Implantable medical devices for stimulating the heart of a human or animal

Abstract

To provide an implantable medical device.SOLUTION: An implantable medical device for stimulating a human or animal heart comprises a control unit, a memory unit, a stimulation unit, and a detection unit for detecting an electrical signal of the same heart. The memory unit comprises a computer-readable program that causes the control unit to perform: a) a step 210 of detecting, with the detection unit, capture thresholds during an observation period, each capture threshold detected in response to a sequence of pacing pulses delivered by the stimulation unit; b) a step of storing the detected capture thresholds in the memory unit; and c) steps 230, 240 of decreasing a voltage U of a pacing output of the stimulation unit at most by a predetermined maximum value each day, where the voltage U of the pacing output remains at least as high as a maximum capture threshold determined within a time period equal to or shorter than the observation period.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an implantable medical device as recited in the preamble of claim 1, a method for controlling the operation of such an implantable medical device as recited in the preamble of claim 10, a computer program product as recited in the preamble of claim 11, and another implantable medical device as recited in the preamble of claim 13.

Background Art

[0002] Implantable medical devices for stimulating the heart of a human or animal, such as a cardiac pacemaker, typically use a capture control function to evaluate ventricular capture. Capture can be described as the success of ventricular stimulation, that is, it is defined as ventricular cardiac activity in response to an external or artificial stimulus (e.g., by a pacemaker).

[0003] The capture control function typically uses an algorithm that calculates the pacing output necessary to ensure capture while limiting the pacing output to minimize the power consumption of the implantable medical device. The capture control function periodically measures the capture threshold and automatically adjusts the pacing output using the following basic calculation (previous threshold + safety margin = pacing output).

[0004] Often, capture control is performed once a day, and the applied pacing output is decreased during a capture test to determine the capture threshold. Starting from a pacing output with a high amplitude, the amplitude of the pacing output is repeatedly decreased to determine the lowest amplitude that can still capture ventricular activity.

[0005] Traditional safety margin algorithms add a constant margin to either the last measured threshold or the maximum threshold over the evaluation period. These methods typically result in a relatively high pacing output and thus require a relatively high power consumption.

[0006] WO2017 / 139197A1 describes a capture control method that calculates the difference between the minimum and maximum thresholds of multiple last determined thresholds in a rolling time window. The larger the determined difference, the higher the safety margin added to the determined capture threshold to determine the pacing output to be used. Thus, this method utilizes a variable safety margin added to the highest determined capture threshold in a rolling time window; the margin is high when the variance of the determined capture thresholds is large, and the safety margin is low when the variance of the determined capture thresholds is small.

[0007] U.S. Patent Application Publication 2014 / 0350623(A1) describes a method for identifying candidate pulse widths corresponding to the lowest pulse energy sufficient to achieve capture within a patient's cardiac tissue. The application of different safety margins is also described in this context.

[0008] U.S. Patent Application Publication 2016 / 0346552(A1) and U.S. Patent Application Publication 2018 / 0036547(A1) exemplify the application of threshold testing to a determined capture threshold and the application of a safety margin to determine the pacing output (stimulus amplitude). [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The object of the present invention is to provide an implantable medical device for stimulating the heart of a human or animal, which consumes less power than implantable devices known from the prior art, while still guaranteeing a high level of patient safety in terms of cardiac capture. [Means for solving the problem]

[0010] This objective is achieved by an implantable medical device having the features of claim 1. Such an implantable medical device is intended to stimulate the heart of a human or animal. It comprises a control unit, a memory unit, a stimulating unit for stimulating a cardiac region of the human or animal heart, and a detection unit for detecting electrical signals from the same heart. In this context, the detection unit typically detects ventricular signals from the heart. The stimulating unit can stimulate the atria or ventricles of the human or animal heart. Often, the stimulating unit is intended to stimulate the right ventricle of the patient's heart.

[0011] According to the currently claimed invention, the storage unit includes a computer-readable program that, when executed on the control unit, causes the control unit to perform the steps described below.

[0012] In the first step, the capture threshold is detected using a detection unit. This detection is performed during the observation period. In this context, each capture threshold is detected in response to a sequence of pacing pulses delivered by a stimulation unit. Thus, the detection unit detects cardiac activity in response to an external or artificial stimulus.

