Implantable Medical Device for Stimulating a Human or Animal Heart

Abstract

An implantable medical device for stimulating a heart, comprising a control unit, a memory unit, a stimulation unit for stimulating a cardiac region of a heart, and a detection unit for detecting an electrical signal of the heart. The memory unit comprises a computer-readable program that causes the control unit to perform the following steps: a) detecting capture thresholds during an observation period, each capture threshold detected in response to a sequence of pacing pulses delivered by the stimulation unit; b) storing the detected capture thresholds in the memory unit; c) determining threshold-to-threshold differences between two consecutive capture thresholds; and d) if a maximum determined threshold-to-threshold difference within the observation period is equal to or greater than a predetermined limit, adjusting a pacing output of the stimulation unit based on the maximum capture threshold determined within a first time period which is equal to or shorter than the observation period.

Claims

1. Implantable medical device for stimulating a human or animal heart, comprising a control unit, a memory unit, a stimulation unit for stimulating a cardiac region of a human or animal heart, and a detection unit for detecting an electrical signal of the same heart, wherein the memory unit comprises a computer-readable program that causes the control unit to perform the following steps when executed on the control unit: a) detecting, with the detection unit, capture thresholds during an observation period, each capture threshold being detected in response to a sequence of pacing pulses delivered by the stimulation unit; b) storing the detected capture thresholds in the memory unit; c) determining threshold-to-threshold differences between two consecutive capture thresholds in each case; and d) if a maximum determined threshold-to-threshold difference within the observation period is equal to or greater than a predetermined limit, adjusting a pacing output of the stimulation unit on the basis of the maximum capture threshold determined within a first time period, the first time period being equal to or shorter than the observation period; or if the maximum determined threshold-to-threshold difference within the observation period is smaller than the predetermined limit, adjusting the pacing output of the stimulation unit on the basis of the maximum capture threshold determined within a second time period, the second time period being shorter than the first time period.

2. Implantable medical device according to claim 1, wherein the computer-readable program causes the control unit to determine the pacing output by adding a safety margin to the maximum capture threshold on the basis of which the pacing output is adjusted.

3. Implantable medical device according to claim 2, wherein the computer-readable program causes the control unit to set the safety margin independently on the determined threshold-to-threshold differences.

4. Implantable medical device according to claim 2, wherein the computer-readable program causes the control unit to set the safety margin during a third time period greater than after the third time period, the third time period being a time period starting with implantation of the implantable medical device.

5. Implantable medical device according to claim 1, wherein the implantable medical device is a leadless pacemaker.

6. Implantable medical device according to claim 1, wherein the computer-readable program causes the control unit to decrease a voltage of the pacing output at most by a predetermined maximum value each day.

7. Implantable medical device according to claim 6, wherein the predetermined maximum value lies in a range between 0.05 V and 0.2 V.

8. Implantable medical device according to claim 1, wherein the observation period and/or the first time period are a time period covering 7 days to 50 days.

9. Implantable medical device according to claim 1, wherein the second time period is a time period covering 2 days to 14 days.

10. (canceled)

11. Computer program product comprising computer-readable code that causes a control unit to perform the following steps when executed on the control unit: a) detecting, with a detection unit of an implantable medical device for stimulating a human or animal heart, the detection unit being configured to detect an electrical signal of a human or animal heart, capture thresholds during an observation period, each capture threshold being detected in response to a pacing pulse delivered by a stimulation unit of the implantable medical device, the stimulation unit being configured to stimulate a cardiac region of the same heart; b) storing the detected capture thresholds in a memory unit of the implantable medical device; c) determining threshold-to-threshold differences between two consecutive thresholds in each case; and d) if a maximum determined threshold-to-threshold difference within the observation period is equal to or greater than a predetermined limit, adjusting a pacing output of the stimulation unit on the basis of the maximum capture threshold determined within a first time period, the first time period being equal to or shorter than the observation period; or if the maximum determined threshold-to-threshold difference within the observation period is smaller than the predetermined limit, adjusting the pacing output of the stimulation unit on the basis of the maximum capture threshold determined within a second time period, the second time period being shorter than the first time period.

12. (canceled) .

13. Implantable medical device for stimulating a human or animal heart, comprising a control unit, a memory unit, a stimulation unit for stimulating a cardiac region of a human or animal heart, and a detection unit for detecting an electrical signal of the same heart, wherein the memory unit comprises a computer-readable program that causes the control unit to perform the following steps when executed on the control unit: a) detecting, with the detection unit, capture thresholds during an observation period, each capture threshold being detected in response to a pacing pulse delivered by the stimulation unit; b) storing the detected capture thresholds in the memory unit; c) decreasing a voltage (U) of a pacing output of the stimulation unit at most by a predetermined maximum value each day, wherein the voltage (U) of the pacing output remains at least as high as a maximum capture threshold determined within a time period being equal to or shorter than the observation period.

14. Implantable medical device according to claim 13, wherein the predetermined maximum value lies in a range between 0.05 V and 0.2 V.

