Apparatus and method for treating ventricular tachyarrhythmias

• US 6,317,632 B1
• Filed: 10/11/2000
• Issued: 11/13/2001
• Est. Priority Date: 04/30/1997
• Status: Expired due to Term

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Zimmer, William L., Dreher, Robert D., Wald, Jan D., Gilkerson, James O., Linder, William J., Krig, David B.
• Primary Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US09/686,585
• Time in Patent Office: 398 Days
• Field of Search: 607/4, 607/5, 607/9, 607/14
• US Class Current: 607/14
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions
• CPC Class Codes: A61N 1/395 for treating atrial fibrillation
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

A system and method for selectively treating a ventricular tachycardia based on sensed atrial and ventricular intervals from the patient'"'"'s heart. A detection window of the ten most recent atrial and ventricular intervals are analyzed for the occurrence of either tachycardia or fibrillation. When a majority of the sensed intervals are satisfied, the apparatus starts a duration time interval. Ventricular intervals and atrial intervals are compare, ventricular interval greater than the atrial interval by a bias factor the system delivers tachycardia therapy to the heart. Alternatively, the method withholds tachycardia therapy to the heart when the atrial rate is classified as atrial fibrillation and the ventricular response is unstable.

Claims

1. An implantable cardioverter-defibrillator, comprising:

an atrial catheter having at least one atrial sensing/pacing electrode;

a ventricular catheter having at least one ventricular sensing/pacing electrode and at least one ventricular defibrillation electrode;

electronic control circuitry connected to the atrial catheter and the ventricular catheter, wherein the electronic control circuitry includes a microcontroller, memory, sensing electronics, and therapy delivery electronics to apply or inhibit ventricular tachycardia therapy;

wherein the sensing electronics are adapted to sense atrial events and ventricular events from the electrodes;

wherein the memory is adapted to store a lower rate threshold value for each of two or more rate zones, a ventricular tachycardia therapy for each of the two or more rate zones, a first predetermined percentage and a bias factor;

wherein the microcontroller is adapted to calculate an average atrial rate from the sensed atrial events, to calculate an average ventricular rate from sensed ventricular events, and to calculate ventricular interval rates from pairs of consecutively sensed ventricular events in a detection window, wherein the detection window is a predetermined series of ventricular events, and wherein the microcontroller is further adapted to compare each of the ventricular interval rates in the detection window to the lower rate threshold value for each of two or more rate zones, and to classify a ventricular interval rate of the ventricular interval rates as a fast ventricular interval for a rate zone of the two or more rate zones when the ventricular interval rate is equal to or greater than the lower rate threshold value of the rate zone, the microcontroller further adapted to declare the detection window satisfied when the first predetermined percentage of the ventricular interval rates in the detection window are classified as fast ventricular intervals for the rate zone, and to start a duration time interval once the detection window is declared satisfied, and wherein the microcontroller is adapted to control the therapy delivery electronics to inhibit ventricular tachycardia therapy during a sustained duration time period, wherein the sustained duration time period is started at the expiration of the duration time interval, and wherein the microcontroller is adapted to control the therapy delivery electronics to apply the previously inhibited ventricular tachycardia therapy for the rate zone when the average ventricular rate becomes greater than the average atrial rate by at least the bias factor during the sustained duration time period.

2. The implantable cardioverter-defibrillator of claim 1, wherein the microcontroller is adapted to determine whether the ventricular rate is unstable during the sustained duration time period, and controls the therapy delivery electronics to inhibit ventricular tachycardiac therapy when the ventricular rate is unstable for the sustained duration time period.

3. The implantable cardioverter-defibrillator of claim 2, wherein the microcontroller is adapted to determine whether the ventricular rate is stable during the sustained duration time period, to determine the occurrence of atrial fibrillation from the sensed atrial events, and to control the therapy delivery electronics to inhibit ventricular tachycardiac therapy when the ventricular rate is unstable and atrial fibrillation is occurring.

4. The implantable cardioverter-defibrillator of claim 3, wherein the microcontroller is adapted to determine whether the ventricular rate becomes stable during the sustained duration time period, and to control the therapy delivery electronics to apply the ventricular tachycardia therapy for the rate zone when there is atrial fibrillation and the ventricular rate becomes stable during the sustained duration time period.

5. The implantable cardioverter-defibrillator of claim 3, wherein the microcontroller determines the occurrence of atrial fibrillation from the sensed atrial events after the duration time interval ends when more than a predetermined majority number of a set of sensed atrial intervals is shorter than an atrial fibrillation interval threshold value, and when more than a predetermined quorum number of subsequent sets of sensed atrial intervals remain shorter than the atrial fibrillation interval threshold value.

