DYNAMIC PATIENT-SPECIFIC FILTERING OF AN ACTIVITY SIGNAL WITHIN A BEATING HEART

• US 20160144191A1
• Filed: 11/25/2014
• Published: 05/26/2016
• Est. Priority Date: 11/25/2014
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Sheldon, Todd J., Demmer, Wade M., Kleckner, Karen J., Peterson, Douglas A., Solheim, Paul R.
• Granted Patent: US 9,724,518 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61N 1/36128 Control systems
• CPC Class Codes: A61N 1/36542 controlled by body motion, e.g. acceleration
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters

Abstract

An implantable medical device includes an activity sensor, a pulse generator, and a control module. The control module is configured to determine activity metrics from the activity signal and determine an activity metric value at a predetermined percentile of the activity metrics. The control module sets a lower pacing rate set point based on the activity metric value at the predetermined percentile.

Claims

1. A method for controlling a pacing rate by an implantable medical device, comprising:

sensing an activity signal correlated to a metabolic demand of the patient;

determining a first plurality of activity metrics from the activity signal;

determining an activity metric value at a predetermined percentile of the first plurality of activity metrics;

setting a lower rate set point based on the activity metric value at the predetermined percentile;

determining a next activity metric from the activity signal; and

delivering cardiac pacing at a lower base pacing rate in response to at least the next activity metric being less than or equal to the lower rate set point.

2. The method of claim 1, further comprising receiving the predetermined percentile by a wireless telemetry module of the implantable medical device as a programmable patient activity percentile.

3. The method of claim 1, further comprising:

determining a second plurality of activity metrics from the activity signal;

determining a first total number of the second plurality of activity metrics that are greater than the lower rate set point;

comparing the first total number of the second plurality of activity metrics that are greater than the lower rate set point to adjustment criteria; and

adjusting the lower rate set point in response to the first total number of the second plurality of activity metrics meeting the adjustment criteria.

4. The method of claim 3, wherein comparing the first total number of the second plurality of activity metrics to the adjustment criteria comprises comparing the first total number to a first expected number of the second plurality of activity metrics expected to be greater than the lower rate set point.

5. The method of claim 4, wherein adjusting the lower rate set point comprises adjusting the lower rate set point by one of a scaled increment and a scaled decrement based on a difference between the first total number and the first expected number.

6. The method of claim 4, further comprising:

determining a second total number of activity metrics of the second plurality of activity metrics that are greater than a second threshold that is greater than the lower rate set point;

comparing the second total number of activity metrics to a second expected number of the second plurality of activity metrics expected to be greater than the second threshold;

increasing the lower rate set point by a first increment in response to the first total number of the second plurality of activity metrics being greater than the first expected number and the second total number of activity metrics being less than the second expected number; and

increasing the lower rate set point by a second increment greater than the first increment in response to the second total number of activity metrics being greater than the second expected number.

7. The method of claim 4, further comprising:

determining a second total number of activity metrics of the second plurality of activity metrics that are greater than a second threshold that is less than the lower rate set point;

comparing the second total number of activity metrics to a second expected number of the second plurality of activity metrics expected to be greater than the second threshold;

decreasing the lower rate set point by a first decrement in response to the first total number of the second plurality of activity metrics being less than the first expected number and the second total number of activity metrics being at least the second expected number; and

decreasing the lower rate set point by a second decrement greater than the first decrement in response to the second total number of activity metrics being less than the second expected number.

8. The method of claim 1, wherein:

determining the first plurality of activity metrics comprises determining a series of activity metrics during each one of a plurality sampling periods during a first time interval;

determining the activity metric value comprises determining an activity metric value at the predetermined percentile of the series of activity metrics for each one of the plurality of sampling periods; and

setting the lower rate set point comprises adjusting the lower rate set point at the expiration of each one of the plurality of sampling intervals to the activity metric value determined for the respective one of the plurality of sampling intervals.

9. The method of claim 8, further comprising:

determining a second plurality of activity metrics during a second time interval following the first time interval;

determining an activity metric value at the predetermined percentile of the second plurality of activity metrics at the expiration of the second time interval; and

adjusting the lower rate set point to the activity metric value determined at the expiration of the second time interval.

10. The method of claim 1, wherein:

determining the first plurality of activity metrics comprises determining a series of activity metrics during each one of a plurality sampling periods during a first time interval;

determining the activity metric value comprises determining an activity metric value at the predetermined percentile of the series of activity metrics for each one of the plurality of sampling periods;

storing the activity metric value determined for each one of the plurality of sampling periods as an updated activity metric value at the expiration of each of the plurality of sampling periods; and

setting the lower rate set point comprises setting the lower rate set point at the expiration of the first time interval to a most recent updated activity metric value.

11. The method of claim 1, wherein determining the activity metric comprises determining an activity count by counting a number of times the activity sensor signal crosses a threshold during a predetermined counting time interval.

12. The method of claim 1, further comprising determining a sensor indicated pacing rate in response to at least the next activity metric, wherein the sensor indicated pacing rate is a lower base pacing rate if at least the next activity metric is less than or equal to the lower rate set point.

