Implantable stimulation device and method for discrimination atrial and ventricular arrhythmias

• US 6,671,548 B1
• Filed: 08/30/2000
• Issued: 12/30/2003
• Est. Priority Date: 12/29/1999
• Status: Expired due to Fees

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Inventors: Mouchawar, Gabriel A., Badelt, Steven W., Street, Anne M.
• Primary Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US09/651,287
• Time in Patent Office: 1,217 Days
• Field of Search: 607/4, 607/5, 607/14, 607/25, 607/9, 600/515, 600/516, 600/518
• US Class Current: 607/14
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions

Abstract

By redistributing the running totals for various preliminary classifications to other preliminary classifications based upon the values of the most recent cardiac events, the present invention biases the running totals (thereby biasing the duration criteria) to help overcome common discrimination problems which permits the stimulation device to make a correct and final therapy decision more quickly. To identify a patient'"'"'s heart rhythm, various electrical events such as P-waves and R-waves, and their timing, relationship, and stability, are detected and a preliminary classification is made for each detected event. Running totals of the numbers of all events detected within each of the preliminary classifications are maintained, along with sliding totals covering only the most recently detected events. Then, the arrhythmia is identified based upon an analysis of both the running totals and the sliding totals. In a preferred embodiment, the arrhythmia is identified by first determining whether the sliding total of the number of detected events in any one of the preliminary classifications exceeds a corresponding sliding total threshold. If so, the running totals are then selectively redistributed based upon the sliding totals. The final decision is then made based upon whether the running total corresponding to any one of the preliminary classifications exceeds a corresponding running total threshold. Both method and apparatus embodiments are disclosed. Methods are further described for determining the preliminary classifications of the detected events.

Claims

1. In an implantable stimulation device, a method for discriminating various arrhythmias of a patient'"'"'s heart, the method comprising the steps of:

detecting cardiac events within the heart beginning at an initial point in time;

determining a preliminary classification for each cardiac event for a plurality of heart rhythms to establish predetermined classifications;

maintaining running totals of the number of cardiac events within each of the predetermined classifications since the initial point in time;

maintaining sliding totals of the number of cardiac events within each of the predetermined classifications out of a group of most recent cardiac events;

determining whether the sliding total in any one of the predetermined classifications exceeds a corresponding predetermined sliding total threshold and, if so, selectively redistributing the running totals of the predetermined classifications since the initial point in time; and

determining whether the redistributed running total in any one of the predetermined classifications exceeds a corresponding predetermined running total threshold and, if so, identifying the patient'"'"'s heart rhythm as being the heart rhythm corresponding to the predetermined classification in which the predetermined running total threshold was exceeded.

2. The method of claim 1, wherein the preliminary classifications for the plurality of heart rhythms include normal sinus rhythm (NSR), ventricular fibrillation (VF), ventricular tachycardia without 1:

1 retrograde conduction (VT not 1;

1), ventricular tachycardia with 1;

1 retrograde conduction (VT 1;

1), atrial fibrillation (AF) and sinus tachycardia (ST).

3. The method of claim 2, wherein the step of selectively redistributing the running totals comprises the step of:

clearing the running totals of all of the predetermined classifications whenever the sliding total for the preliminary classification of normal sinus rhythm (NSR) exceeds the corresponding predetermined sliding total threshold.

4. The method of claim 2, wherein the step of selectively redistributing the running totals comprises the steps of:

adding the running totals for ST, VT 1;

1 and VT not 1;

1 to the running total for VF and then clearing the running totals for ST, VT 1;

1, VT not 1;

1 and AF, whenever the sliding total having a preliminary classification of VF exceeds the corresponding predetermined sliding total threshold.

5. The method of claim 4, the step of selectively redistributing the running totals comprises the steps of:

tracking the amount of time elapsed following an R-R interval which has a corresponding ventricular rate that exceeds a predetermined rate threshold indicative of a tachyarrhythmia; and

adding the running totals for ST, VT 1;

1 and VT not 1;

1 to the running total for VF, and then clearing the running totals for ST, VT 1;

1, VT not 1;

1 and AF, whenever the amount of elapsed time exceeds a predetermined threshold.

