SYSTEM AND METHOD FOR MONITORING OR TREATING NERVOUS SYSTEM DISORDERS

• US 20070238939A1
• Filed: 04/27/2007
• Published: 10/11/2007
• Est. Priority Date: 12/17/2004
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Giftakis, Jonathon, Graves, Nina
• Granted Patent: US 8,112,153 B2
• Time in Patent Office: Days
• US Class Current: 600/301
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/02 Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/08 Detecting, measuring or recording devices for evaluating the respiratory organs A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/1135 by monitoring thoracic expansion
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16
• CPC Class Codes: A61B 5/4094 Diagnosing or monitoring seizure diseases, e.g. epilepsy
• CPC Class Codes: A61N 1/36064 Epilepsy
• CPC Class Codes: A61N 1/36082 Cognitive or psychiatric applications, e.g. dementia or Alzheimer's disease
• CPC Class Codes: A61N 1/3611 Respiration control stimulating respiratory organs A61N1/3601
• CPC Class Codes: A61N 1/365 controlled by a physiological parameter, e.g. heart potential evoked response A61N1/371
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters
• CPC Class Codes: A61N 1/37288 Communication to several implantable medical devices within one patient
• CPC Class Codes: A61N 1/3962 in combination with another heart therapy
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

A method of comparing cardiac and neurological event detection signals to indicate whether the cardiac event detection signal may facilitate detection of neurological events. The method includes obtaining a signal indicating detected neurological events, obtaining a signal indicating detected cardiac events, analyzing the timing relationships between the detected neurological and cardiac events to identify matched events, and using the matched events to indicate whether the cardiac event detection signal facilitates detection of neurological events.

Claims

1. A method of comparing a cardiac event detection signal to a neurological event detection signal, the method comprising:

obtaining a neurological event detection signal, the neurological event detection signal indicating detected neurological events in a patient;

obtaining a cardiac event detection signal, the cardiac event detection signal indicating detected cardiac events in the patient;

analyzing timing relationships between detected neurological events and cardiac events;

identifying a matched event when one of the detected neurological events is temporally related to one of the detected cardiac events; and

indicating whether the cardiac event detection signal facilitates detection of neurological events based on matched events.

2. The method of claim 1 further comprising identifying a false positive event when one of the detected cardiac events is not temporally related to one of the detected neurological events, and indicating whether the cardiac event detection signal facilitates detection of neurological events based upon matched events and false positive events.

3. The method of claim 1 further comprising identifying a false negative event when one of the detected neurological events is not temporally related to one of the detected cardiac events, and indicating whether the cardiac event detection signal facilitates detection of neurological events based upon matched events and false negative events.

4. The method of claim 1 further comprising:

identifying a false positive event when one of the detected cardiac events is not temporally related to one of the detected neurological events,

identifying a false negative event when one of the detected neurological events is not temporally related to one of the detected cardiac events, and

indicating whether the cardiac event detection signal facilitates detection of neurological events based upon matched events, false positive events, and false negative events

5. The method of claim 1 wherein a detected neurological event and a detected cardiac event are temporally matched if an elapsed time between a reference point of the detected neurological event and a reference point of the detected cardiac event is less than a predetermined amount.

6. The method of claim 5 wherein the reference point of each of the detected events is a beginning time of the event.

7. The method of claim 5 wherein the reference point of each of the detected events is an ending time of the event.

8. The method of claim 5 wherein the reference point for a first of the detected events is a beginning time of the first event, and the reference point for a second of the detected events is a ending time of the second event.

9. The method of claim 5 wherein the reference point of each of the detected events is between a beginning time and an ending time for each of the detected events.

10. The method of claim 9 wherein the reference point of each of the detected events is a midpoint between a beginning time and an ending time for each of the detected events.

11. The method of claim 1 further comprising calculating a rate of concordance between the neurological and cardiac event detection signals, and indicating that the cardiac event detection signal facilitates detection of the neurological events when the rate of concordance exceeds a threshold.

12. The method of claim 11 wherein calculating the rate of concordance comprises dividing a number of matched events by a number of detected neurological events.

13. The method of claim 11 further comprising enabling the cardiac event detection signal to detect neurological events when the rate of concordance between the neurological and cardiac event detection signals exceeds the threshold.

14. The method of claim 13 wherein a therapy for treating neurological events is delivered to the patient in response to the detected cardiac events.

15. The method of claim 14 wherein the therapy comprises delivery of electrical stimulation to a brain of the patient.

16. The method of claim 14 wherein the therapy comprises delivery of a drug to the patient.

17. The method of claim 2 further comprising calculating a false positive rate, the false positive rate being equal to a number of false positive events divided by a number of detected neurological events.

