Automated template generation algorithm for implantable device

• US 20020087091A1
• Filed: 11/26/2001
• Published: 07/04/2002
• Est. Priority Date: 11/28/2000
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Gillberg, Jeffrey M., Koyrakh, Lev A., Davydov, Eugene
• Granted Patent: US 6,745,068 B2
• Time in Patent Office: Days
• US Class Current: 600/521
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

A method of generating a template in an implantable medical device for implantation within a patient, and a processor readable medium for performing the method, that includes generating a template corresponding to a supraventricular rhythm of the patient, determining whether the template is valid, and monitoring the template to determine whether the template is an accurate representation of the supraventricular rhythm. The template is created from non-paced R waves that are below a predetermined heart rate, and a statistical validation of the template is performed by evaluating the template based on matches against ongoing slow heart rhythm. The quality of the template is continuously monitored, similar to the statistical validation, with the exception that one thousand beats are evaluated and once more than thirty out of the last one hundred beats do not match the template within the threshold, an attempt is made to create a new template.

Claims

1. A method of generating a template in an implantable medical device for implantation within a patient, comprising the steps of:

generating a template corresponding to a supraventricular rhythm of the patient;

determining whether the template is valid; and

monitoring the template to determine whether the template is an accurate representation of the supraventricular rhythm.

2. The method of claim 1, further comprising the steps of:

generating a new template in response to the template not being an accurate representation; and

continuing to monitor the template in response to the template being an accurate representation.

3. The method of claim 1, wherein the step of generating a template comprises the steps of:

monitoring a heart rate of the patient;

determining whether beats corresponding to the heart rate are one of a paced beat and less than a predetermined rate;

determining whether a predetermined number of beats have been collected and computing cross matches between the predetermined number of collected beats to form corresponding computed cross matches;

determining whether a predetermined number of the computed cross matches exceed a threshold; and

forming the template from the predetermined number of computed cross matches in response to the predetermined number of the computed cross matches exceeding the threshold.

4. The method of claim 1, wherein the step of generating a template comprises the steps of:

monitoring a heart rate of the patient;

determining whether beats corresponding to the heart rate are one of a paced beat and less than a predetermined rate;

determining whether an RR interval corresponding to the beats is within a predetermined threshold of an average RR interval;

determining whether a predetermined number of beats have been collected and computing cross matches between the predetermined number of collected beats to form corresponding computed cross matches;

determining whether a predetermined number of the computed cross matches exceed a threshold; and

forming the template from the predetermined number of computed cross matches in response to the predetermined number of the computed cross matches exceeding the threshold.

5. The method of claim 3, further comprising the steps of:

determining whether a predetermined time period has been exceeded in response to beats corresponding to the heart rate being one of a paced beat and less than the predetermined rate; and

aborting the template generation in response to the predetermined time period being exceeded.

6. The method of claim 3, further comprising the steps of:

determining whether a predetermined time period has been exceeded in response to the predetermined number of computed cross matches not exceeding the predetermined threshold; and

aborting the template generation in response to the predetermined time period being exceeded.

7. The method of claim 3, wherein the predetermined number of beats is six and the predetermined number of computed cross matches is four.

8. The method of claim 1, wherein the step of determining whether the template is valid comprises the steps of:

computing a match between subsequently collected beats and the template;

determining whether the match is within a predetermined threshold to form matched beats and other than matched beats;

determining whether the other than matched beats is greater than a first number of beats; and

determining the template is valid in response to the matched beats being greater than or equal to a second number of beats.

9. The method of claim 8, wherein the step of computing a match comprises computing the match for one out of every one hundred subsequently collected beats and the template.

10. The method of claim 8, wherein the step of determining whether the template is valid further comprises the step of repeating the step of generating a template in response to the other than matched beats being greater than the first number of beats.

11. The method of claim 8, wherein the first number of beats is thirty and the second number of beats is seventy.

12. The method of claim 8, further comprising, in response to the matched beats not being greater than or equal to the second number of beats, the steps of:

determining whether a match has been computed for a predetermined number of beats;

determining whether a time period has been exceeded in response to the match not being computed for the predetermined number of beats; and

aborting the template generation in response to the predetermined time period being exceeded.