6. The method of claim 2, wherein the step of selectively redistributing the running totals comprises the steps of:

adding the running totals for ST and VT 1;

1 to the running total for VT not 1;

1, and then clearing the running totals for ST, VT 1;

1, and AF, whenever the sliding total having a preliminary classification of VT not 1;

1 exceeds the corresponding predetermined sliding total threshold.

7. The method of claim 2, wherein the step of selectively redistributing the running totals comprises the steps of:

adding the running totals for ST, VT not 1;

1 and VF to the running total for VT 1;

1, and then clearing the running totals for ST, VT not 1;

1, VF and AF, whenever the sliding total having a preliminary classification of VT 1;

1 exceeds the corresponding predetermined sliding total threshold.

8. The method of claim 2, wherein the step of selectively redistributing the running totals comprises the steps of:

adding the running totals for VT not 1;

1 and VF to the running total for VT 1;

1, and then clearing the running totals for VT not 1;

1, VF and AF, whenever the sliding total having a preliminary classification of ST exceeds the corresponding predetermined sliding total threshold.

9. The method of claim 2, wherein the step of selectively redistributing the running totals comprises the step of:

clearing the running totals for ST, VT 1;

1, and VT not 1;

1, whenever the sliding total having a preliminary classification of AF exceeds the corresponding predetermined sliding total threshold.

10. The method of claim 1, wherein the step of determining a preliminary classification for each detected cardiac event comprises the steps of:

determining that the heart rate is greater than a low tachycardia rate zone; and

assigning a preliminary classification of VF when the cardiac event is greater than the tachycardia rate zone.

11. The method of claim 1, wherein the step of determining a preliminary classification for each detected cardiac event comprises the steps of:

determining that the heart rate is within a low tachycardia rate zone; and

determining that a 1;

1 P-R association does exist.

12. The method of claim 11, wherein the step of determining a preliminary classification for each detected cardiac event further comprises the steps of:

determining whether the cardiac event is a premature ventricular complex (PVC); and

assigning a preliminary classification of VT not 1;

1 when the cardiac event is determined to be a PVC.

13. The method of claim 11, wherein the step of determining a preliminary classification for each detected cardiac event further comprises the steps of:

determining if the P-R interval is between predetermined maximum and minimum thresholds; and

assigning a preliminary classification of VT 1;

1 when the P-R interval is not between the predetermined maximum and minimum thresholds.

14. The method of claim 11, wherein the means for determining a preliminary classification for each detected cardiac event further comprises the steps of:

determining whether the P-R intervals are stable;

assigning a preliminary classification of VT 1;

1 when the P-R interval is not stable and is between the predetermined maximum and minimum thresholds; and

assigning a preliminary classification of ST when the P-R interval is stable and is between the predetermined maximum and minimum thresholds.

15. The method of claim 1, wherein the step of determining a preliminary classification for each cardiac event further comprises the steps of:

determining that the heart rate is within a tachycardia rate zone; and

determining that a 1;

1 P-R association does not exist.

16. The method of claim 15, wherein the step of determining a preliminary classification for each cardiac event further comprises the steps of:

determining that the atrial rate does not exceed the ventricular rate; and

assigning a preliminary classification of VT not 1;

1.

17. The method of claim 15, wherein the step of determining a preliminary classification for each cardiac event further comprises the steps of:

determining that the atrial rate does exceed the ventricular rate;

determining if the R-R interval is stable; and

assigning a preliminary classification of AF when the R-R is not stable.

18. The method of claim 17, wherein the step of determining a preliminary classification for each cardiac event further comprises the steps of:

determining whether the R-P intervals are stable;

assigning a preliminary classification of AF when the R-R intervals are stable and the R-P interval is stable; and

assigning a preliminary classification of VT not 1;

1 when the R-R intervals are stable and the R-P interval is not stable.