18. The method of claim 17 further comprising enabling the cardiac event detection signal to detect neurological events when the false positive rate is below a predetermined level.

19. The method of claim 2 further comprising calculating a false positive rate, the false positive rate being equal to a number of false positive events per unit of time.

20. The method of claim 19 further comprising enabling the cardiac event detection signal to detect neurological events when the false positive rate is below a predetermined level.

21. The method of claim 1 further comprising, for each of the matched events, determining a latency of the detected cardiac event with respect to a detected neurological event.

22. The method of claim 21 wherein determining latency comprises calculating a representative value of a time by which the matched cardiac events precede the corresponding matched neurological events.

23. The method of claim 21 wherein determining latency comprises calculating how frequently the matched cardiac events precede the corresponding matched neurological events.

24. The method of claim 21 further comprising enabling the cardiac event detection signal to detect neurological events when the latency of the detected cardiac events meets a predetermined criterion.

25. The method of claim 1 further comprising calculating a false negative rate, the false negative rate being equal to a number of false negative events divided by a number of detected neurological events.

26. The method of claim 25 further comprising enabling the cardiac event detection signal to detect neurological events when the false negative rate is below a predetermined level.

27. The method of claim 1 further comprising:

calculating a rate of concordance between the neurological and cardiac event detection signals, the rate of concordance being equal to a number of matched events divided by a number of detected neurological events;

calculating a false positive rate, the false positive rate being equal to a number of false positive events divided by the number of detected neurological events;

calculating a false negative rate, the false negative rate being equal to a number of false negative events divided by the number of detected neurological events;

for each of the matched events, determining a latency of the detected cardiac event with respect to a detected neurological event; and

enabling the cardiac event detection signal to detect neurological events when a combination of the rate of concordance, false positive rate, false negative rate, and latency of the detected cardiac events meet predetermined criteria.

28. The method of claim 1 further comprising:

calculating a rate of concordance between the neurological and cardiac event detection signals, the rate of concordance being equal to a number of matched events divided by a number of detected neurological events;

calculating a false positive rate, the false positive rate being equal to a number of false positive events per unit of time;

calculating a false negative rate, the false negative rate being equal to a number of false negative events divided by the number of detected neurological events;

for each of the matched events, determining a latency of the detected cardiac event with respect to a detected neurological event; and

enabling the cardiac event detection signal to detect neurological events when a combination of the rate of concordance, false positive rate, false negative rate, and latency of the detected cardiac events meet predetermined criteria.

29. The method of claim 1 wherein the neurological event detection signal is generated by a seizure detection algorithm which uses an EEG signal as an input.

30. The method of claim 1 wherein the neurological event detection signal is determined by physician analysis of EEG signals.

31. The method of claim 1 wherein the neurological event detection signal is determined by input from the patient.

32. The method of claim 1 wherein the cardiac event detection signal is determined by a detection algorithm which uses an ECG signal from the patient as an input.

33. The method of claim 32 wherein a cardiac event is detected by the cardiac event detection algorithm when a heart rate determined from the ECG signal exceeds a threshold.

34. The method of claim 33 wherein the cardiac event begins when the heart rate rises above a first threshold, and terminates when the heart rate decreases below a second threshold.

35. The method of claim 32 wherein the cardiac event is detected by the cardiac event detection algorithm when a change in heart rate determined from the ECG signal exceeds a threshold.

36. The method of claim 35 wherein the change in heart rate occurs within a predetermined window of time.

37. The method of claim 32 wherein the cardiac event is detected when one or more premature ventricular contractions (PVCs) occurs within a predetermined window of time.

38. The method of claim 32 wherein the cardiac event is detected when an arrhythmia occurs.

39. The method of claim 32 wherein each detected cardiac event is categorized as one or more of two or more types of cardiac events.

40. The method of claim 39 wherein each detected cardiac event is categorized as one or more of the following types:

bradycardia, tachycardia, asystole, wandering pacemaker, multifocal atrial tachycardia, atrial fibrillation, sinus pause, premature atrial contractions (PAC), ST segment elevation, ST segment depression, T-wave inversion, QT interval prolongation, premature ventricular contractions (PVCs), AV-block (AVB) and bundle branch block (BBB).

41. The method of claim 39 wherein the step of identifying matched events is performed separately for each type of cardiac event.

42. The method of claim 41 wherein a given type of cardiac event is enabled for detecting neurological events based on the number of matched events for the given type of cardiac event.

43. The method of claim 41 wherein a given type of cardiac event is enabled for detecting neurological events based on a rate of concordance between the given type of cardiac event and the detected neurological events.