13. An implantable medical device, comprising:

an activity sensor configured to produce a signal correlated to a metabolic demand of a patient;

a pulse generator configured to generate and deliver pacing pulses to a patient'"'"'s heart via a pair of electrodes coupled to the implantable medical device; and

a control module coupled to the pulse generator and the activity sensor and configured to;

determine a first plurality of activity metrics from the activity sensor signal,

determine an activity metric value at a predetermined percentile of the first plurality of activity metrics,

set a lower rate set point based on the activity metric value at the predetermined percentile,

determine a next activity metric from the activity sensor signal, and

control the pulse generator to deliver cardiac pacing pulses at a lower base pacing rate in response to at least the next activity metric being less than or equal to the lower rate set point.

14. The device of claim 13, further comprising a wireless telemetry module coupled to the control module and configured to receive the predetermined percentile as a programmable patient activity percentile.

15. The device of claim 13, wherein the control module is further configured to:

determine a second plurality of activity metrics from the activity sensor signal;

determine a first total number of the second plurality of activity metrics that are greater than the lower rate set point;

compare the first total number of the second plurality of activity metrics that are greater than the lower rate set point to adjustment criteria; and

adjust the lower rate set point in response to the first total number of the second plurality of activity metrics meeting the adjustment criteria.

16. The device of claim 13, wherein the control module is configured to compare the first total number of the second plurality of activity metrics to the adjustment criteria by comparing the first total number to a first expected number of the second plurality of activity metrics expected to be greater than the lower rate set point.

17. The device of claim 16, wherein the control module is configured to adjust the lower rate set point by adjusting the lower rate set point by one of a scaled increment and a scaled decrement based on a difference between the first total number and the first expected number.

18. The device of claim 16, wherein the control module is further configured to:

determine a second total number of activity metrics of the second plurality of activity metrics that are greater than a second threshold that is greater than the lower rate set point;

compare the second total number of activity metrics to a second expected number of the second plurality of activity metrics expected to be greater than the second threshold;

increase the lower rate set point by a first increment in response to the first total number of the second plurality of activity metrics being greater than the first expected number and the second total number of activity metrics being less than the second expected number; and

increase the lower rate set point by a second increment greater than the first increment in response to the second total number of activity metrics being greater than the second expected number.

19. The device of claim 16, wherein the control module is further configured to:

determine a second total number of activity metrics of the second plurality of activity metrics that are greater than a second threshold that is less than the lower rate set point;

compare the second total number of activity metrics to a second expected number of the second plurality of activity metrics expected to be greater than the second threshold;

decrease the lower rate set point by a first decrement in response to the first total number of the second plurality of activity metrics being less than the first expected number and the second total number of activity metrics being at least the second expected number; and

decrease the lower rate set point by a second decrement greater than the first decrement in response to the second total number of activity metrics being less than the second expected number.

20. The device of claim 13, wherein the control module is further configured to:

determine the first plurality of activity metrics by determining a series of activity metrics during each one of a plurality sampling periods during a first time interval;

determine the activity metric value by determining an activity metric value at the predetermined percentile of the series of activity metrics for each one of the plurality of sampling periods; and

set the lower rate set point by adjusting the lower rate set point at the expiration of each one of the plurality of sampling intervals to the activity metric value determined for the respective one of the plurality of sampling intervals.

21. The device of claim 20, further comprising:

determine a second plurality of activity metrics during a second time interval following the first time interval;

determine an activity metric value at the predetermined percentile of the second plurality of activity metrics at the expiration of the second time interval; and

adjust the lower rate set point to the activity metric value determined at the expiration of the second time interval.

22. The device of claim 13, wherein the control module is further configured to:

determine the first plurality of activity metrics by determining a series of activity metrics during each one of a plurality sampling periods during a first time interval;

determine the activity metric value by determining an activity metric value at the predetermined percentile of the series of activity metrics for each one of the plurality of sampling periods;

store the activity metric value determined for each one of the plurality of sampling periods as an updated activity metric value at the expiration of each of the plurality of sampling periods; and

set the lower rate set point by setting the lower rate set point at the expiration of the first time interval to a most recent updated activity metric value.

23. The device of claim 13, wherein the control module is configured to determine the activity metric by determining an activity count by counting a number of times the activity sensor signal crosses a threshold during a predetermined counting time interval.

24. The device of claim 13, wherein the control module is further configured to determine a sensor indicated pacing rate in response to at least the next activity metric, wherein the sensor indicated pacing rate is the lower base pacing rate if at least the next activity metric is less than or equal to the lower rate set point.

25. The device of claim 13 further comprising a housing enclosing at least the control module and the pulse generator, wherein at least one of the pair of electrodes is along the housing.

26. A non-transitory, computer readable storage medium storing a set of instructions that, when executed by a control module of an implantable medical device, cause the device to:

sense an activity signal correlated to a metabolic demand of the patient;

determine a first plurality of activity metrics from the activity signal;

determine an activity metric value at a predetermined percentile of the first plurality of activity metrics;

set a lower rate set point based on the activity metric value at the predetermined percentile;

determine a next activity metric from the activity signal; and

deliver cardiac pacing pulses at a lower base pacing rate in response to at least the next activity metric being less than or equal to the lower rate set point.