15. Implantable medical device according to claim 13, wherein the computer-readable program causes the control unit to i) adjust the pacing output of the stimulation unit on the basis of the maximum capture threshold determined within a first time period, if a maximum determined threshold-to-threshold difference within the observation period is equal to or greater than a predetermined limit, the first time period being equal to or shorter than the observation period; or ii) adjust the pacing output of the stimulation unit on the basis of the maximum capture threshold determined within a second time period, if the maximum determined threshold-to-threshold difference within the observation period is smaller than the predetermined limit, the second time period being shorter than the first time period.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Further details of aspects of the present invention will be explained with respect to exemplary embodiments and accompanying Figures. In the Figures:

[0069] FIG. 1 shows a schematic workflow of a first embodiment of a method for determining a pacing output of a stimulation unit of an implantable medical device;

[0070] FIG. 2 shows a schematic workflow of a second embodiment of a method for determining a pacing output of a stimulation unit of an implantable medical device;

[0071] FIG. 3 shows a schematic representation of an implantable medical device of a first embodiment; and

[0072] FIG. 4 shows a schematic representation of an implantable medical device of a second embodiment.

DETAILED DESCRIPTION

[0073] FIG. 1 illustrates the workflow of a method implemented by a cardiac pacemaker as implantable medical device. First, a detection unit of the cardiac pacemaker serves for detecting 110 capture thresholds during an observation period. Afterwards, a determination 120 of threshold-to-threshold differences between two consecutive capture thresholds is carried out.

[0074] Then, a decision 130 takes place whether the maximum threshold-to-threshold difference determined within the observation period is either equal to or above a preset limit or below this limit. Thereby, the limit is set to be 0.4 V in the embodiment of FIG. 1. If the maximum determined threshold-to-threshold difference is at least 0.4 V, a selection 140 of the maximum capture threshold during the past 30 days takes place. In this context, 30 days serve as first time period. If, on the other hand, the maximum determined threshold-to-threshold difference is below 0.4 V, a selection 150 of the maximum determined capture threshold during the past 3 days takes place. In this context, 3 days serve as second time period. Afterwards, an addition 160 of a safety margin to the selected maximum capture threshold is carried out.

[0075] Finally, an adjustment 170 of a pacing output for a pacing pulse by a stimulation unit of the implantable medical device is performed. This adjustment is based on the selected maximum capture threshold and defines the pacing output to be the sum of the selected capture threshold and the safety margin.

[0076] This method is typically applied once a day by the cardiac pacemaker.

[0077] The safety margin added to the selected maximum capture threshold in step 160 is chosen to be 0.4 V in case that the cardiac pacemaker has been implanted no longer than a predefined period since implant and is reduced to 0.3 V in case that the implantation of the cardiac pacemaker has been carried out longer than the predefined time period. According to an embodiment, the predefined period is 20 to 150 days, or 50 to 120 days, or 70 to 120 days, or 90 to 120 days, or 100 to 120 days, or 112 days.

[0078] FIG. 2 shows a schematic workflow of a further method that is applied by another cardiac pacemaker, serving as further embodiment of an implantable medical device.

[0079] First, a determination 210 of capture thresholds takes place during an observation period. This detection is carried out with a detection unit of the cardiac pacemaker. Each capture threshold is determined in response to a sequence of pacing pulses delivered by a stimulation unit of the cardiac pacemaker.

[0080] The capture thresholds generally serve for adjusting a pacing output of the cardiac pacemaker. However, prior to adjusting the pacing output, a determination 220 takes place regarding a decrease of the previously applied pacing output. If a voltage U of the previously applied pacing output reduced by 0.1 V is at least as high as the determined capture threshold CT (optionally plus a safety margin), an adjustment 230 of the pacing output to the previously applied pacing output minus 0.1 V takes place.

[0081] If, however, the determination 220 gives the result that the detection 210 of the capture threshold (optionally plus a safety margin) resulted in a higher capture threshold CT than a voltage U of the previously applied pacing output reduced by 0.1 V, an adjustment 240 of the pacing output on the basis of the determined capture threshold takes place (a safety margin is optionally considered and added to the detected maximum capture threshold). According to an embodiment, the pacing output is immediately increased to the output determined by the algorithm.

[0082] This method guarantees that the pacing output is reduced in an iterative way by a maximum value which is set to 0.1 V in the present embodiment until the pacing output reaches the algorithm-determined pacing output. This method is performed such that an unforeseeable increase in the necessary capture threshold will automatically lead to an increase of the pacing output so that the safe cardiac capture can always be guaranteed.

[0083] Furthermore, even if no iterative decrease of a previous pacing output is done, the method guarantees that the applied pacing output never falls below the necessary capture threshold.

[0084] The embodiment shown in FIG. 2 can be combined with the embodiment of FIG. 1 or can be implemented without the embodiment of FIG. 1 in a cardiac pacemaker.

[0085] FIG. 3 shows a schematic representation of an implantable medical device 1 (e.g., a cardiac pacemaker) for stimulating a human or animal heart H, comprising a control unit 10 (e.g., a processor), a memory unit 12, a stimulation unit 14 for stimulating a cardiac region of a human or animal heart, and a detection unit 16 for detecting an electrical signal of the same heart H. The memory unit 12 comprises a computer-readable program that causes the control unit 10 to perform the steps of the workflow shown in FIG. 1 when executed on the control unit 10.

[0086] FIG. 4 shows a schematic representation of an implantable medical device 1′ (e.g., a cardiac pacemaker) for stimulating a human or animal heart H′, comprising a control unit 10′ (e.g., a processor), a memory unit 12′, a stimulation unit 14′ for stimulating a cardiac region of a human or animal heart H′, and a detection unit 16′ for detecting an electrical signal of the same heart H′. The memory unit 12′ comprises a computer-readable program that causes the control unit 10′ to perform the steps of the workflow shown in FIG. 2 when executed on the control unit 10′

[0087] 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 zo 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.