Cardiac rhythm management system with maximum tracking rate (MTR) hysteresis

• US 6,904,316 B2
• Filed: 11/06/2001
• Issued: 06/07/2005
• Est. Priority Date: 11/06/2001
• Status: Expired due to Term

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Kramer, Andrew P.
• Primary Examiner(s): Schaetzle, Kennedy
• Assistant Examiner(s): Mullen, Kristen
• Application Number:
  US10/012,887
• Publication Number:
  US 20030088287A1
• Time in Patent Office: 1,309 Days
• Field of Search: 607/4, 607/9, 607/14, 607/15, 607/17, 607/25
• US Class Current: 607/9
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions
• 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 1/3684 for stimulating the heart at multiple sites of the ventricle or the atrium
• CPC Class Codes: A61N 1/36843 Bi-ventricular stimulation

Abstract

A cardiac rhythm management system provides both a safe maximum pacing rate limit and a physiological maximum pacing rate limit. The present subject matter provides a solution to problems associated with the use of a single maximum tracking rate (MTR). In one embodiment, the present subject matter utilizes two MTRs, where the first is a normal MTR and the second is a hysteresis MTR. In one embodiment, the hysteresis MTR is set higher than the normal MTR. The hysteresis MTR functions as a maximum pacing rate limit while tracking an atrial rate until the atrial rate exceeds the hysteresis MTR limit. When the atrial rate exceeds the hysteresis MTR limit, the maximum pacing rate limit is set to the normal MTR. Once the atrial rate falls below a predetermined threshold, the maximum pacing rate limit is set to the hysteresis MTR. The predetermined threshold may be set to the normal MTR, the hysteresis MTR, or other rates. In one embodiment, changing the maximum pacing rate limit in this fashion allows for uninterrupted pacing treatment for patients, such as congestive heart failure (CHF) patients, who may display fast but physiologically normal heart rates and need cardiac resynchronization therapy (CRT) at such fast heart rates. Such a pacing treatment provides for a more rapid and natural maximum pacing rate limit for the patient, while still protecting the patient from being paced at abnormally high rates.

Claims

1. A method, including:

sensing a first cardiac signal from a ventricular location;

detecting ventricular depolarizations from the first cardiac signal;

determining a heart rate based on the ventricular depolarizations;

comparing the heart rate to a first predetermined value and a second predetermined value, the second value larger than the first value;

setting a maximum ventricular pacing rate to the first predetermined value when the heart rate exceeds the second predetermined value; and

setting the maximum ventricular pacing rate to the second predetermined value when the heart rate falls below a predetermined threshold.

2. The method of claim 1, wherein the maximum ventricular pacing rate is a maximum tracking rate (MTR).

3. The method of claim 1, wherein the predetermined threshold is set to the first predetermined value.

4. The method of claim 1, wherein the predetermined threshold is set to the second predetermined value.

5. The method of claim 1, wherein setting the maximum ventricular pacing rate to the first predetermined value when the heart rate exceeds the second predetermined value includes changing the maximum ventricular pacing rate from the second predetermined value to the first predetermined value over a predetermined time interval.

6. The method of claim 1, further including:

sensing a second cardiac signal from an atrial location;

detecting atrial depolarizations from the second cardiac signal;

setting the PVARP to a first set value when the maximum ventricular pacing rate is set to the first predetermined value; and

setting the PVARP to a second set value when the maximum ventricular pacing rate is set to the second predetermined value.

7. The method of claim 6, further including:

calculating the first predetermined value based on at least the first set value and an atrioventricular pacing delay (AV delay); and

calculating the second predetermined value based on at least the second set value and the AV delay.

8. The method of claim 6, further including:

calculating the first predetermined value based on at least the first set value, an AV delay, and a first sensing window interval; and

calculating the second predetermined value based on at least the second set value, the AV delay, and a second sensing window interval.

9. The method of claim 8, wherein:

the first sensing window interval is a predetermined percentage of a sum of the first set value and the AV delay; and

the second sensing window interval is a predetermined percentage of a sum of the second set value and the AV delay.

10. The method of claim 8, wherein the sensing window interval is a programmable value being a function of at least one of the first and second predetermined values.

11. The method of claim 6, further including extending the PVARP associated with the first predetermined value for at least one cardiac cycle length after setting the maximum ventricular pacing rate to the first predetermined value when the heart rate exceeds the second predetermined value.

12. The method of claim 6, further including calculating the second predetermined value from the PVARP and an AV delay.

13. The method of claim 1, further including:

sensing a second cardiac signal from an atrial location;

detecting atrial depolarizations from the second cardiac signal; and

ignoring any atrial depolarization and not triggering an AV delay for one cardiac cycle every N cardiac cycles when the heart rate exceeds the first predetermined value.

14. The method of claim 1, further including:

sensing a second cardiac signal from an atrial location;

detecting atrial depolarizations from the second cardiac signal; and

setting the maximum ventricular pacing rate to the first predetermined value when an atrial depolarization is sensed during a postventricular atrial refractory period (PVARP).

15. The method of claim 1, further including:

sensing a second cardiac signal from an atrial location;

detecting atrial depolarizations from the second cardiac signal; and

setting the maximum ventricular pacing rate to the first predetermined value when at least a predetermined number of atrial depolarizations are sensed during postventricular atrial refractory periods (PVARPS) over a predetermined number of consecutive cardiac cycles.

16. The method of claim 1, further including:

delivering ventricular pacing pulses; and

setting the maximum ventricular pacing rate to the first predetermined value when the ventricular pacing pulses are delivered at a rate equal to the second predetermined value.

17. A cardiac rhythm management system, including:

a first lead adapted to sense a first cardiac signal in or about a ventricle of a heart;

a first sensing circuit, coupled to the first lead, including;

a first sense amplifier, coupled to the first lead, to receive the first cardiac signal; and

a first cardiac depolarization detector, coupled to the first sense amplifier, to detect ventricular depolarizations in the first cardiac signal;

a controller, coupled to the first sensing circuit, including;

a rate detector, coupled to the first cardiac depolarization detector, to

determine a heart rate from detected ventricular depolarizations,

a comparator, coupled to the rate detector, including inputs representative of the heart rate and at least one of a first predetermined value, a second predetermined value, and a predetermined threshold and one or more outputs representative of whether the heart rate exceeds the second predetermined value and whether heart rate falls below the predetermined threshold;

a storage medium, coupled to the comparator, including the first predetermined value, the second predetermined value, and the predetermined threshold; and

a pacing algorithm module, coupled to the comparator, to set a maximum ventricular pacing rate to the first predetermined value when the heart rate exceeds the second predetermined value, and set the maximum ventricular pacing rate to the second predetermined value when the heart rate falls below a predetermined threshold.

18. The cardiac rhythm management system of claim 17, wherein the maximum ventricular pacing rate is a maximum tracking rate (MTR).

19. The cardiac rhythm management system of claim 17, wherein the predetermined threshold is equal to the first predetermined value.

20. The cardiac rhythm management system of claim 17, wherein the predetermined threshold is equal to the second predetermined value.

21. The cardiac rhythm management system of claim 17, further including:

a second lead adapted to sense a second cardiac signal in or about an atrium of a heart; and

a second sensing circuit, coupled to the second lead, including;

a second sense amplifier, coupled to the second lead, to receive the second cardiac signal; and

a second cardiac depolarization detector, coupled to the second sense amplifier, to detect atrial depolarizations in the second cardiac signal.

22. The cardiac rhythm management system of claim 21, further including a therapy circuit, coupled to the controller, to deliver pacing pulses to the heart via at least one of the first and second leads.