44. The method of claim 41 wherein the type of cardiac event is one of bradycardia, tachycardia, asystole, ST segment elevation, QT interval prolongation, premature ventricular contractions (PVCs), and atrial fibrillation.

45. The method of claim 32 wherein the cardiac event is detected when a measured heart rate variability falls outside of a defined range.

46. The method of claim 32 wherein the cardiac event is detected when a measured QT interval variability falls outside of a defined range.

47. The method of claim 32 wherein the cardiac event is detected when a rate-corrected QT interval (“

QTc”

) falls outside of a defined range.

48. The method of claim 32 wherein the cardiac event is detected when a sinus arrest episode is detected.

49. The method of claim 32 wherein the cardiac event is detected when a syncope episode is detected.

50. The method of claim 49 wherein the syncope episode comprises a sudden drop in heart rate.

51. The method of claim 1 wherein a minimum number of neurological events must be detected before indicating whether the cardiac event detection signal facilitates detection of neurological events.

52. The method of claim 1, where, for the cardiac detections classified as matched, further classifying the cardiac detections as either:

(a) overlapping, if

(i) the cardiac event has a beginning time that occurs before an end time of the matched neurological event, and

(ii) the cardiac event has a termination time that occurs after a start time of the matched neurological event;

or

(b) non-overlapping.

53. The method of claim 52 wherein, for cardiac detections classified as overlapping, further classifying the cardiac detections as Equal-Equal if

(i) the cardiac event has a beginning time that equals a start time of the matched neurological event, and

(ii) the cardiac event has a termination time that equals an end time of the matched neurological event.

54. The method of claim 52 wherein, for cardiac detections classified as overlapping, further classifying the cardiac detections as Out-In if

(i) the cardiac event has a beginning time that occurs before a start time of the matched neurological event, and

(ii) the cardiac event has a termination time that occurs after the start time of the matched neurological event, and

(iii) the cardiac event termination time occurs before an end time of the matched neurological event.

55. The method of claim 52 wherein, for cardiac detections classified as overlapping, further classifying the cardiac detections as Out-Out if

(i) the cardiac event has a beginning time that occurs before a start time of the matched neurological event, and

(ii) the cardiac event has a termination time that occurs after an end time of the matched neurological event.

56. The method of claim 52 wherein, for cardiac detections classified as overlapping, further classifying the cardiac detections as In-Out if

(i) the cardiac event has a beginning time that occurs after a start time of the matched neurological event, and

(ii) the cardiac event beginning time occurs before an end time of the matched neurological event, and

(iii) the cardiac event has a termination time that occurs after the end time of the matched neurological event.

57. The method of claim 52 wherein, for cardiac detections classified as overlapping, further classifying the cardiac detections as In-In if

(i) the cardiac event has a beginning time that occurs after a start time of the matched neurological event, and

(ii) the cardiac event beginning time occurs before an end time of the matched neurological event, and

(iii) the cardiac event has a termination time that occurs after the start time of the matched neurological event, and

(iv) the cardiac event termination time occurs before the end time of the matched neurological event.

58. The method of claim 52 wherein, for cardiac detections classified as non-overlapping, further classifying the cardiac detections as Out-Equal if

(i) the cardiac event has a beginning time that occurs before a start time of the matched neurological event, and

(ii) the cardiac event has a termination time that is equal to the start time of the matched neurological event.

59. The method of claim 52 wherein, for cardiac detections classified as non-overlapping, further classifying the cardiac detections as Equal-Out if

(i) the cardiac event has a beginning time that is equal to an end time of the matched neurological event, and

(ii) the cardiac event has a termination time that occurs after the end time of the matched neurological event.

60. The method of claim 52 wherein, for cardiac detections classified as non-overlapping, further classifying the cardiac detections as Out-Out After Detect if

(i) the cardiac event has a beginning time that occurs within a predetermined window of time after an end time of the matched neurological event.

61. The method of claim 52 wherein, for cardiac detections classified as non-overlapping, further classifying the cardiac detections as Out-Out Before Detect if

(i) the cardiac event has a termination time that occurs within a predetermined window of time before a start time of the matched neurological event.

62. The method of claim 52 wherein, for cardiac detections classified as non-overlapping, indicating that the cardiac event may be predictive of a neurological event if the cardiac event has a termination time that occurs within a predetermined window of time before a start time of the neurological event.