[0013] The detected capture threshold is stored in the memory unit. Typically, time information is stored along with the capture threshold. This allows for easy retrieval of the time when a particular capture threshold is detected.

[0014] The threshold difference is determined between each pair of two consecutive capture thresholds. At least two capture thresholds are required for such a determination. Once the first and second capture thresholds are detected, the threshold-to-threshold difference between the first and second capture thresholds can be calculated. Then, once a third capture threshold is determined, the threshold-to-threshold difference between the second and third capture thresholds can be calculated. For example, with a capture threshold of 30, a threshold-to-threshold difference of 29 occurs between two consecutive capture thresholds in each case.

[0015] The calculated inter-threshold difference is then further evaluated. For this purpose, the maximum inter-threshold difference determined within the observation period is identified. If this maximum inter-threshold difference is equal to or greater than a given limit value, this indicates that the inter-threshold variety is rather large, and a higher pacing output is required to safely ensure ventricular capture. Therefore, in this option, the pacing output of the stimulation unit is adjusted based on the maximum capture threshold determined within the first period. In this context, the first period is equal to or shorter than the observation period.

[0016] On the other hand, if the difference between maximum determined thresholds within the observation period is smaller than a predetermined limit, this indicates that the variability between individual thresholds is relatively small. Next, it is also possible to guarantee cardiac capture by relying solely on the maximum amplitude over a period shorter than the first period. Thus, in this option, the pacing output of the stimulation unit is adjusted based on the maximum capture threshold determined within a second period, which is shorter than the first period.

[0017] It should be understood that the first and second periods extend back to the time when the pacing output of the stimulation unit was adjusted. Thus, the first period covers a larger capture threshold and therefore a larger inter-threshold difference than the second period, and both the first and second periods cover the most recent inter-threshold difference prior to the adjustment of the pacing output of the stimulation unit.

[0018] This dynamic aspect of the algorithm used by a computer-readable program provides an opportunity for energy saving that takes into account the power-to-safety trade-off associated with the length of the maximum threshold evaluation period, i.e., the first or second period. Increasing the evaluation period that tracks the maximum measurable capture threshold significantly increases the overall average pace output amplitude. However, the dynamic performance reduces the overall average pace output amplitude during the period when the capture threshold is stable by shortening this maximum capture threshold evaluation period to a second period.

[0019] The first and second periods are rolling window periods, which always end when the pacing output of the stimulation unit is adjusted in a manner used by a computer-readable program. Thus, the end point of this period always moves forward in time. Similarly, if the period itself is not extended, the start point of each period also moves forward in time. Thus, the implantable medical device currently claimed is a device that supports capture threshold processing, including storage of capture thresholds using a rolling window, measurement of maximum thresholds, and measurement of inter-threshold variability.

[0020] In one embodiment, the implantable medical device is an intracardiac device. The device is capable of delivering stimuli to cardiac tissue and measuring the capture thresholds for cardiac capture or ventricular capture, respectively.

[0021] In contrast to prior art solutions, the method used by the implantable medical device currently claimed measures the patient's maximum capture threshold and uses a novel measure of threshold stability to determine how long the capture threshold evaluation period should be tracked in order to determine pacing output based on this maximum capture threshold. This allows for faster dynamic responses during periods of stable capture thresholds, which reduce overall pacing output, while maintaining safety through longer windows during periods of unstable capture thresholds.

[0022] In one embodiment, the progress of the capture threshold is evaluated. In this embodiment, the stored capture threshold is used, for example, to assess whether there is a risk of undesirable dissociation of the implanted medical device from cardiac tissue. If a continuous increase in the capture threshold is detected, this may indicate that the implanted medical device is about to dissociate from cardiac tissue. In such a case, counteraction can be taken immediately to ensure safe implantation of the implanted medical device at the intended site of implantation. Thus, in this embodiment, patient safety is improved. If the capture threshold first increases, then decreases, and then increases or decreases again, this can be seen as indicating that there is no dissociation of the implanted medical device from the implantation site, and rather reflects natural fluctuations in the capture threshold.

[0023] In one embodiment, the step of detecting a capture threshold using a detection unit is performed once a day. For this purpose, typically multiple measurements are required, during which the pacing output used to stimulate cardiac tissue is repeatedly reduced. The capture threshold is the last value of the pacing output at which capture can be determined, and a first pacing output that fails to detect cardiac capture falls below the capture threshold.

