Devices and methods for adjusting pacing rates in an implantable medical device

• US 10,065,041 B2
• Filed: 10/07/2016
• Issued: 09/04/2018
• Est. Priority Date: 10/08/2015
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Huelskamp, Paul, Kane, Michael J., Gifford, Douglas J.
• Primary Examiner(s): VOORHEES, CATHERINE M
• Application Number:
  US15/288,500
• Publication Number:
  US 20170100594A1
• Time in Patent Office: 697 Days
• CPC Class Codes: A61N 1/3621 for treating or preventing abnormally high heart rate
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy
• CPC Class Codes: A61N 1/365 controlled by a physiological parameter, e.g. heart potential evoked response A61N1/371
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/36542 controlled by body motion, e.g. acceleration
• CPC Class Codes: A61N 1/3756 Casings with electrodes thereon, e.g. leadless stimulators

Abstract

Systems, devices, and methods are disclosed for limiting the duration of elevated pacing rates in an implantable medical device. An illustrative device may include a housing, a plurality of electrodes connected to the housing, and a controller within the housing and connected to the electrodes. The controller may deliver pacing pulses to the electrodes at a base pacing rate, detect a measure of elevated metabolic demand which may vary over time, deliver pacing pulses at an elevated pacing rate based on the measure of elevated metabolic demand. The controller may change a heart stress tracking value (HSTV) when the pacing rate is elevated and may be changed faster during times of relatively higher elevated pacing rates than times of relatively lower elevated pacing rates. The elevated pacing rate may be reduced back toward the base pacing rate after the HSTV crossed a predetermined heart stress threshold.

Claims

1. A Leadless Cardiac Pacemaker (LCP) comprising:

an outer housing;

a plurality of exposed electrodes connected relative to the outer housing; and

a controller disposed within the outer housing and operatively connected to the plurality of exposed electrodes, wherein the controller is configured to;

deliver pacing pulses via the plurality of exposed electrodes at a base pacing rate;

detect a measure of metabolic demand, wherein the measure of metabolic demand varies over time;

deliver pacing pulses at an elevated pacing rate relative to the base pacing rate after determining an elevated metabolic demand with respect to a base measure of metabolic demand, wherein the elevated pacing rate varies with time and is dependent on the detected measure of metabolic demand;

adjust a heart stress tracking value during times when pacing pulses are delivered at the elevated pacing rate, wherein the heart stress tracking value is adjusted faster during times when higher elevated pacing rates are delivered relative to times when lower elevated pacing rates are delivered; and

determine when the heart stress tracking value crosses a predetermined heart stress threshold, and when the heart stress tracking value crosses the predetermined stress threshold, reducing the elevated pacing rate back toward the base pacing rate.

2. The LCP of claim 1, wherein the controller is configured to increase the heart stress tracking value monotonically over time.

3. The LCP of claim 1, wherein the controller is configured to decrease the heart stress tracking value monotonically over time.

4. The LCP of claim 1, wherein the controller is configured to deliver pacing pulses at the base pacing rate when the measure of metabolic demand is no longer elevated with respect to the base measure of metabolic demand.

5. The LCP of claim 1, wherein the controller is configured to reset the heart stress tracking value when the pacing pulses are no longer being delivered at the elevated pacing rate for at least a predetermined length of time.

6. The LCP of claim 1, wherein the controller is further configured to pause adjusting the heart stress tracking value when the elevated pacing rate falls below a threshold pacing rate that is higher than the base pacing rate.

7. The LCP of claim 1, further comprising an accelerometer disposed within the outer housing, and wherein the controller is configured to detect the measure of metabolic demand at least in part by monitoring an output of the accelerometer.

8. The LCP of claim 1, wherein the controller is configured to detect the measure of metabolic demand at least in part by monitoring an impedance signal via the plurality of exposed electrodes.

9. The LCP of claim 8, wherein the impedance signal provides a measure of respiration rate.

10. The LCP of claim 1, wherein the controller is configured to reduce the elevated pacing rate to the base pacing rate when the heart stress tracking value crosses the predetermined heart stress threshold.

11. The LCP of claim 10, wherein the base pacing rate is a lower rate limit.

12. The LCP of claim 10, wherein a counter is used to adjust the heart stress tracking value during times when pacing pulses are delivered at the elevated pacing rate.

13. The LCP of claim 12, wherein the counter is incremented at a faster rate during times when higher elevated pacing rates are delivered relative to times when lower elevated pacing rates are delivered.

14. A method for adjusting a pacing rate of a medical device, the method comprising:

generating, by the medical device, pacing pulses at a pacing rate that varies over time based on a determined metabolic demand;

adjusting, by the medical device, a heart stress tracking value while generating pacing pulses at or above a first pacing rate, wherein a rate of adjustment of the heart stress tracking value is dependent on a current pacing rate;

determining, by the medical device, when the heart stress tracking value crosses a predetermined heart stress threshold;

after determining that the heart stress tracking value crossed the predetermined heart stress threshold, generating, by the medical device, pacing pulses at a second pacing rate, wherein the second pacing rate is lower than the first pacing rate.

15. The method of claim 14, further comprising resetting the heart stress tracking value, by the medical device, after generating pacing pulses at pacing rates below a pacing rate threshold that is below the first pacing rate for a predetermined amount of time.

16. An implantable medical device for generating pacing pulses to a heart of a patient, the implantable medical device comprising:

a plurality of electrodes for delivering pacing pulses to the heart of the patient;

a pulse generator operatively coupled to the plurality of electrodes, the pulse generator configured to;

generate pacing pulses at a current pacing rate;

deliver the pacing pulses to the plurality of electrodes; and

a controller operatively coupled to the pulse generator, the controller comprising;

a pacing rate circuit configured to determine the current pacing rate for the pulse generator; and

a watchdog circuit configured to;

monitor the current pacing rate over time, and force the current pacing pulse of the pulse generator to be at a base pacing rate when the current pacing rate rises above a predetermined pacing rate threshold at a start time and remains above the predetermined pacing rate threshold for a predetermined threshold amount of time; and

when the current pacing rate falls below the predetermined pacing rate threshold before the predetermined threshold amount of time expires, and remains below the predetermined pacing rate threshold for at least a threshold amount of time, reset the start time at a next time the current pacing rate again rises above the predetermined pacing rate threshold.

17. The implantable medical device of claim 16, wherein after forcing the current pacing rate of the pulse generator to be at the base pacing rate, the watchdog circuit is configured to maintain the current pacing rate at the base pacing rate for at least a predetermined rest period of time.

18. The implantable medical device of claim 16, wherein the predetermined threshold amount of time is dependent on the current pacing rate while the current pacing rate remains above the predetermined pacing rate threshold.

19. The implantable medical device of claim 16, wherein the pacing rate circuit determines the current pacing rate in a rate responsive manner.

20. The implantable medical device of claim 16, wherein the implantable medical device is a leadless cardiac pacemaker configured to be implanted on or within a heart.