Method and apparatus for discrimination atrial fibrillation using ventricular rate detection

• US 20020065473A1
• Filed: 11/28/2001
• Published: 05/30/2002
• Est. Priority Date: 11/28/2000
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Wang, Li, Brown, Mark L.
• Granted Patent: US 6,922,584 B2
• Time in Patent Office: Days
• US Class Current: 600/518
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/7232 involving compression of the physiological signal, e.g. to extend the signal recording period

Abstract

A method and apparatus for method for discriminating heart rhythms includes computing a first predetermined number of RR intervals from received QRS intervals, and computing a median RR interval corresponding to a predetermined number of the first predetermined number of RR intervals. A predetermined beat-to-beat variation and a corresponding predetermined count are determined based on the computed median RR interval. Beat-to-beat variation differences between the first predetermined number of RR intervals are computed and a determination is made as to whether the computed beat-to-beat variation differences are greater than the predetermined beat-to-beat variation, and as to whether a number of the computed beat-to-beat variation differences that are greater than the predetermined beat-to-beat variation is greater than the predetermined count. The heart rhythm is identified as an irregular rhythm in response to the number being greater than or equal to the predetermined count.

Claims

1. An implantable medical device, comprising:

sensing means for sensing cardiac activity of a patient;

first detector means for differentiating arrhythmias in response to differences in ventricular rate variabilities in the sensed cardiac activity and outputting a signal in response to the differentiated arrhythmias; and

trigger means for receiving the signal from the detector means and initiating storage of the sensed cardiac activity.

2. The device of claim 1, wherein the first detector means determines a number of beat-to-beat variations that are greater than a predetermined beat-to-beat variation and identifies the cardiac activity in response to the number.

3. The device of claim 2, wherein the first detector means determines whether the number of beat-to-beat variations that are greater than a predetermined beat-to-beat variation is greater than or equal to a predetermined count associated with the predetermined beat-to-beat variation.

4. The device of claim 2, wherein the cardiac activity is determined to be an irregular rhythm in response to the number of beat-to-beat variations that are greater than the predetermined beat-to-beat variation being greater than or equal to a predetermined count associated with the predetermined beat-to-beat variation.

5. The device of claim 2, wherein the cardiac activity is determined to be a regular rhythm in response to the number of beat-to-beat variations that are greater than the predetermined beat-to-beat variation being less than a predetermined count associated with the predetermined beat-to-beat variation.

6. The device of claim 1, further comprising second detector means for detecting a QRS interval corresponding to the cardiac activity to compute a first predetermined number of RR intervals, and wherein the first detector means computes a median RR interval corresponding to a predetermined number of the first predetermined number of RR intervals, computes beat-to-beat variation differences between the first predetermined number of RR intervals, and compares the beat-to-beat variation differences to a predetermined beat-to-beat variation corresponding to the median RR interval.

7. The device of claim 6, wherein the beat-to-beat variation differences are calculated by taking the difference of the absolute value of RR(n)-RR(n−

1), wherein RR(n) and RR(n−

1) are consecutive RR intervals of the first predetermined number of RR intervals.

8. The device of claim 6, wherein the first detector means determines whether a number of the beat-to-beat variation differences that are greater than the predetermined beat-to-beat variation is greater than a predetermined count associated with the predetermined beat-to-beat variation.

9. The device of claim 8, wherein the cardiac activity is determined to be associated with an irregular rhythm in response to the number of the beat-to-beat variation differences that are greater than the predetermined beat-to-beat variation being greater than the predetermined count.

10. The device of claim 9, wherein the irregular rhythm corresponds to atrial fibrillation.

11. A method for discriminating heart rhythms in an implantable medical device, comprising the steps of:

receiving a QRS interval corresponding to the heart rhythm and computing a first predetermined number of RR intervals from the received QRS intervals;

computing a median RR interval corresponding to a predetermined number of the first predetermined number of RR intervals;

determining a predetermined beat-to-beat variation corresponding to the computed median RR interval;

computing beat-to-beat variation differences between the first predetermined number of RR intervals;

comparing the beat-to-beat variation differences to the predetermined beat-to-beat variation to determine variations in the beat-to-beat variation differences; and

identifying the heart rhythm in response to the variations in the beat-to-beat variation differences.