[0024] In one embodiment, a computer-readable program causes a control unit to determine a pacing output by adding a safety margin to the maximum capture threshold, and the pacing output is adjusted based on the maximum capture threshold. Such a safety margin ensures cardiac capture even if there are other small variations in the capture threshold. Thus, such a safety margin improves patient safety, even if it consumes somewhat more energy than the operation without the safety margin. In other words, the safety margin ensures that cardiac capture occurs through stimulation by a pacing output resulting from adding a safety margin to a predetermined maximum capture threshold for a first or second period.

[0025] In one embodiment, the computer-readable program causes the control unit to set a safety margin without depending on the determined threshold difference or alternatively or further without depending on the determined maximum capture threshold. Thus, in contrast to prior art solutions that depend on variations in the safety margin applied to a specific maximum capture threshold to determine the final pacing output, this embodiment of the currently claimed invention rather depends on a skilled selection of the maximum threshold applied to calculate the pacing output, without varying the safety margin. As already outlined, the currently claimed approach better reflects the patient's physiological needs, and the patient's heart is stimulated by the implantable medical device while simultaneously saving a significant amount of energy required to pace the patient's heart. The approach employed by the currently described invention does not require a variable safety margin. Rather, the safety margin can be kept constant over the entire life of the implantable medical device or at least over substantially the entire life of the implantable medical device.

[0026] In one embodiment, the computer-readable program causes the control unit to set a higher safety margin during a third period than after the third period. In this context, the third period is the period immediately after implantation of the implantable medical device. This embodiment takes into account that the capture threshold typically is somewhat higher and more variable during the first week after implantation and then decreases to a relatively constant value that is typically lower. Thus, combining the previous embodiment with this embodiment, the safety margin changes only during the very first time after implantation and is kept constant for the remaining life of the implantable medical device. This can be regarded as a constant safety margin over substantially the entire life of the implantable medical device. In one embodiment, the term "substantially the entire life of the implantable medical device" should be interpreted to mean the entire life minus the third period (regardless of any variations in the safety margin during the third period).

[0027] In one embodiment, the third period is a period that spans from 1 to 200 days, particularly from 5 to 190 days, particularly from 10 to 180 days, particularly from 20 to 170 days, particularly from 30 to 160 days, particularly from 40 to 150 days, particularly from 50 to 140 days, particularly from 60 to 130 days, particularly from 70 to 120 days, particularly from 80 to 110 days, and particularly from 90 to 100 days. In any case, the third period begins immediately after the implantation of the implantable medical device, particularly the implantation of the implantable medical device into the patient's heart.

[0028] In one embodiment, the implantable medical device is a leadless pacemaker. The leadless pacemaker is implanted in the patient's heart; that is, they can also be referred to as intracardiac devices. Leadless pacemakers are typically smaller than conventional pacemakers, and therefore require less space for energy sources such as batteries. Consequently, the power consumption of a leadless pacemaker is much better controlled than that of a conventional pacemaker. Therefore, leadless pacemakers are a very interesting area for application of the currently claimed invention, as the current claimed invention can significantly extend the lifespan of leadless pacemakers and thus make such devices even more attractive than those already in use.

[0029] In one embodiment, the computer-readable program causes the control unit to reduce the voltage of the pacing output by at most a predetermined maximum value each day. When this embodiment is applied, the initial voltage of the pacing output is more restricted than the potentially possible range according to the determined capture threshold and the threshold difference. Therefore, the operation of the implantable medical device according to this embodiment results in higher energy consumption than is absolutely necessary. However, further, the safety of the patient is improved. Further, the predetermined maximum value by which the voltage of the pacing output can be reduced by at most that amount each day can be set so that the period during which the energy consumption of the implantable medical device becomes unnecessarily high is limited to several days or weeks. By doing so, during the first period of operation of the implantable medical device, for example, immediately after implantation, the pacing output can be set to a high level. As a further example, during the third period, the decrease in the voltage of the pacing output can be limited and used. Thereafter, even if the patient's heart tissue has not yet been finally affected by the stimulation by the pacing pulse, a fairly high pacing output for realizing cardiac capture can be ensured.

