Cardiac rhythm management system with arrhythmia prediction and prevention

• US 6,272,377 B1
• Filed: 10/01/1999
• Issued: 08/07/2001
• Est. Priority Date: 10/01/1999
• Status: Expired due to Term

• Current Assignee: Advanced Micro Devices, Inc., Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Sweeney, Robert J., KenKnight, Bruce H.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US09/411,345
• Time in Patent Office: 676 Days
• Field of Search: 600/513, 600/518
• US Class Current: 600/515
• CPC Class Codes: A61N 1/3622 comprising two or more electrodes co-operating with different heart regions
• CPC Class Codes: G16H 50/30 for calculating health indices; for individual health risk assessment
• CPC Class Codes: G16Z 99/00 Subject matter not provided for in other main groups of this subclass

Abstract

A cardiac rhythm management system predicts when an arrhythmia will occur and in one embodiment invokes a therapy to prevent or reduce the consequences of the arrhythmia. A cardiac arrhythmia trigger/marker is detected from a patient, and based on the trigger/marker, the system estimates a probability of a cardiac arrhythmia occurring during a predetermined future time interval. The system provides a list of triggers/markers, for which detection values are recurrently obtained at various predetermined time intervals. Based on detection values and conditional probabilities associated with the triggers/markers, a probability estimate of a future arrhythmia is computed. An arrhythmia prevention therapy is selected and activated based on the probability estimate of the future arrhythmia.

Claims

1. A method, comprising:

detecting a conditioning event statistically associated with the occurrence of an arrhythmia in a patient'"'"'s heart; and

,

predicting the occurrence of an arrhythmia within a specified prediction time period if an estimated arrhythmia probability exceeds a specified threshold value, wherein the estimated arrhythmia probability is computed from a conditional arrhythmia probability associated with the conditioning event that is derived from past observations of instances in which the conditioning event occurs alone or together with an arrhythmia within a specified time period.

2. The method of claim 1 wherein the conditioning event is a marker event corresponding to detection of a physiological state statistically associated with occurrence of cardiac arrythmias.

3. The method of claim 1 wherein the conditioning event is a trigger event that increases the risk of an arrhythmia occurring via a depolarization that serves as a source for the arrhythmia.

4. The method of claim 1 wherein the conditioning event is a specific morphology of a waveform representing electrical activity of the heart.

5. The method of claim 1 wherein the conditioning event is a specific pattern of activation times of different areas of the heart as sensed by a plurality of electrodes.

6. The method of claim 1 wherein the conditioning event is a specific sequence pattern of heartbeats with respect to time.

7. The method of claim 1 wherein the conditioning event is a value of a measured physiological variable.

8. The method of claim 1 wherein the conditioning event is a statistic based upon a history of occurrences of conditioning events.

9. The method of claim 1 wherein the conditional arrhythmia probability CP is a ratio of the number of observed instances in which the conditioning event is followed by an arrhythmia within a specified basic time period to the total number of observed instances of the conditioning event.

10. The method of claim 9 further comprising estimating a rate C at which the conditioning event occurs, and further wherein the estimated arrhythmia probability is calculated by the expression:

11. The method of claim 1 wherein the conditional arrhythmia probability is calculated by the expression:

12. The method of claim 11 wherein the rate R is a ratio of:

1) the number of instances in which the conditioning event is followed by an arrhythmia within a specified basic time period, to

     2) the length of the basic time period multiplied by the total number of basic time periods in which the conditioning event is observed.

13. The method of claim 12 further comprising estimating a rate C at which the conditioning event occurs, and further wherein the estimated arrhythmia probability is calculated by the expression:

 

(1−

e<sup>−

RT</sup>)(1−

e<sup>−

CT</sup>).

14. The method of claim 1 further comprising assigning a culpability to a conditioning event for causing an observed instance of an arrhythmia when a specified criterion is met, and further wherein the conditional arrhythmia probability CP is a ratio of the number of observed instances in which the conditioning event was deemed culpable for causing an arrhythmia, to the total number of observed occurrences of the conditioning event.

15. The method of claim 14 further comprising estimating a rate C at which the conditioning event occurs, and further wherein the estimated arrhythmia probability is calculated by the expression:

16. The method of claim 14 wherein the culpability criterion is the proximity in time between the conditioning event and the onset of an arrhythmia.

17. The method of claim 14 wherein the culpability criterion is the magnitude of the detected conditioning event prior to the onset of an arrhythmia.

