation unit being configured to stimulate a first cardiac region of a human or animal heart, the method comprising the following steps: delivering a stimulation pulse to a human or animal heart by a stimulation unit comprising a stimulation electrode; evaluating a time and at least one morphologic parameter of a signal of an intracardiac electrogram detected by a detection unit configured to detect an intracardiac electrogram at a second cardiac region of the same heart, the second cardiac region being a ventricle, wherein the signal has been caused in response to the stimulation pulse, wherein the at least one morphologic parameter is chosen from the group comprising of: an absolute value of an amplitude of the signal, a width of the signal, a positive and/or a negative and/or a total area under at least a part of the signal, and a number of occurrences and/or a time of occurrence of zero crossings of the signal, identifying a dislocation of the stimulation electrode if a) the time of the signal is below a first threshold value and b) the morphologic parameter exceeds at least one further threshold value.

14. Computer program product comprising computer-readable code that causes a processor to perform the following steps when executed on the processor: delivering a stimulation pulse to a human or animal heart by a stimulation unit comprising a stimulation electrode; evaluating a time and at least one morphologic parameter of a signal of an intracardiac electrogram detected by a detection unit configured to detect an intracardiac electrogram at a second cardiac region of the same heart, the second cardiac region being a ventricle, wherein the signal has been caused in response to the stimulation pulse, wherein the at least one morphologic parameter is chosen from the group comprising of: an absolute value of an amplitude of the signal, a width of the signal, a positive and/or a negative and/or a total area under at least a part of the signal, and a number of occurrences and/or a time of occurrence of zero crossings of the signal, identifying a dislocation of the stimulation electrode if a) the time of the signal is below a first threshold value and b) the morphologic parameter exceeds at least one further threshold value.

15. 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, wherein the implantable medical device comprises a processor, a memory unit, a stimulation unit comprising a stimulation electrode configured to stimulate a first cardiac region of a human or animal heart, the first cardiac region being an atrium of the heart, and a detection unit configured to detect an intracardiac electrogram at a second cardiac region of the same heart, the second cardiac region being a ventricle, the method comprising the following steps: delivering a stimulation pulse to a human or animal heart by the stimulation unit; evaluating a time and at least one morphologic parameter of a signal of an intracardiac electrogram detected by the detection unit, wherein the signal has been caused in response to the stimulation pulse, wherein the at least one morphologic parameter is chosen from the group comprising of: an absolute value of an amplitude of the signal a width of the signal a positive and/or a negative and/or a total area under at least a part of the signal, and a number of occurrences and/or a time of occurrence of zero crossings of the signal, identifying a dislocation of the stimulation electrode if a) the time of the signal is below a first threshold value and b) the morphologic parameter exceeds at least one further threshold value; delivering stimulation pulses for an atrial antitachycardial stimulation to the human or animal heart by the stimulation unit, if no dislocation of the stimulation electrode was identified in the preceding step, or preventing delivering stimulation pulses for an atrial antitachycardial stimulation to the human or animal heart by the stimulation unit, if a dislocation of the stimulation electrode was identified in the preceding step.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0064] 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:

[0065] FIG. 1A shows a schematic depiction of a human heart with a correctly positioned atrial stimulation electrode;

[0066] FIG. 1B shows a schematic depiction of human heart with a dislocated atrial stimulation electrode;

[0067] FIG. 2 shows a first exemplary intracardiac electrogram representative for a correctly located atrial stimulation electrode;

[0068] FIG. 3 shows a second exemplary intracardiac electrogram representative for a correctly located atrial stimulation electrode;

[0069] FIG. 4 shows a third exemplary intracardiac electrogram representative for a dislocated atrial stimulation electrode; and

[0070] FIG. 5 shows a fourth exemplary intracardiac electrogram representative for a dislocated atrial stimulation electrode.

DETAILED DESCRIPTION

[0071] FIG. 1A shows a cardiac pacemaker 1 serving as an implantable medical device for stimulating a human or animal heart. This cardiac pacemaker 1 comprises a processor 101, a memory unit 102 connected to the processor 101, a stimulation electrode 2 forming part of a stimulation unit, as well as a sensing electrode 3 forming part of a detection unit. The stimulation electrode 2 is located within an atrium 4 of a human heart 5 to be stimulated. The sensing electrode 3 is located in a ventricle 6 of the same heart 5.