[0030] In one embodiment, the predetermined maximum value of the step-down size is in the range of 0.05 V to 0.2 V, particularly 0.075 V to 0.15 V, particularly 0.1 V to 0.12 V.

[0031] In one embodiment, the observation period and / or the first period is a period ranging from 7 days to 50 days, particularly 10 days to 45 days, particularly 15 days to 40 days, particularly 20 days to 35 days, particularly 25 days to 30 days. In one embodiment, the first period has the same length as the observation period, that is, the first period is equal to the observation period. For example, the observation period extends for 30 days. Next, the first period extends for the 30 days immediately preceding the day when the pacing output of the stimulation unit is adjusted according to the method used by the currently claimed implantable medical device.

[0032] In one embodiment, the second period is a period of 2 to 14 days, particularly 3 to 13 days, particularly 4 to 12 days, particularly 5 to 11 days, particularly 6 to 10 days, and particularly 7 to 9 days. A particularly suitable second period is 2 to 6 days, for example, 3 days, 4 days, 5 days, or 6 days.

[0033] One aspect of the present invention relates to a method for controlling the operation of an implantable medical device for stimulating the heart of a human or animal as described above. This method includes the steps described below.

[0034] First, the electrical signals of a human or animal heart are detected using a detection unit. This detection helps in determining the capture threshold during the observation period. Each capture threshold is detected in response to a sequence of pacing pulses delivered by a stimulation unit to stimulate a cardiac region of the same heart.

[0035] The detected detection threshold is stored in the memory unit of the implantable medical device.

[0036] Furthermore, the threshold difference between two consecutive capture thresholds in each case is determined.

[0037] Subsequently, it is determined whether the difference between maximum determination thresholds within the observation period is equal to or greater than a predetermined limit (first option), or less than a predetermined limit (second option). In the first option, the pacing output of the stimulation unit is adjusted based on the maximum capture threshold determined within the first period. In this context, the first period is equal to or shorter than the observation period. In the second option, the pacing output of the stimulation unit is adjusted based on the maximum capture threshold determined within the second period. In this context, the second period is shorter than the first period. The first and second periods are periods extending back to the time when the pacing output of the stimulation unit was adjusted.

[0038] One aspect of the present invention relates to a computer program product comprising computer-readable code that, when executed on a control unit, causes a control unit to perform the following steps.

[0039] First, the electrical signals of a human or animal heart are detected using a detection unit. This detection helps in determining the capture threshold during the observation period. Each capture threshold is detected in response to a sequence of pacing pulses delivered by a stimulation unit to stimulate a cardiac region of the same heart.

[0040] The detected detection threshold is stored in the memory unit of the implantable medical device.

[0041] Furthermore, the threshold difference between two consecutive capture thresholds in each case is determined.

[0042] Subsequently, it is determined whether the difference between maximum determination thresholds within the observation period is equal to or greater than a predetermined limit (first option), or less than a predetermined limit (second option). In the first option, the pacing output of the stimulation unit is adjusted based on the maximum capture threshold determined within the first period. In this context, the first period is equal to or shorter than the observation period. In the second option, the pacing output of the stimulation unit is adjusted based on the maximum capture threshold determined within the second period. In this context, the second period is shorter than the first period. The first and second periods are periods extending back to the time when the pacing output of the stimulation unit was adjusted.

[0043] One aspect of the present invention relates to a medical method for treating a human or animal patient requiring such treatment. This treatment is performed by an implantable medical device for stimulating the heart of a human or animal, particularly by an implantable medical device as described above. Such an implantable medical device comprises a control unit, a memory unit, a stimulation unit for stimulating a cardiac region of the human or animal heart, and a detection unit for detecting electrical signals from the same heart. This method includes the steps described below.

[0044] First, the electrical signals of a human or animal heart are detected using a detection unit. This detection helps in determining the capture threshold during the observation period. Each capture threshold is detected in response to a sequence of pacing pulses delivered by a stimulation unit to stimulate a cardiac region of the same heart.

[0045] The detected detection threshold is stored in the memory unit of the implantable medical device.

[0046] Furthermore, the threshold difference between two consecutive capture thresholds in each case is determined.