6. The implantable cardioverter-defibrillator of claim 1, wherein the microcontroller controls the therapy delivery electronics to apply ventricular tachycardia therapy for the rate zone after the sustained duration time period ends.

7. The implantable cardioverter-defibrillator of claim 1, wherein the microcontroller controls the therapy delivery electronics to apply ventricular tachycardia therapy for the rate zone when the average ventricular rate is greater than the average atrial rate by at least the bias factor during the duration time interval.

8. The implantable cardioverter-defibrillator of claim 1, wherein the memory is adapted to store an onset rate value, and the microcontroller determines an onset rate for the ventricular rate and when the onset rate of the ventricular rate is below a previously programmed onset rate value the microcontroller controls the therapy delivery electronics to inhibit the ventricular tachycardia therapy for the sustained duration time period.

9. The implantable cardioverter-defibrillator of claim 1, wherein the microcontroller declares the detection window remains satisfied when a second predetermined percentage of the ventricular interval rates following the detection window are classified as fast ventricular intervals for the rate zone, and wherein the microcontroller is adapted to reset the duration time interval to zero when the detection window fails to remain satisfied during the duration time interval.

10. An apparatus comprising:

electronic control circuitry, adapted to be connected to atrial and ventricular electrodes, wherein the electronic control circuitry includes a microcontroller, memory, sensing electronics, and therapy delivery electronics to apply or inhibit ventricular tachycardia therapy;

wherein the sensing electronics are adapted to sense atrial and ventricular events from the electrodes;

wherein the memory is adapted to store;

lower rate threshold values defining corresponding rate zones;

ventricular tachycardia therapies corresponding to the rate zones;

a first predetermined percentage; and

a bias factor; and

wherein the microcontroller;

is adapted to calculate average atrial and ventricular rates from respective sensed atrial and ventricular events;

includes a detection window defined by a predetermined series of ventricular events;

is adapted to calculate a ventricular interval rate from consecutive ventricular events in the detection window, and to compare the ventricular interval rate in the detection window to one or more lower rate threshold values for the rate zones, and to classify the ventricular interval rate as fast when the ventricular interval rate greater than or equal to the lower rate threshold value;

is adapted to control the therapy delivery electronics to inhibit ventricular tachycardia therapy for a first time interval after the first predetermined percentage of the ventricular interval rates in the detection window are classified as fast;

is adapted to control the therapy delivery electronics to apply the previously inhibited ventricular tachycardia therapy corresponding to the rate zone when the average ventricular rate exceeds the average atrial rate by at least the bias factor during the first time interval.

11. The apparatus of claim 10, wherein the microcontroller is adapted to determine whether the ventricular rate is unstable during the first time interval, and controls the therapy delivery electronics to inhibit ventricular tachycardiac therapy when the ventricular rate is unstable.

12. The apparatus of claim 11, wherein the microcontroller is adapted to determine whether the ventricular rate is stable during the first time interval, to determine the occurrence of atrial fibrillation from the sensed atrial events, and to control the therapy delivery electronics to inhibit ventricular tachycardiac therapy when the ventricular rate is unstable and atrial fibrillation is occurring.

13. The apparatus of claim 12, wherein the microcontroller is adapted to determine whether the ventricular rate becomes stable during the first time interval, and to control the therapy delivery electronics to apply the ventricular tachycardia therapy corresponding to the rate zone when there is atrial fibrillation and the ventricular rate becomes stable during the first time period.

14. The apparatus of claim 12, wherein the microcontroller determines the occurrence of atrial fibrillation from the sensed atrial events when more than a predetermined majority of the sensed atrial intervals are shorter than a threshold value, and when more than a predetermined number of subsequent sensed atrial intervals remain shorter than the threshold value.

15. The apparatus claim 10, wherein the microcontroller controls the therapy delivery electronics to apply ventricular tachycardia therapy corresponding to the rate zone after the first time period ends.

16. The apparatus of claim 10, wherein the microcontroller controls the therapy delivery electronics to apply ventricular tachycardia therapy corresponding to the rate zone when the average ventricular rate exceeds the average atrial rate by at least the bias factor during a second time interval initiated after the first predetermined percentage of the ventricular interval rates in the detection window are classified as fast.

17. The apparatus of claim 10, wherein the memory includes an onset rate value, and the microcontroller determines an present onset rate for the ventricular rate, and when the present onset rate is below a previously programmed onset rate value, the microcontroller controls the therapy delivery electronics to inhibit the ventricular tachycardia therapy for the first time period.