63. The method of claim 1 further comprising:

classifying each matched event into one of two or more categories based upon the timing relationship between the cardiac and neurological events;

assigning a weighting factor to each matched event based upon the category for each matched event;

calculating a rate of concordance between the neurological and cardiac event detection signals utilizing the weighting factors, wherein calculating the rate of concordance comprises dividing a weighted sum of matched events by a number of detected neurological events; and

indicating that the cardiac event detection signal facilitates detection of the neurological events when the rate of concordance exceeds a threshold.

64. The method of claim 63 wherein the weighting factor for matched events in which the cardiac event precedes the neurological event is greater than 1.

65. The method of claim 63 wherein the weighting factor for matched events in which the cardiac event follows the neurological event is less than 1.

66. An implantable medical device (IMD) for processing cardiac and neurological event detection signals, the device comprising:

a biocompatible housing adapted to be implanted in a patient;

a power source; and

a processor, the processor being adapted to

obtain a neurological event detection signal, the neurological event detection signal indicating detected neurological events in the patient;

obtaining a cardiac event detection signal, the cardiac event detection signal indicating detected cardiac events in the patient;

analyzing timing relationships between detected neurological events and cardiac events;

identifying a matched event when one of the detected neurological events is temporally related to one of the detected cardiac events, and

indicating whether the cardiac event detection signal facilitates detection of neurological events based on the matched events.

67. The IMD of claim 66 wherein a detected neurological event and a detected cardiac event are temporally matched if an elapsed time between a reference point of the detected neurological event and a reference point of the detected cardiac event is less than a predetermined amount.

68. The IMD of claim 66 further comprising calculating a rate of concordance between the neurological and cardiac event detection signals, and indicating that the cardiac event detection signal facilitates detection of the neurological events when the rate of concordance exceeds a threshold.

69. The IMD of claim 68 wherein calculating the rate of concordance comprises dividing a number of matched events by a number of detected neurological events.

70. The IMD of claim 68 further comprising enabling the cardiac event detection signal to detect neurological events when the rate of concordance between the neurological and cardiac event detection signals exceeds the threshold.

71. The IMD of claim 70 wherein a therapy for treating neurological events is delivered to the patient in response to the detected cardiac events.

72. The IMD of claim 71 wherein the therapy comprises delivery of electrical stimulation to a brain of the patient.

73. The IMD of claim 66 further comprising

identifying a false positive event when one of the detected cardiac events is not temporally related to one of the detected neurological events,

calculating a false positive rate, the false positive rate being equal to a number of false positive events divided by a number of detected neurological events, and

enabling the cardiac event detection signal to detect neurological events when the false positive rate is below a predetermined level.

74. The IMD of claim 66 further comprising

identifying a false positive event when one of the detected cardiac events is not temporally related to one of the detected neurological events,

calculating a false positive rate, the false positive rate being equal to a number of false positive events per unit of time, and

enabling the cardiac event detection signal to detect neurological events when the false positive rate is below a predetermined level.

75. The IMD of claim 66 further comprising, for each of the matched events, determining a latency of the detected cardiac event with respect to a detected neurological event, and enabling the cardiac event detection signal to detect neurological events when the latency of the detected cardiac events meets a predetermined criterion.

76. The IMD of claim 66 further comprising calculating a false negative rate, the false negative rate being equal to a number of false negative events divided by a number of detected neurological events, and enabling the cardiac event detection signal to detect neurological events when the false negative rate is below a predetermined level.

77. The IMD of claim 66 wherein the neurological event detection signal is generated by a seizure detection algorithm which uses an EEG signal as an input, and wherein a matched event causes a modification of the seizure detection algorithm.

78. A computer-readable medium programmed with instructions for performing a method of comparing a cardiac event detection signal to a neurological event detection signal, the medium comprising instructions for causing a programmable processor to:

obtain a neurological event detection signal, the neurological event detection signal indicating detected neurological events in the patient;

obtain a cardiac event detection signal, the cardiac event detection signal indicating detected cardiac events in the patient;

analyze timing relationships between detected neurological events and cardiac events;

identify a matched event when one of the detected neurological events is temporally related to one of the detected cardiac events, and

indicate whether the cardiac event detection signal facilitates detection of neurological events based on the matched events.

79. A system for comparing a cardiac event detection signal to a neurological event detection signal, the system comprising:

communication means for obtaining a neurological event detection signal and a cardiac event detection signal, the neurological event detection signal indicating detected neurological events in the patient, the cardiac event detection signal indicating detected cardiac events in the patient;

a processor for analyzing timing relationships between detected neurological events and cardiac events, said processor being adapted to

identify a matched event when one of the detected neurological events is temporally related to one of the detected cardiac events, and

indicate whether the cardiac event detection signal facilitates detection of neurological events based on the matched events.