METHOD AND DEVICES FOR PERFORMING CARDIAC WAVEFORM APPRAISAL

• US 20080015647A1
• Filed: 07/23/2007
• Published: 01/17/2008
• Est. Priority Date: 06/02/2003
• Status: Active Grant

• Current Assignee: Cameron Incorporated (Schlumberger NV)
• Original Assignee: Cameron Incorporated (Schlumberger NV)
• Inventors: Warren, Jay, Phillips, James, Palreddy, Surekha
• Granted Patent: US 7,996,082 B2
• Time in Patent Office: Days
• US Class Current: 607/5
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/287 Holders for multiple electrodes, e.g. electrode catheters for electrophysiological study [EPS]
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions
• CPC Class Codes: A61N 1/365 controlled by a physiological parameter, e.g. heart potential evoked response A61N1/371
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence

Abstract

Implementations of various technologies described herein are directed toward a sensing architecture for use in cardiac rhythm management devices. The sensing architecture may provide a method and means for certifying detected events by the cardiac rhythm management device. Moreover, by exploiting the enhanced capability to accurately identifying only those sensed events that are desirable, and preventing the use of events marked as suspect, the sensing architecture can better discriminate between rhythms appropriate for device therapy and those that are not.

Claims

1. A method of monitoring cardiac function in an implanted cardiac rhythm device comprising:

monitoring a signal produced between implanted electrodes to observe an event;

observing an event and gathering a signal corresponding to the event;

observing characteristic features of the slope of the signal;

counting the characteristic features;

comparing the number of characteristic features to a threshold to;

certify the signal for use in characterizing a cardiac complex;

or

determine the signal is unsuitable for use in characterizing a cardiac complex; and

if the signal is certified, using the signal to determine whether a malignant cardiac rhythm is likely occurring.

2. The method of claim 1 wherein:

the step of counting the characteristics features includes identifying an integer value equal to how many characteristic features there are in the signal; and

the step of comparing the number of characteristic features to a threshold includes comparing the integer value to the threshold.

3. The method of claim 2 wherein the step of comparing the characteristic features to the threshold is performed as a single comparison of an integer value to the threshold for each observed event.

4. The method of claim 1, wherein the step of observing characteristic features includes identifying a number of points in the signal where the signal slope reaches a local maximum magnitude.

5. The method of claim 4, wherein the step of observing characteristic features includes:

selecting a first zero crossing as a significant maximum slope point; and

characterizing subsequent zero crossings as either significant maximum slope points or not significant maximum slope points;

wherein the significant maximum slope points are observed to be the characteristic features.

6. The method of claim 5, wherein the step of characterizing subsequent zero crossings includes application of a rule related to a threshold for consideration of separate points in the signal.

7. The method of claim 6, wherein the rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds a path length threshold.

8. The method of claim 7, wherein the path length threshold is related to a selected percentage of the maximum signal amplitude for a chosen cardiac complex.

9. The method of claim 5, wherein the step of characterizing subsequent zero crossings includes application of a rule related to the signal shape between two points in the signal.

10. The method of claim 9, wherein the rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds the magnitude of the difference in amplitude between:

the signal at the time of the most recent significant maximum slope point; and

the signal at the time of the zero crossing under consideration.

11. The method of claim 5, wherein the step of characterizing subsequent zero crossings includes analysis using a first rule and a second rule, the first rule being related to a threshold for consideration of separate points in the signal, the second rule being related to the signal shape between two points in the signal.

12. The method of claim 11, wherein:

the first rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds a path length threshold; and

the second rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds the magnitude of the difference in amplitude between;

the signal at the time of the most recent significant maximum slope point; and

the signal at the time of the zero crossing under consideration.

13. The method of claim 1, wherein:

the step of observing characteristic features of the signal includes;

sampling the signal to generate a set samples; and

dividing the sampled signal into divisions each including a plurality of the samples;

the step of counting the characteristics features includes counting how many of the divisions are monotonic to yield a number M; and

the step of comparing the number of characteristic features to the threshold includes comparing M to the threshold.

14. A method of cardiac rhythm management using an implanted cardiac rhythm management device, the method comprising:

capturing a signal using implanted electrodes placed for observing electrical cardiac activity;

analyzing the signal to determine whether the signal is suitable for characterizing a cardiac rhythm;

if the signal is suitable, using the signal to determine whether a malignant cardiac rhythm is likely occurring; and

if the signal is not suitable, rejecting the signal.

15. The method of claim 14 wherein the step of analyzing the signal to determine whether the signal is suitable for characterizing a cardiac rhythm includes:

dividing the captured signal into a number of samples, and dividing the number of samples into a number of time-contiguous divisions;

counting how many of the number of divisions are monotonic to yield a number, M; and

comparing M to a threshold;

wherein if M is greater than the threshold, the signal is found to be suitable.

16. The method of claim 14 wherein the step of analyzing the signal to determine whether the signal is suitable for characterizing a cardiac rhythm includes:

observing how many characteristic features there are in the signal to yield a number, M; and

comparing M to a threshold;

wherein if M is less than the threshold, the signal is found to be suitable.

17. The method of claim 16 wherein the characteristic features are local maxima in the signal.

18. The method of claim 16 wherein the characteristic features are local maxima in the signal which pass a test related to the path length between consecutive characteristic features.