19. An implantable stimulation device having means for discriminating various arrhythmias of a patient'"'"'s heart and for applying therapy in response thereto, comprising:

a sensing circuit that senses cardiac events;

a memory coupled to the sensing circuit to store a sequence of cardiac events, the memory including a circular buffer for storing a predetermined number of cardiac events that occurred most recently within the sequence;

a control circuit coupled to the sensing circuit to determine a preliminary classification for each sensed cardiac event to establish predetermined classifications;

a first counter coupled to the memory to count a running total for each of the cardiac events within each of the predetermined classifications based on all cardiac events sensed from an initial point in time;

a second counter coupled to the memory to count a sliding total for each of the cardiac events within each of the predetermined classifications based on the cardiac events contained within the circular buffer;

the control circuit further comprising;

a first detector that detects when the sliding total of any one of the predetermined classifications exceeds a corresponding sliding total threshold;

means, coupled to the first detector, for redistributing the running totals of the predetermined classifications since the initial point in time whenever one of the sliding total exceeds its corresponding sliding total threshold;

a second detector that detects when the redistributed running total of any one of the predetermined classifications exceeds a corresponding running total threshold; and

means, coupled to the second detector, for identifying the patient'"'"'s heart rhythm as being the rhythm corresponding to the predetermined classification which exceeds a corresponding running total threshold.

20. The device of claim 19, wherein the predetermined classifications includes at least normal sinus rhythm (NSR), ventricular fibrillation (VF), ventricular tachycardia without 1:

1 retrograde conduction (VT not 1;

1), ventricular tachycardia with 1;

1 retrograde conduction (VT 1;

1), atrial fibrillation (AF), and sinus tachycardia (ST).

21. The device of claim 20, wherein the control circuit further comprises:

timing means for determining a plurality of timing characteristics of atrial and ventricular rhythms, including determining a ventricular rate corresponding to an R-R interval, an atrial rate corresponding to a P-P interval, an R-P interval, and a P-R interval;

means, coupled to the timing means, for determining if a 1;

1 P-R association exists, and

means for determining the preliminary classification of VF, VT not 1;

1, or VT 1;

1 based on the ventricular rate and the presence of absence of a 1;

1 P-R association.

22. The device of claim 21, wherein:

the timing means further includes means for determining a presence of a premature ventricular complex (PVC), an indicator that the R-R interval is stable, an indicator that the R-P interval is stable, an indicator that a P-R interval is physiologic, an Indicator that a P-R interval is stable, and an indicator when the ventricular rate is either above, or within, a high rate zone; and

means, coupled to the timing means, for determining a preliminary classification of VT not 1;

1, VT 1;

1, ST, or AF based on the plurality of ventricular and atrial timing characteristics.

23. The device of claim 22, wherein the control circuit determines a preliminary classification of VT not 1:

1 whenever one of the following is detected;

a 1;

1 P-R association exists but was due to a PVC;

a 1;

1 P-R association does not exist and the ventricular rate exceeds the atrial rate; and

a 1;

1 P-R association does not exist and the atrial rate exceeds the ventricular rate together with a stable R-R interval and an unstable R-P interval.

24. The device of claim 22, wherein the control circuit determines a preliminary classification of ST whenever the following is detected:

a 1;

1 P-R association does exists together with a physiological P-R interval and a stable P-R interval.

25. The device of claim 24, further comprising:

means for detecting a physiological need for a high atrial heart rate;

means for identifying the event as a pathological SVT 1;

1 when a physiological need does not exist; and

identifying the event as a physiological ST when physiological need does exist.

26. The device of claim 25, wherein the means for detecting a physiological need for a high atrial heart rate comprises:

a physiologic sensor that detects when the patient is in an exercise state thereby indicating a physiological need for a high heart rate.

27. The device of claim 25, wherein the means for detecting a physiological need for a high atrial heart rate comprises:

means for detecting slow and sudden onset of the heart rhythm, wherein a high heart rate is needed only when a slow onset occurs.

28. The device of claim 22, wherein the control circuit determines a preliminary classification of AF whenever the detection of a 1:

1 P-R association does not occur, the atrial rate is detected to exceed the ventricular rate, and one of a non-stable R-R interval is detected or a stable R-R interval is detected concurrent with a stable R-P interval.

29. The device of claim 22, wherein the control circuit determines a preliminary classification of VT 1:

1 whenever one of a 1;

1 P-R association exists and the P-R interval is not physiologic, or a 1;

1 P-R association exists, the P-R interval is physiologic, and the P-R interval is not stable.