[0047] Subsequently, it is determined whether the difference between maximum determination thresholds within the observation period is equal to or greater than a predetermined limit (first option), or less than a predetermined limit (second option). In the first option, the pacing output of the stimulation unit is adjusted based on the maximum capture threshold determined within the first period. In this context, the first period is equal to or shorter than the observation period. In the second option, the pacing output of the stimulation unit is adjusted based on the maximum capture threshold determined within the second period. In this context, the second period is shorter than the first period. The first and second periods are periods extending back to the time when the pacing output of the stimulation unit was adjusted.

[0048] Subsequently, the human or animal heart is stimulated by applying pacing pulses by the stimulation unit with the pacing output adjusted in the previous step. Therefore, the pacing pulses can have different amplitudes depending on the previously observed variability of the capture thresholds. Typically, the pacing pulses have a higher amplitude if the variability in the detected threshold differences is relatively large (i.e., the stimulation unit is operated with a higher pacing output). Conversely, the pacing pulses have a lower amplitude if the variability between individual capture thresholds is determined to be smaller, i.e., if the threshold differences are relatively small (i.e., the stimulation unit is operated with a lower pacing output).

[0049] Further aspects of the present invention are other implantable medical devices for stimulating the heart of a human or animal, which can be combined with any of the embodiments described above, but are claimed independently of the embodiments and examples described above. This further implantable medical device comprises a control unit, a memory unit, a stimulation unit for stimulating a cardiac region of the heart of a human or animal, and a detection unit for detecting electrical signals from the same heart.

[0050] The memory unit contains a computer-readable program that, when executed on the control unit, causes the control unit to perform the steps described below.

[0051] First, the capture threshold is detected using a detection unit during the observation period. In this context, each capture threshold is detected in response to a sequence of pacing pulses delivered by a stimulation unit.

[0052] The detected capture threshold is stored in the memory unit.

[0053] The voltage of the pacing output of the stimulation unit decreases by at most a predetermined maximum value each day. In this context, the voltage of the pacing output remains at least the same height as the maximum capture threshold determined within a period equal to or shorter than the observation period. According to one embodiment, the voltage of the pacing output remains at least the same height as the maximum capture threshold determined within a period equal to or shorter than the observation period with an added safety margin. In doing so, it is ensured that the applied voltage of the pacing output is always at least the same height as the determined capture threshold with an added safety margin, while at the same time ensuring that it decreases only in small steps from the previous value. This helps to deal with sudden drops in the capture threshold that may only be temporary. According to one embodiment of the present invention, a predetermined value is defined that represents the maximum value for a single drop in the pacing output, in particular.

[0054] In one embodiment, the limited reduction in the pacing output voltage is performed only over a predetermined period, for example, only during the third period as defined above.

[0055] In one embodiment, the predetermined maximum value is in the range of 0.05V to 0.2V, particularly 0.075V to 0.15V, and particularly 0.1V to 0.12V.

[0056] In one embodiment, the implantable medical device not only implements a limited reduction in the initial voltage of the pacing output but also adjusts the pacing output in response to the observed variation in the capture threshold. In this embodiment, a computer-readable program causes the control unit to adjust the pacing output of the stimulation unit according to either a first or second option. According to the first option, if the difference between maximum determined thresholds within the observation period is equal to or greater than a predetermined limit, the pacing output is adjusted based on the maximum capture threshold determined within the first period. In this context, the first period is equal to or shorter than the observation period. According to the second option, if the difference between maximum determined thresholds within the observation period is less than a predetermined limit, the pacing output of the stimulation unit is adjusted based on the maximum capture threshold determined within the second period. In this context, the second period is shorter than the first period.

[0057] Therefore, in this embodiment, the pacing output voltage decreases by a predetermined maximum value each day until it reaches the output of an algorithm that evaluates past capture threshold variability. This mode of operation ensures that cases that cannot be captured are avoided. However, if the output of the algorithm that evaluates past capture threshold variability results in a required capture threshold higher than the value obtained by subtracting the maximum value that the pacing output voltage has decreased to at most each day from the last pacing output voltage, the pacing output is immediately updated to the pacing output determined based on the maximum capture threshold determined by the algorithm.