[0072] The sensing electrode 3 serves for detecting an intracardiac electrogram 7 comprising ventricular signals such as ventricular depolarizations.

[0073] 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.

[0074] FIG. 1B shows a similar situation, wherein the same or similar elements are denoted in this and all following Figures with the same numeral references. In the situation displayed in FIG. 1B, the stimulation electrode 2 is dislocated so that it no longer contacts atrial tissue in the atrium 4 of the human heart 5 to be stimulated, but rather ventricular tissue in the ventricle 6 of the heart 5.

[0075] 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.

[0076] FIG. 2 shows a first exemplary intracardiac electrogram 7 comprising a morphologic signal response to an atrial stimulation (pacing) pulse. This intracardiac electrogram has been recorded with a ventricular electrode after an atrial pace / ventricular pace stimulation sequence. In this case, the atrial stimulation electrode is correctly fixed within the atrium, wherein the ventricular electrode is fixed within the apex of the right ventricle of the heart to be stimulated. After a stimulation by the atrial electrode, no immediate signal can be detected by the ventricular electrode within 120 ms after the atrial stimulation pulse. Only after a ventricular stimulation (approximately at 130 ms), a typical signal response 9 after ventricular capture can be observed.

[0077] FIG. 3 shows a second exemplary electrocardiogram 7 comprising a morphologic signal response recorded at a ventricular electrode after an atrial pacing / ventricular sensing sequence. Also in this case, the atrial electrode is correctly positioned within the atrium. Likewise, the ventricular electrode is fixed within the apex of the right ventricle. In response to the stimulation with the atrial stimulation electrode, no immediate signal response can be observed within 140 ms after the atrial stimulation pulse. Only after an intrinsic transmission of the atrial stimulation into the ventricle, a typical signal response 9 for an intrinsic ventricular depolarization can be observed at approximately 160 ms.

[0078] FIG. 4 shows a third exemplary intracardiac electrogram 7 comprising a morphologic signal response recorded at a ventricular electrode after pacing with an atrial electrode. In this case, the atrial electrode is not correctly positioned within the atrium of the heart to be stimulated, but has rather been dislocated into the ventricle of the heart. Here, it is located in a high-septal position. The stimulation with the stimulation electrode results in an immediate ventricular signal 9 at less than 40 ms. Such an early response is typically for an intrinsic ventricular stimulation that can, however, be allocated to the stimulation by the atrial electrode due to its early occurrence after the stimulation pulse with the atrial stimulation electrode. Since the ventricular signal 9 exceeds a set threshold for the amplitude 12 and occurs prior to a set threshold value 11 for the time, it is considered as indication that the atrial stimulation electrode has been dislocated.

[0079] A similar situation is depicted in FIG. 5 showing another intracardiac electrogram 7 comprising a morphologic signal response recorded at a ventricular electrode after pacing with an atrial electrode. In this case, the atrial electrode has been dislocated into the ventricle and is now located at an apical position. After stimulation with the stimulation electrode, a signal response 9 can be detected at less than 20 ms that can be allocated as ventricular depolarization responsive to a ventricular stimulation pulse delivered by the atrial stimulation electrode. Since an absolute value of the ventricular signal 9 once again exceeds a threshold of 2 mV used as threshold value 12 for the amplitude and - at the same time -occurs earlier than a set threshold 11 for the time, also this ventricular signal 9 is considered as indicator for a dislocation of the atrial stimulation electrode.

[0080] Summarizing, ventricular signal responses to an atrial stimulation as shown in FIGS. 2 and 3 are indicative for a correctly positioned atrial stimulation electrode. In contrast, ventricular responses to a stimulation with a stimulation electrode as shown in FIGS. 4 and 5 are indicative for a dislocated atrial stimulation electrode. At least the amplitude and a temporal correlation with the stimulation pulse are used to distinguish between a correctly positioned stimulation electrode and a dislocated stimulation electrode. Further morphologic parameters like a signal which can also be used for making such decision.

[0081] 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.