13. The method of claim 12, wherein the first number of beats is thirty, the second number of beats is seventy, and the predetermined number of beats is one hundred.

14. The method of claim 1, wherein the step of monitoring the template comprises the steps of:

(a) computing a match between a subsequently collected beat and the template;

(b) determining whether the match is within a predetermined threshold to form matched beats and other than matched beats;

(c) determining whether x out of the last y subsequently collected beats are other than matched beats; and

(d) repeating steps (a)-(c) in response to x out of the last y beats not being other than matched beats.

15. The method of claim 14, wherein the step of computing a match comprises computing the match for one out of every one thousand subsequently collected beats and the template

16. The method of claim 14, further comprising the step of repeating the step of generating a template in response to x out of the last y beats being other than matched beats.

17. The method of claim 14, wherein x is thirty and y is one hundred.

19. The processor readable medium of claim 18, wherein the generating means generates a new template in response to the template not being an accurate representation;

and continues to monitor the template in response to the template being an accurate representation

20. The processor readable medium of claim 18, wherein the generating means monitors a heart rate of the patient, determines whether beats corresponding to the heart rate are one of a paced beat and less than a predetermined rate, determines whether a predetermined number of beats have been collected and computes cross matches between the predetermined number of collected beats to form corresponding computed cross matches, determines whether a predetermined number of the computed cross matches exceeds a threshold, and forms the template from the predetermined number of computed cross matches in response to the predetermined number of the computed cross matches exceeding the threshold.

21. The processor readable medium of claim 18, wherein the generating means monitors a heart rate of the patient, determines whether beats corresponding to the heart rate are one of a paced beat and less than a predetermined rate, determines whether an RR interval corresponding to the beats is within a predetermined threshold of an average RR interval, determines whether a predetermined number of beats have been collected and computes cross matches between the predetermined number of collected beats to form corresponding computed cross matches, determines whether a predetermined number of the computed cross matches exceeds a threshold, and forms the template from the predetermined number of computed cross matches in response to the predetermined number of the computed cross matches exceeding the threshold.

22. The processor readable medium of claim 18, wherein the generating means determines whether a predetermined time period has been exceeded in response to beats corresponding to the heart rate being one of a paced beat and less than a predetermined rate, and aborts the template generation in response to the predetermined time period being exceeded.

23. The processor readable medium of claim 19, wherein the generating means determines whether a predetermined time period has been exceeded in response to the predetermined number of computed cross matches not exceeding the predetermined threshold, and aborts the template generation in response to the predetermined time period being exceeded.

24. The processor readable medium of claim 18, wherein the generating means computes a match between subsequently collected beats and the template, determines whether the match is within a predetermined threshold to form matched beats and other than matched beats, and determines the validity of the template based on the number of matched beats and the number of other than matched beats.

25. The processor readable medium of claim 24, wherein the generating means determines whether a match has been computed for a predetermined number of beats, determines whether a time period has been exceeded in response to the match not being computed for the predetermined number of beats, and aborts the template generation in response to the predetermined time period being exceeded.

26. The processor readable medium of claim 18, wherein the generating means (a) computes a match between subsequently collected beats and the template, (b) determines whether the match is within a predetermined threshold to form matched beats and other than matched beats, (c) determines whether x out of the last y subsequently collected beats are other than matched beats, and (d) repeats (a)-(c) in response to x out of the last y subsequently collected beats not being other than matched beats.

27. The processor readable medium of claim 26, wherein the generating means computes the match for one out of every one thousand subsequently collected beats and the template.

28. The processor readable medium of claim 26, wherein the x is thirty and y is one hundred.

29. The processor readable medium of claim 20, wherein the generating means re-generates the template in response to x out of the last y beats being other than matched beats.

18. A processor readable medium in an implantable medical device, comprising:

means for sensing an R wave; and

means for generating a template corresponding to a supraventricular rhythm of the patient based on the sensed R wave, the means for generating a template further determining whether the template is valid and monitoring the template to determine whether the template is an accurate representation of the supraventricular rhythm.