[0058] One aspect of the present invention relates to a method for controlling the operation of an implantable medical device for stimulating the heart of a human or animal, the method comprising: a) detecting a capture threshold during an observation period using a detection unit for detecting electrical signals of the heart of a human or animal, wherein each capture threshold is detected in response to at least one pacing pulse or sequence of pacing pulses delivered by a stimulation unit for stimulating a cardiac region of the same heart; b) storing the detected capture thresholds in a memory unit of the implantable medical device; and c) reducing the voltage of the pacing output of the stimulation unit by at most a predetermined maximum value each day, such that the voltage of the pacing output remains at least the same as the maximum capture threshold determined within a period equal to or shorter than the observation period. According to one embodiment, the voltage of the pacing output remains at least the same as the maximum capture threshold determined within a period equal to or shorter than the observation period with an added safety margin.

[0059] One aspect of the present invention relates to a computer program product comprising computer-readable code that, when executed on a control unit, causes a control unit to perform the following steps: a) a detection unit for an implantable medical device for stimulating the heart of a human or animal, wherein the detection unit is configured to detect electrical signals of the heart of a human or animal, each capture threshold being detected in response to a pacing pulse delivered by a stimulating unit of the implantable medical device, the stimulating 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; and c) reducing the voltage of the pacing output of the stimulating unit by at most a predetermined maximum value each day, such that the voltage of the pacing output remains at least the same as the maximum capture threshold determined within a period equal to or shorter than the observation period. According to one embodiment, the voltage of the pacing output remains at least the same as the maximum capture threshold determined within a period equal to or shorter than the observation period with an added safety margin.

[0060] One aspect of the present invention relates to a method for treating a human or animal patient in need of such treatment using an implantable medical device for stimulating the heart of a human or animal, wherein the implantable medical device comprises a control unit, a memory unit, a stimulating unit for stimulating a cardiac region of the human or animal heart, and a detection unit for detecting electrical signals of the same heart, the method comprising: a) detecting capture thresholds during an observation period using the detection unit, wherein each capture threshold is detected in response to a pacing pulse delivered by the stimulating unit; b) storing the detected capture thresholds in the memory unit; c) reducing the voltage of the pacing output of the stimulating unit by at most a predetermined maximum value each day, such that the voltage of the pacing output remains at least the same as the maximum capture threshold determined within an observation period equal to or shorter than an observation period with an applied safety margin; and d) stimulating the heart of a human or animal by applying pacing pulses with the pacing output adjusted in the preceding steps.

[0061] All embodiments of the individual implantable medical devices described herein can be combined in any desired manner and adapted to each other implantable medical device, the described method, and the described computer program product. Furthermore, any embodiment of the described method can be combined in any desired manner and adapted to each other method, a different implantable medical device, and the described computer program product. Finally, any embodiment of the computer program product can be combined in any desired manner and adapted to each other computer program product, the described implantable medical device, and the described method in any combination.

[0062] Further details of aspects of the present invention will be described with reference to exemplary embodiments and accompanying drawings. [Brief explanation of the drawing]

[0063] [Figure 1] This is a schematic workflow of a first embodiment of a method for determining the pacing output of a stimulation unit in an implantable medical device. [Figure 2] This is a schematic workflow of a second embodiment of a method for determining the pacing output of a stimulation unit in an implantable medical device. [Modes for carrying out the invention]

[0064] Figure 1 shows the workflow of the method performed by a cardiac pacemaker as an implantable medical device. First, the detection unit of the cardiac pacemaker helps in the detection of capture thresholds 110 during the observation period. Subsequently, the determination of the inter-threshold difference 120 between two consecutive capture thresholds is performed.

[0065] Next, a determination 130 is made to determine whether the maximum threshold difference determined during the observation period is equal to, greater than, or less than a predetermined limit value. The limit value is then set to 0.4V in the embodiment shown in Figure 1. If the maximum determined threshold difference is at least 0.4V, a selection 140 of the maximum capture threshold for the past 30 days is performed. In this context, 30 days constitutes the first period. On the other hand, if the maximum determined threshold difference is less than 0.4V, a selection 150 of the maximum determined capture threshold for the past 3 days is performed. In this context, 3 days constitutes the second period. Subsequently, a safety margin 160 is added to the selected maximum capture threshold.

[0066] Finally, adjustment 170 of the pacing output for the pacing pulse from the stimulating unit of the implanted medical device is performed. This adjustment is based on the selected maximum capture threshold and defines the pacing output so that it is the sum of the selected capture threshold and a safety margin.