19. The method of claim 18 wherein the test comprises first and second rules, and:

the first rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds a path length threshold; and

the second rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds the magnitude of the difference in amplitude between;

the signal at the time of the most recent significant maximum slope point; and

the signal at the time of the zero crossing under consideration.

20. An implantable cardioverter/defibrillator (ICD) comprising:

a lead electrode assembly including a number of electrodes; and

a canister housing operational circuitry;

wherein;

the lead electrode assembly is coupled to the canister; and

the operational circuitry is configured to;

monitor a signal produced between implanted electrodes to observe an event;

observe an event and gathering a signal corresponding to the event;

observe characteristic features of the shape of the signal;

count the characteristic features;

compare the number of characteristic features to a threshold to;

certify the signal for use in characterizing a cardiac complex;

or

determine the signal is unsuitable for use in characterizing a cardiac complex;

and, if the signal is certified, use the signal to determine whether a malignant cardiac rhythm is likely occurring.

21. The ICD of claim 20 wherein the operational circuitry is configured such that:

the step of counting the characteristics features includes identifying an integer value equal to how many characteristic features there are in the signal; and

the step of comparing the number of characteristic features to a threshold includes comparing the integer value to the threshold.

22. The method of claim 21 wherein the operational circuitry is configured such that the step of comparing the characteristic features to the threshold is performed as a single comparison of an integer value to the threshold for each observed event.

23. The ICD of claim 20 wherein the operational circuitry is configured such that the step of observing characteristic features includes identifying a number of points in the signal where the signal slope reaches a local maximum magnitude.

24. The ICD of claim 23 wherein the operational circuitry is configured such that the step of observing characteristic features includes:

selecting a first zero crossing as a significant maximum slope point; and

characterizing subsequent zero crossings as either significant maximum slope points or not significant maximum slope points;

wherein the significant maximum slope points are observed to be the characteristic features.

25. The ICD of claim 24 wherein the operational circuitry is configured such that the step of characterizing subsequent zero crossings includes application of a rule related to a threshold for consideration of separate points in the signal.

26. The ICD of claim 25 wherein the operational circuitry is configured such that the rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds a path length threshold.

27. The ICD of claim 26 wherein the operational circuitry is configured such that the path length threshold is related to a selected percentage of the maximum signal amplitude for a chosen cardiac complex.

28. The ICD of claim 24 wherein the operational circuitry is configured such that the step of characterizing subsequent zero crossings includes application of a rule related to the signal shape between two points in the signal.

29. The ICD of claim 28 wherein the operational circuitry is configured such that the rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds the magnitude of the difference in amplitude between:

the signal at the time of the most recent significant maximum slope point; and

the signal at the time of the zero crossing under consideration.

30. The ICD of claim 24 wherein the operational circuitry is configured such that the step of characterizing subsequent zero crossings includes analysis using a first rule and a second rule, the first rule being related to a threshold for consideration of separate points in the signal, the second rule being related to the signal shape between two points in the signal.

31. The ICD of claim 30 wherein the operational circuitry is configured such that:

the first rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds a path length threshold; and

the second rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds the magnitude of the difference in amplitude between;

the signal at the time of the most recent significant maximum slope point; and

the signal at the time of the zero crossing under consideration.

32. The ICD of claim 20 wherein the operational circuitry is configured such that:

the step of observing characteristic features of the signal includes;

sampling the signal to generate a set samples; and

dividing the sampled signal into divisions each including a plurality of the samples;

the step of counting the characteristics features includes counting how many of the divisions are monotonic to yield a number M; and

the step of comparing the number of characteristic features to the threshold includes comparing M to the threshold.

33. An implantable cardioverter/defibrillator (ICD) comprising:

a lead electrode assembly including a number of electrodes; and

a canister housing operational circuitry;

wherein;

the lead electrode assembly is coupled to the canister; and

the operational circuitry is configured to;

capture a signal using implanted electrodes placed for observing electrical cardiac activity;

analyze the signal to determine whether the signal is suitable for characterizing a cardiac rhythm; and

if the signal is suitable, use the signal to determine whether a malignant cardiac rhythm is likely occurring;

if the signal is not suitable, reject the signal.

34. The ICD of claim 33 wherein the operational circuitry is configured such that the step of analyzing the signal to determine whether the signal is suitable for characterizing a cardiac rhythm includes:

dividing the captured signal into a number of samples, and dividing the number of samples into a number of time-contiguous divisions;

counting how many of the number of divisions are monotonic to yield a number, M; and

comparing M to a threshold;

wherein if M is greater than the threshold, the signal is found to be suitable.

35. The ICD of claim 33 wherein the operational circuitry is configured such that the step of analyzing the signal to determine whether the signal is suitable for characterizing a cardiac rhythm includes:

observing how many characteristic features there are in the signal to yield a number, M; and

comparing M to a threshold;

wherein if M is less than the threshold, the signal is found to be suitable.

36. The ICD of claim 35 wherein the operational circuitry is configured such that the characteristic features are local maxima in the signal.

37. The ICD of claim 35 wherein the operational circuitry is configured such that the characteristic features are local maxima in the signal which pass a test related to the path length between consecutive characteristic features.

38. The ICD of claim 37 wherein the operational circuitry is configured such that the test comprises first and second rules, and:

the first rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds a path length threshold; and

the second rule calls for determining whether the path length from a most recent significant maximum slope point to the zero crossing under consideration exceeds the magnitude of the difference in amplitude between;

the signal at the time of the most recent significant maximum slope point; and

the signal at the time of the zero crossing under consideration.