Methods and devices for determination of arrhythmia rate zone thresholds

• US 20080045851A1
• Filed: 08/18/2006
• Published: 02/21/2008
• Est. Priority Date: 08/18/2006
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Kim, Jaeho, Ricci, Carlos Alberto, Cazares, Shelley Marie
• Granted Patent: US 7,580,741 B2
• Time in Patent Office: Days
• US Class Current: 600/515
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

Approaches for determining threshold values for one or more arrhythmia rate zones and/or the number of rate zones are described. A probability function for heart rate is determined using collected and measured heart rate values. One or more heart rate probability values are selected. Thresholds for arrhythmia rate zones are determined from the probability function based on the selected probability values. Determining the rate zone thresholds may involve determining a threshold for a lower rate limit and/or determining one or more tachyarrhythmia rate zone thresholds. The number of rate zones may also be determined based on the probability function.

Claims

1. A method for detecting cardiac arrhythmia;

comprising;

collecting measured heart rate values;

determining a probability function for heart rate using the collected and measured heart rate values;

selecting one or more heart rate probability values; and

determining one or more rate zone thresholds for arrhythmia rate zones from the probability function based on the one or more probability values.

2. The method of claim 1, further comprising detecting cardiac tachyarrhythmia based on the rate zone thresholds.

3. The method of claim 1, wherein:

the collected and measured heart rate values comprise RR intervals;

determining the probability function comprises determining the probability function using the RR intervals; and

determining the one or more rate zone thresholds comprises determining one or more ventricular rate thresholds.

4. The method of claim 1, wherein:

the collected and measured heart rate values comprise PP intervals;

determining the probability function comprises determining the probability function using the PP intervals; and

determining the one or more rate zone thresholds comprises determining one or more atrial rate thresholds.

5. The method of claim 1, wherein the probability function comprises a cumulative density function.

6. The method of claim 1, wherein selecting the one or more probability values comprises entering one or more fractional probability values via a patient-external device.

7. The method of claim 1, wherein determining the one or more rate thresholds comprises using the probability function as a lookup table and the one or more probability values as indexes to the lookup table.

8. The method of claim 1, wherein determining the one or more rate thresholds comprises solving the probability function by inputting the one or more probability values into the equation to determine the one or more rate thresholds.

9. The method of claim 1, wherein determining the one or more rate zone thresholds comprises determining a threshold for a lower rate limit.

10. The method of claim 1, wherein determining the one or more rate zone thresholds comprises determining one or more tachyarrhythmia rate zone thresholds.

11. The method of claim 1, further comprising determining a number of the arrhythmia rate zones based on the probability function.

12. The method of claim 1, wherein the probability function comprises a one dimensional probability function of ventricular rate values.

13. The method of claim 1, wherein the probability function comprises a one dimensional probability function of atrial rate values.

14. The method of claim 1, wherein the probability function comprises a two dimensional probability function of atrial rate values and ventricular rate values.

15. The method of claim 14, comprising:

identifying atrioventricular patterns based on the two dimensional probability function of atrial rate values and ventricular rate values; and

determining the one or more rate zone thresholds comprises determining the rate zone thresholds based on the two dimensional probability function.

16. The method of claim 1, wherein determining the one or more rate zone thresholds comprises determining multiple rate thresholds respectively associated with multiple rate zones.

17. The method of claim 16, further comprising:

detecting arrhythmia based on the multiple rate zones; and

delivering cardiac stimulation therapy to treat the arrhythmia.

18. The method of claim 17, wherein delivering the cardiac stimulation therapy comprises delivering multiple therapies, each therapy respectively associated with one of the multiple rate zones.

19. A cardiac device, comprising:

sensing circuitry configured to sense cardiac electrical signals;

heart rate measurement circuitry coupled to the sensing circuitry and configured to measure heart rate values based on the sensed cardiac electrical signals;

a memory buffer configured to store the measured heart rate values;

a rate zone processor configured to develop a probability function for heart rate based on the measured heart rate values and to determine at least one rate zone threshold from the probability function based a heart rate probability value.

20. The device of claim 19, wherein the rate zone processor is configured to automatically select the heart rate probability value.

21. The device of claim 19, further comprising communication circuitry configured to receive the heart rate probability value entered via a patient-external device.

22. The device of claim 19, wherein the rate zone processor is configured to use the probability function as a look up table to determine the rate zone threshold using the heart rate probability value as an index.

23. The device of claim 19, wherein the rate zone processor is configured to solve the probability function using the heart rate probability value to determine the rate zone threshold.

24. The device of claim 19, wherein:

the heart rate measurement circuitry is configured to measure intervals between cardiac beats; and

the rate zone processor is configured to develop the probability function based on the measured intervals.

25. The device of claim 19, wherein the probability function comprises a cumulative density function.

26. The device of claim 19, wherein the rate zone processor is further configured to determine a number of rate zones based on the probability function.

27. The device of claim 19, wherein the probability function comprises a multi-dimensional probability function of atrial and ventricular heart rate values.

28. The device of claim 19, further comprising:

detection circuitry configured to detect arrhythmia based on the rate zone threshold; and

therapy circuitry configured to deliver electrical stimulation therapy to treat the arrhythmia.

29. A method for detecting cardiac arrhythmia, comprising:

collecting measured heart rate values;

determining a probability function for the collected and measured heart rate values; and

determining a number of rate zones for tachyarrhythmia detection based on the probability function.

30. The method of claim 29, wherein determining the number of rate zones comprises:

detecting one or more features of the probability function; and

determining the number of rate zones based on a number of the one or more features.

31. The method of claim 29, wherein:

the probability function comprises a cumulative distribution function; and

determining the number of rate zones comprises analyzing the cumulative distribution function to identify flat portions of the cumulative distribution function.

32. The method of claim 29, wherein:

the probability function comprises a probability density function; and

determining the number of rate zones comprises analyzing the probability density function to identify peaks of the probability density function.

33. The method of claim 29, further comprising periodically updating the number of rate zones.

34. A cardiac device, comprising:

sensing circuitry configured to sense cardiac electrical signals;

heart rate measurement circuitry coupled to the sensing circuitry and configured to collect and measure heart rate values based on the sensed cardiac electrical signals; and

a rate zone processor configured to determine a number of rate zones for tachyarrhythmia detection based on a probability function for the collected and measured heart rate values.

35. The device of claim 34, wherein:

the probability function comprises a cumulative distribution function; and

the rate zone processor is configured to analyze the cumulative distribution function to identify flat portions of the cumulative distribution function and to determine the number of rate zones for tachyarrhythmia detection based on the identified flat portions of the cumulative distribution function.

36. The device of claim 34, wherein:

the probability function comprises a probability density function; and

the rate zone processor is configured to analyze the cumulative distribution function to identify peaks of the probability density function and to determine the number of rate zones for tachyarrhythmia detection based on the identified peaks of the probability density function.

37. The device of claim 34, further comprising a tachyarrhythmia detector configured to detect tachyarrhythmia based on the number of rate zones.

38. The device of claim 34, further comprising a therapy circuit configured to deliver multiple tachyarrhythmia therapies, each therapy associated with a particular rate zone.