30. A method of generating a template in an implantable medical device for implantation within a patient, comprising the steps of:

(a) monitoring a heart rate of the patient;

(b) determining whether beats corresponding to the heart rate are one of a paced beat and less than a predetermined rate;

(c) determining whether a predetermined number of beats have been collected and computing cross matches between the predetermined number of collected beats to form corresponding computed cross matches;

(d) determining whether a predetermined number of the computed cross matches exceeds a first predetermined threshold;

(e) forming the template from the predetermined number of computed cross matches in response to the predetermined number of the computed cross matches exceeding the first predetermined threshold;

(f) computing a first match between subsequently collected beats and the template to form first matches;

(g) determining whether the first match is within a second predetermined threshold to form first matched beats and first other than matched beats;

(h) determining whether the first other than matched beats is greater than a first number of beats;

(i) determining the template is valid in response to the matched beats being equal to a second number of beats;

(j) computing a second match between a next subsequently collected beat and the template to form a second match;

(k) determining whether the second match is within a third predetermined threshold to form second matched beats and second other than matched beats;

(l) determining whether x out of the last y next subsequently collected beats are other than matched beats; and

(m) repeating steps (j)-(l) in response to x out of the last y next subsequently collected beats not being other than matched beats.

31. The method of claim 30, further comprising the steps of repeating steps (a)-(e) in response to the first other than matched beats being greater than the first number of beats and in response to x out of the last y next subsequently collected beats being other than matched beats.

32. The method of claim 31, wherein the step of computing a first match comprises computing the first match for one out of every one hundred of the subsequently collected beats and the step of computing a second match comprises computing the second match for one out of every one thousand of the next subsequently collected beats.

33. The method of claim 32, further comprising the steps of:

(n) determining whether a first time period has been exceeded in response to determining, in step (d), that the predetermined number of computed cross matches does not exceed the first predetermined threshold;

(o) aborting the template generation in response to the predetermined time period being exceeded;

(p) determining a total number of the first matches;

(q) determining whether a second time period has been exceeded in response to the total number of first matches being less than a predetermined number of first matches; and

(v) aborting the template generation in response to the second time period being exceeded.

34. The method of claim 33, further comprising, in response to beats corresponding to the heart rate are not one of a paced beat and less than a predetermined rate, the step of determining whether an RR interval corresponding to the beats is within a predetermined threshold of an average RR interval.

36. The method of claim 35 further comprising the step of determining whether an RR interval corresponding to the beats is within a predetermined threshold of an average RR interval.

35. A method of generating a template from beats corresponding to a supraventricular rhythm of a patient in an implantable medical device, comprising the steps of:

(a) determining whether six beats have been collected and computing cross matches between the six collected beats to form corresponding computed cross matches;

(b) determining whether four of the computed cross matches exceeds a first predetermined threshold;

(c) forming the template from the four computed cross matches in response to the four computed cross matches exceeding the first predetermined threshold;

(d) determining whether a first time limit has been exceeded and repeating steps (a)-(c) in response to the four computed cross matches not exceeding the first predetermined threshold;

(e) computing a first match between one out of a hundred subsequently collected beats and the template to form first matches;

(f) determining whether the first match is within a second predetermined threshold to form first matched beats and second unmatched beats;

(g) repeating steps (a)-(f) in response to thirty out of the last one hundred subsequently collected beats being first unmatched beats;

(h) determining the template is valid in response to seventy out of the last one hundred subsequently collected beats being first matched beats;

(i) determining whether a second time limit has been exceeded and repeating steps (e)-(h) in response to seventy out of the last one hundred subsequently collected beats not being first matched beats;

(j) computing a second match between one out of one thousand next subsequently collected beats and the template to form a second match;

(k) determining whether the second match is within a third predetermined threshold to form second matched beats and second unmatched beats;

(l) repeating steps (j)-(k) in response to thirty out of the last one hundred next subsequently collected beats not being unmatched beats; and

(m) repeating steps (a)-(l) in response to thirty out of the last one hundred next subsequently collected beats being unmatched beats.