Detection of vasovagal syncope

• US 20040215263A1
• Filed: 04/23/2003
• Published: 10/28/2004
• Est. Priority Date: 04/23/2003
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Virag, Nathalie, Vetter, Rolf, Sutton, Richard
• Granted Patent: US 7,647,106 B2
• Time in Patent Office: Days
• US Class Current: 607/17
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/1116 Determining posture transitions
• CPC Class Codes: A61B 5/24 Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/4839 combined with drug delivery
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters

Abstract

It has been discovered that a change in posture that results in an increase in orthostatic stress, when followed by a withdrawal of sympathetic nervous activity, may indicate a future onset of vasovagal syncope (VVS). The invention is directed to devices and techniques for early detection of an episode of VVS so that therapies may be applied in advance of the episode to prevent the episode from occurring. Detection of a posture transition triggers a device such as an implanted pacemaker to determine an indicator of an autonomic nervous system activity of the patient. As a function of this determination, the device estimates a probability that the patient will experience VVS. When the probability exceeds a threshold, preventative therapy may be applied to address the VVS and to reduce the risk that the patient will faint.

Claims

1. A method comprising:

detecting a posture transition of a patient;

determining, in response to the posture transition, an indicator of an autonomic nervous system activity of the patient; and

estimating a probability that the patient will experience vasovagal syncope as a function of the determination.

2. The method of claim 1, wherein detecting a posture transition comprises detecting a posture transition that increases orthostatic stress.

3. The method of claim 1, wherein determining the indicator of the autonomic nervous system activity comprises determining a sympatho-vagal balance.

4. The method of claim 1, wherein determining the indicator of the autonomic nervous system activity comprises determining at least one of cardiac sympathetic nervous activity and cardiac parasympathetic nervous activity.

5. The method of claim 1, wherein determining the indicator of the autonomic nervous system activity comprises:

detecting at least one physiological signal that includes a sympathetic activity indicator and a parasympathetic activity indicator;

determining the sympathetic activity indicator;

determining the parasympathetic activity indicator; and

estimating the relative magnitude of the sympathetic activity indicator in comparison to the parasympathetic activity indicator.

6. The method of claim 5, further comprising:

detecting at least a second physiological signal that includes the sympathetic activity indicator and the parasympathetic activity indicator; and

applying blind source separation to the physiological signals to determine the sympathetic activity indicator and the parasympathetic activity indicator.

7. The method of claim 5, wherein the physiological signal comprises at least one of a heart rate, a heart interval and a blood pressure.

8. The method of claim 1, wherein determining the indicator of the autonomic nervous system activity comprises:

determining a baseline indicator of the autonomic nervous system activity; and

comparing the indicator to the baseline indicator.

9. The method of claim 8, wherein determining the baseline indicator of the autonomic nervous system activity comprises:

commencing a monitoring period in response to the detection of the posture transition; and

determining the baseline indicator of the autonomic nervous system activity during the monitoring period.

10. The method of claim 9, wherein the baseline indicator of the autonomic nervous system activity comprises a cumulative measure of the indicator of the autonomic nervous system activity and at least one physiological signal during the monitoring period.

11. The method of claim 9, wherein determining the baseline indicator comprises sensing at least one physiological signal.

12. The method of claim 11, wherein the physiological signal comprises at least one of a heart rate, a heart interval and a blood pressure.

13. The method of claim 9, further comprising:

sensing at least one physiological signal during the monitoring period;

generating a measure of the physiological signal as a function of the sensing during the monitoring period;

sensing the physiological signal following the monitoring period; and

normalizing the physiological signal following the monitoring period with respect to the measure.

14. The method of claim 8, further comprising normalizing the indicator to the baseline indicator.

15. The method of claim 8, wherein estimating a probability that the patient will experience vasovagal syncope comprises estimating the probability that the patient will experience vasovagal syncope as a function of the comparison.

16. The method of claim 1, further comprising:

sensing at least one physiological signal; and

determining the indicator of an autonomic nervous system activity of the patient as a function of the physiological signal.

17. The method of claim 1, further comprising:

comparing the estimated probability to a threshold; and

delivering therapy when the estimated probability exceeds the threshold.

18. The method of claim 17, wherein the therapy comprises at least one of cardiac pacing and drug delivery.

19. A computer-readable medium comprising instructions for causing a programmable processor to:

detect a posture transition of a patient;

determine, in response to the posture transition, an indicator of an autonomic nervous system activity of the patient; and

estimate a probability that the patient will experience vasovagal syncope as a function of the determination.

20. The medium of claim 19, wherein the instructions causing the processor to detect a posture transition of a patient comprise instructions causing the processor to detect a posture transition that increases orthostatic stress.

21. The medium of claim 19, wherein the instructions causing the processor to determine the indicator of the autonomic nervous system activity comprise instructions causing the processor to determine a sympatho-vagal balance.

22. The medium of claim 19, wherein the instructions causing the processor to determine the indicator of the autonomic nervous system activity comprise instructions causing the processor to determine at least one of cardiac sympathetic nervous activity and cardiac parasympathetic nervous activity.