[0067] This method is typically applied once a day by a cardiac pacemaker.

[0068] The safety margin added to the maximum capture threshold selected in step 160 is selected to be 0.4V if the cardiac pacemaker has not been implanted for longer than a predetermined period since implantation, and is reduced to 0.3V if cardiac pacemaker implantation has been performed for longer than a predetermined period. In one embodiment, the predetermined 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.

[0069] Figure 2 shows a schematic workflow of a further method applied by another cardiac pacemaker, which serves as a further embodiment of an implantable medical device.

[0070] First, the determination of the capture threshold 210 is performed during the observation period. This detection is performed using the detection unit of the cardiac pacemaker. Each capture threshold is determined in response to a sequence of pacing pulses delivered by the stimulation unit of the cardiac pacemaker.

[0071] The capture threshold typically helps adjust the pacing output of a cardiac pacemaker. However, before adjusting the pacing output, a decision 220 is made regarding the reduction of the pre-applied pacing output. If the voltage U of the pre-applied pacing output reduced by 0.1V is at least the same height as the determined capture threshold CT (with an optional safety margin added), then a pacing output adjustment 230 is made for the pre-applied pacing output reduced by 0.1V.

[0072] However, if the determination 220 results in the detection 210 of the capture threshold (with an optional safety margin added) yielding a capture threshold CT higher than the pre-applied pacing output voltage U which is 0.1V lower, then the pacing output adjustment 240 is performed based on the determined capture threshold (the safety margin is optionally considered and added to the detected maximum capture threshold). In one embodiment, the pacing output is immediately increased to the output determined by the algorithm.

[0073] This method ensures that the pacing output is iteratively reduced by a maximum value, set to 0.1V in this embodiment, until it reaches the algorithm-determined pacing output. This method is implemented so that if the required capture threshold rises unexpectedly, the pacing output is automatically increased, ensuring that safe cardiac capture is always guaranteed.

[0074] Furthermore, even without repeated reductions of the previous pacing output, this method ensures that the applied pacing output never falls below the required capture threshold.

[0075] The embodiment shown in Figure 2 can be combined with the embodiment in Figure 1, or it can be implemented without using the embodiment in Figure 1 for the cardiac pace marker.

Claims

1. An implantable medical device for stimulating the heart of a human or animal, comprising a control unit, a memory unit, a stimulation unit for stimulating the cardiac region of the human or animal heart, and a detection unit for detecting electrical signals from the same heart, When the storage unit is executed on the control unit, a) Step (210) of detecting a capture threshold during the observation period using the detection unit, wherein each capture threshold is detected in response to a pacing pulse delivered by the stimulation unit, b) The step of storing the detected capture threshold in the storage unit, c) A step of determining a reduced voltage, wherein the reduced voltage is the voltage (U) of the pacing output of the stimulation unit, which is reduced each day by at most a predetermined maximum value, and if the reduced voltage is at least the same height as the maximum capture threshold determined within a period equal to or shorter than the observation period, the voltage (U) of the pacing output is adjusted to the reduced voltage, and if the reduced voltage is lower than the maximum capture threshold, the voltage (U) of the pacing output is increased to the maximum capture threshold. An implantable medical device characterized by including a computer-readable program that causes the control unit to execute the above.

2. The implantable medical device according to claim 1, characterized in that the predetermined maximum value is in the range of 0.05V to 0.2V.

3. The computer-readable program, with respect to the threshold difference between two consecutive capture thresholds, i) adjusts the pacing output of the stimulation unit based on the largest capture threshold in the first period if the largest threshold difference among the threshold differences determined within the observation period is equal to or greater than a predetermined limit value (140; 170), and ii) adjusts the pacing output of the stimulation unit based on the largest capture threshold in the second period if the largest threshold difference within the observation period is less than the predetermined limit value (150; 1 The implantable medical device according to claim 1 or 2, characterized in that the control unit is made to perform 70), the first period and the second period are periods extending from the time the pacing output of the stimulation unit was adjusted to the past, the first period is equal to or shorter than the observation period, the second period is shorter than the first period, the first period covers a larger threshold difference than the second period, and both the first period and the second period cover the most recent threshold difference before the pacing output of the stimulation unit is adjusted.

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