Cardiac rhythm management system with arrhythmia prediction and prevention

• US 20010020136A1
• Filed: 05/07/2001
• Published: 09/06/2001
• Est. Priority Date: 10/01/1999
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Sweeney, Robert J., KenKnight, Bruce H.
• Granted Patent: US 6,400,982 B2
• Time in Patent Office: Days
• 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:

estimated arrhythmia probability=CP×

(1−

e<sup>−

CT</sup>).

11. The method of

claim 1

wherein the conditional arrhythmia probability is calculated by the expression:

1−

e<sup>−

RT</sup>

where T is a measure of the specified prediction time period, and R is an estimate of the rate at which arrhythmias occur while the conditioning event is present.

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:

estimated arrhythmia probability=CP×

(1−

e<sup>−

CT</sup>).

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 1

further comprising delivering a preventive arrhythmia therapy if the estimated arrhythmia probability exceeds a exceeds a therapy threshold.

34. The method of

claim 33

further comprising selecting a particular therapy to be delivered from a group of one or more available therapy modalities.

35. The method of

claim 34

wherein the group of available therapy modalities includes delivery of one or more of a plurality of pharmacological agents.

36. The method of

claim 34

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.

37. The method of

claim 34

wherein the group of available therapy modalities includes issuance of a warning signal.

38. The method of

claim 34

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.

39. The method of

claim 38

wherein the physiologic state ascertained for selecting a therapy modality includes the prediction time period of the estimated arrhythmia probability.

40. The method of

claim 38

wherein the physiologic state ascertained for selecting a therapy mode includes the particular conditioning events used to make the arrhythmia prediction.

41. The method of

claim 38

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.

42. The method of

claim 38

wherein the physiologic state ascertained for selecting a therapy mode includes the magnitude of a measured physiologic variable.

43. The method of

claim 38

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.

44. The method of

claim 19

wherein a separate estimated arrhythmia probability is computed for each of a plurality of types of arrhythmias.

45. A processor-readable storage medium having processor-executable instructions for performing the method recited in

claim 1

.

46. A processor-readable storage medium having processor-executable instructions for performing the method recited in

claim 19

.

47. A processor-readable storage medium having processor-executable instructions for performing the method recited in

claim 33

.

48. A cardiac rhythm management system, including:

a sensing module for detecting conditioning events statistically associated with occurrences of arrhythmias; and

,

an arrhythmia prediction module for 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 occur s alone or together with an arrhythmia within a specified time period.

49. The system of

claim 48

wherein the sensing module detects conditioning events selected from a group consisting of a specific morphology of a waveform representing electrical activity of the heart, a specific pattern of activation times of different areas of the heart as sensed by a plurality of electrodes, a specific sequence pattern of heartbeats with respect to time, a value of a measured physiological variable, and a statistic based upon a history of occurrences of conditioning events.

50. The system of

claim 48

wherein the sensing module detects a plurality of conditioning events statistically associated with the occurrence of an arrhythmia and further wherein the arrhythmia prediction module compares a composite estimated arrhythmia probability 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.

51. The system of

claim 50

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

52. The system of

claim 50

further comprising an adaptive processing module for computing conditional arrhythmia probabilities based upon past observations of the occurrences of events and arrhythmias taken in real-time from a particular patient.

53. The system of

claim 52

wherein the conditional arrhythmia probabilities computed by the adaptive processing module 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.

54. The system of

claim 53

wherein the adaptive processing module tests the amount by which the present value differs from the previous value for statistical significance before updating a conditional arrhythmia probability.

55. The system of

claim 52

wherein the adaptive processing module tests the statistical association of a conditional arrhythmia probability with real-time observation data and discontinues use of a conditional arrhythmia probability in deriving a composite conditional probability if the statistical association is below a specified value.

56. The system of

claim 48

further comprising a therapy module for delivering a preventive arrhythmia therapy if the estimated arrhythmia probability exceeds a therapy threshold.

57. The system of

claim 56

further comprising a preventive therapy control module for selecting a particular therapy to be delivered from a group of one or more available therapy modalities.

58. The system of

claim 57

wherein the group of available therapy modalities includes at least one of:

delivery of one or more of a plurality of pharmacological agents, cardiac pacing in a selected pacing mode, delivery of cardioversion/defibrillation shocks, and neural stimulation.

59. The system of

claim 57

wherein the selection of a particular therapy to be delivered by the therapy control module 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.

60. The system of

claim 59

wherein the physiologic state ascertained for selecting a therapy modality by the therapy control module includes at least one of:

the prediction time period of the estimated arrhythmia probability, the particular conditioning events used to make the arrhythmia prediction, the presence or not of specific conditioning events within a specified prior time period, and the magnitude of a measured physiologic variable.

61. The system of

claim 60

wherein the therapy control module decides whether or not to deliver a particular mode of preventive therapy by performing a matrix mapping of a list of detected conditioning events 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 detected conditioning event, and further wherein the mapping results in a score for each therapy modality represented in the matrix that is indicative of the appropriateness of each such therapy modality given the list of detected conditioning events, the score being evaluated by the therapy control module.

62. The system of

claim 60

wherein the therapy control module decides whether or not to deliver a particular mode of preventive therapy by performing 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 therapy matrix containing information relating to the appropriateness of a particular therapy modality for a given physiologic state.