12. The method of claim 11, wherein the step of computing beat-to-beat variation differences comprises calculating the difference of the absolute value of RR(n)-RR(n−

1), wherein RR(n) and RR(n−

1) are consecutive RR intervals of the first predetermined number of RR intervals.

13. The method of claim 11, wherein the step of comparing comprises the steps of:

determining the number of the beat-to-beat variation differences that are greater than the predetermined beat-to-beat variation; and

determining whether the number is greater than a predetermined count corresponding to the computed median RR interval.

14. The method of claim 13, wherein the step of identifying comprises the steps of:

identifying the heart rhythm as an irregular rhythm in response to the number being greater than or equal to the predetermined count; and

identifying the heart rhythm as a regular rhythm in response to the number being less than the predetermined count.

15. The method of claim 14, wherein the irregular rhythm corresponds to atrial fibrillation.

17. The method of claim 16, wherein the step of differentiating comprises the steps of:

determining a number of beat-to-beat variation differences that are greater than a predetermined beat-to-beat variation; and

identifying the cardiac activity in response to the number.

18. The method of claim 16, wherein the step of differentiating comprises the steps of:

detecting a QRS interval corresponding to the cardiac activity to compute a first predetermined number of RR interval;

computing a median RR interval corresponding to a predetermined number of the first predetermined number of RR intervals;

computing beat-to-beat variation differences between the first predetermined number of RR intervals; and

comparing the beat-to-beat variation differences to a predetermined beat-to-beat variation corresponding to the median RR interval.

19. The method of claim 18, wherein the beat-to-beat variation differences are calculated by taking the difference of the absolute value of RR(n)-RR(n−

1), wherein RR(n) and RR(n−

1) are consecutive RR intervals of the first predetermined number of RR intervals.

20. The method of claim 17, wherein the step of differentiating further comprises the step of determining whether the number of beat-to-beat variation differences that are greater than the predetermined beat-to-beat variation is greater than or equal to a predetermined count associated with the predetermined beat-to-beat variation.

21. The method of claim 17, wherein the step of identifying comprises the steps of:

determining the cardiac activity to be an irregular rhythm in response to the number of beat-to-beat variation differences that are greater than the predetermined beat-to-beat variation being greater than or equal to a predetermined count associated with the predetermined beat-to-beat variation; and

determining the cardiac activity to be a regular rhythm in response to the number of beat-to-beat variation differences that are greater than the predetermined beat-to-beat variation being less than the predetermined count.

22. The method of claim 21, wherein the irregular rhythm corresponds to atrial fibrillation.

24. The method of claim 23, wherein the beat-to-beat variation differences are computed by taking the difference of the absolute value of RR(n)-RR(n−

1), wherein RR(n) and RR(n−

1) are consecutive RR intervals of the first predetermined number of RR intervals, and wherein the irregular rhythm corresponds to atrial fibrillation.

16. A method for discriminating heart rhythms in an implantable medical device, comprising the steps of:

sensing cardiac activity of a patient;

differentiating arrhythmias corresponding to differences in ventricular rate variabilities in the sensed cardiac activity; and

storing the sensed cardiac activity in response to the differentiated arrhythmias.

23. A method for discriminating between heart rhythms in an implantable medical device, comprising the steps of:

computing a first predetermined number of RR intervals from received QRS intervals;

computing a median RR interval corresponding to a predetermined number of the first predetermined number of RR intervals;

determining a predetermined beat-to-beat variation and a corresponding predetermined count associated with the computed median RR interval;

computing beat-to-beat variation differences between the first predetermined number of RR intervals;

determining whether the computed beat-to-beat variation differences are greater than the predetermined beat-to-beat variation; and

determining whether a number of the computed beat-to-beat variation differences that are greater than the predetermined beat-to-beat variation is greater than the predetermined count;

identifying the heart rhythm as an irregular rhythm in response to the number being greater than or equal to the predetermined count; and

identifying the heart rhythm as a regular rhythm in response to the number being less than the predetermined count.