18. The method of claim 14 wherein the culpability criterion is the frequency of occurrence of the conditioning event within a specific time period prior to the onset of an arrhythmia.

19. The method of claim 1 wherein a plurality of conditioning events statistically associated with the occurrence of an arrhythmia are detected and further wherein a composite estimated arrhythmia probability is compared with the threshold value in order to predict the occurrence of an arrhythmia, the composite arrhythmia probability being a combination of the estimated arrhythmia probabilities associated with each detected conditioning event.

20. The method of claim 19 wherein the composite arrhythmia probability is calculated by adding the estimated arrhythmia probabilities associated with each detected conditioning event.

21. The method of claim 20 wherein the estimated arrhythmia probabilities associated with each detected conditioning event are calculated by multiplying the conditional arrhythmia probability derived for a conditioning event by the number of detected occurrences of the event within a specified time period.

22. The method of claim 19 wherein each conditional arrhythmia probability is a ratio of the number of instances in which the conditioning event is observed to be followed by an arrhythmia within a specified basic time period to the total number of observed instances of the conditioning event.

23. The method of claim 22 wherein the conditional arrhythmia probabilities are derived using different basic time periods.

24. The method of claim 19 wherein the conditional arrhythmia probabilities are based upon past observations of the occurrences of events and arrhythmias taken from population data.

25. The method of claim 19 wherein the conditional arrhythmia probabilities are based upon past observations of the occurrences of events and arrhythmias taken in real-time from a particular patient.

26. The method of claim 25 wherein the conditional arrhythmia probabilities are based initially upon past observations of the occurrences of events and arrhythmias taken from population data and each probability is subsequently updated from a previous value to a present value with observations taken in real-time from a particular patient.

27. The method of claim 25 further comprising periodically updating a conditional arrhythmia probability from a previous value to a present value with observations taken in real-time from a particular patient.

28. The method of claim 27 wherein a conditional arrhythmia probability is updated only if the present value differs by a predetermined amount from the previous value.

29. The method of claim 28 further comprising testing the amount by which the present value differs from the previous value for statistical significance before a conditional arrhythmia probability is updated.

30. The method of claim 25 further comprising testing the statistical association of a conditional arrhythmia probability with real-time observation data.

31. The method of claim 30 further comprising discontinuing use of a conditional arrhythmia probability in deriving a composite conditional probability if the statistical association is below a specified value.

32. The method of claim 25 further comprising incrementing or decrementing a conditional arrhythmia probability by a specific amount after a prediction time period in accordance with whether the arrhythmia occurred or not, respectively.

33. The method of claim 19 wherein a separate estimated arrhythmia probability is computed for each of a plurality of types of arrhythmias.

34. The method of claim 1 further comprising delivering a preventive arrhythmia therapy if the estimated arrhythmia probability exceeds a exceeds a therapy threshold.

35. The method of claim 34 further comprising selecting a particular therapy to be delivered from a group of one or more available therapy modalities.

36. The method of claim 35 wherein the group of available therapy modalities includes delivery of one or more of a plurality of pharmacological agents.

37. The method of claim 35 wherein the group of available therapy modalities includes modalities selected from a group consisting of cardiac pacing in a selected pacing mode, delivery of cardioversion/defibrillation shocks, and neural stimulation.

38. The method of claim 35 wherein the group of available therapy modalities includes issuance of a warning signal.

39. The method of claim 35 wherein the selection of a particular therapy to be delivered is based upon ascertaining a physiologic state of the patient and deciding whether or not a particular available modality of therapy is appropriate for delivery to the patient in that physiologic state.

40. The method of claim 39 wherein the physiologic state ascertained for selecting a therapy modality includes the prediction time period of the estimated arrhythmia probability.

41. The method of claim 39 wherein the physiologic state ascertained for selecting a therapy mode includes the particular conditioning events used to make the arrhythmia prediction.

42. The method of claim 39 wherein the physiologic state ascertained for selecting a therapy mode includes the presence or not of specific conditioning events within a specified prior time period.

43. The method of claim 39 wherein the physiologic state ascertained for selecting a therapy mode includes the magnitude of a measured physiologic variable.

44. The method of claim 39 wherein the decision as to whether or not to deliver a particular mode of preventive therapy takes the form of a matrix mapping of a state vector representing a specific physiologic state to a specific therapy or therapies considered most appropriate for preventing an arrhythmia in that physiologic state, wherein the matrix mapping is performed using a translation matrix containing information relating to the appropriateness of a particular therapy modality for a given physiologic state.