23. The medium of claim 19, wherein the instructions causing the processor to determine the indicator of the autonomic nervous system activity comprise instructions causing the processor to:

detect at least one physiological signal that includes a sympathetic activity indicator and a parasympathetic activity indicator;

determine the sympathetic activity indicator;

determine the parasympathetic activity indicator; and

estimate the relative magnitude of the sympathetic activity indicator in comparison to the parasympathetic activity indicator.

24. The medium of claim 23, the instructions further causing the processor to:

detect at least a second physiological signal that includes the sympathetic activity indicator and the parasympathetic activity indicator; and

apply blind source separation to the physiological signals to determine the sympathetic activity indicator and the parasympathetic activity indicator.

25. The medium of claim 23, wherein the physiological signal comprises at least one of a heart rate, a heart interval and a blood pressure.

26. The medium of claim 19, wherein the instructions causing the processor to determine the indicator of the autonomic nervous system activity comprise instructions causing the processor to:

determine a baseline indicator of the autonomic nervous system activity; and

compare the indicator to the baseline indicator.

27. The medium of claim 26, wherein the instructions causing the processor to determine the baseline indicator of the autonomic nervous system activity comprise the instructions causing the processor to:

commence a monitoring period in response to the detection of the posture transition; and

determine the baseline indicator of the autonomic nervous system activity during the monitoring period.

28. The medium of claim 27, wherein the baseline indicator of the autonomic nervous system activity comprises a cumulative measure of the indicator of the autonomic nervous system activity and at least one physiological signal during the monitoring period.

29. The medium of claim 27, wherein the instructions causing the processor to determine the baseline indicator comprise instructions causing the processor to sense at least one physiological signal.

30. The medium of claim 29, wherein the physiological signal comprises at least one of a heart rate, a heart interval and a blood pressure.

31. The medium of claim 27, the instructions further causing the processor to:

sense at least one physiological signal during the monitoring period;

generate a measure of the physiological signal as a function of the sensing during the monitoring period;

sense the physiological signal following the monitoring period; and

normalize the physiological signal following the monitoring period with respect to the measure.

32. The medium of claim 26, the instructions further causing the processor to normalize the indicator to the baseline indicator.

33. The medium of claim 26, wherein the instructions causing the processor to estimate a probability that the patient will experience vasovagal syncope comprise instructions causing the processor to estimate the probability that the patient will experience vasovagal syncope as a function of the comparison.

34. The medium of claim 19, the instructions further causing the processor to:

sense at least one physiological signal; and

determine the indicator of an autonomic nervous system activity of the patient as a function of the physiological signal.

35. The medium of claim 19, the instructions further causing the processor to:

compare the estimated probability to a threshold; and

deliver therapy when the estimated probability exceeds the threshold.

36. The medium of claim 35, wherein the therapy comprises at least one of cardiac pacing and drug delivery.

37. A device comprising:

a first sensor to detect a posture transition of a patient;

a second sensor to sense a physiological signal that includes an indicator of autonomic nervous system activity; and

a processor to determine the indicator of autonomic nervous system activity and to estimate a probability that the patient will experience vasovagal syncope as a function of the determination.

38. The device of claim 37, wherein the first sensor comprises an accelerometer.

39. The device of claim 37, wherein the processor is further configured to determine a sympathetic activity indicator from a physiological signal, determine a parasympathetic activity indicator from the physiological signal and estimate the relative magnitude of the sympathetic activity indicator in comparison to the parasympathetic activity indicator.

40. The device of claim 39, further comprising a third sensor to sense a second physiological signal that includes an indicator of autonomic nervous system activity, wherein the processor is further configured to apply blind source separation to the first and second physiological signals to determine the sympathetic activity indicator and the parasympathetic activity indicator.

41. The device of claim 37, wherein the second sensor comprises at least one of a heart rate sensor, a heart interval sensor and a blood pressure sensor.

42. The device of claim 37, wherein the processor is further configured to commence a monitoring period in response to the detection of the posture transition by the first sensor and to determine a baseline indicator of the autonomic nervous system activity during the monitoring period.

43. The device of claim 42, wherein the processor is further configured to generate a measure of the physiological signal during the monitoring period.

44. The device of claim 37, further comprising a memory module to store a baseline indicator of the autonomic nervous system activity.

45. The device of claim 44, wherein the processor is further configured to compare the indicator to the baseline indicator and to estimate the probability that the patient will experience vasovagal syncope as a function of the comparison.

46. The device of claim 37, further comprising a therapy module, wherein the processor is further configured to control the therapy module to deliver therapy to the patient when the probability that the patient will experience vasovagal syncope exceeds a threshold.

47. The device of claim 46, wherein the therapy module comprises a drug delivery module.

48. The device of claim 46, wherein the therapy module comprises:

an implantable pulse generator to generate pacing pulses; and

at least one electrode coupled to the implantable pulse generator to deliver the pacing pulses to a heart of the patient.

49. The device of claim 37, wherein the device is implantable in a human body.