Deriving Patient Activity Information from Sensed Body Electrical Information

• US 20090156908A1
• Filed: 12/14/2007
• Published: 06/18/2009
• Est. Priority Date: 12/14/2007
• Status: Active Grant

• Current Assignee: Greatbatch Limited (Greatbatch Incorporated)
• Original Assignee: Transoma Medical, Inc.
• Inventors: Chen, Ji, Belalcazar, Andres
• Granted Patent: US 8,180,442 B2
• Time in Patent Office: Days
• US Class Current: 600/301
• 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 5/4519 Muscles A61B5/389, A61B5/224 take precedence

Abstract

Electrodes of a subcutaneous monitoring system receive body electrical signals that indicate both cardiac and non-cardiac muscle activity. In general, non-cardiac muscle activity is often correlated with physical activity, and physical activity is typically a strong indicator of patient health. Exemplary systems and methods that detect non-cardiac muscle activity information in sensed body electrical waveforms may provide a diagnostic tool for monitoring physical activity level over time in patients that have subcutaneous monitoring systems. In an illustrative embodiment, systems and methods for presenting patient activity information in a graphical format over intervals of time include processing ECG waveform information to identify and to accumulate non-cardiac muscular activity information during each of the intervals of time. In various implementations, number, intensity, and/or duration of the events that are identified during a time interval may be accumulated and stored for subsequent recall.

Claims

1. A method of storing information indicative of patient activity, the method comprising:

receiving an electrical waveform using subcutaneous electrodes, the received electrical waveform comprising electrical signals generated by electrical activity of a heart in a patient during a selected time period;

determining a value to represent a level of physical activity of the patient by identifying portions of the received electrical waveform that include signals indicative of non-cardiac muscular activity in the patient; and

storing the determined value in a data store for subsequent retrieval as an indicator of a level of physical activity of the patient during the selected time period.

2. The method of claim 1, further comprising sending the stored determined value for display on a display device in a histogram format to represent a measure of patient activity during the selected time period.

3. The method of claim 1, further comprising telemetering information indicative of non-cardiac muscle activity from a transmit module implanted in the patient to a receiver module external to the patient.

4. The method of claim 3, wherein the telemetered information comprises the stored determined value.

5. The method of claim 1, further comprising sending for display on a display device information about the values determined for each of a plurality of selected time periods.

6. A method of presenting physical activity information for an individual by detecting non-cardiac muscle noise in electrocardiogram (ECG) waveform information collected by an implanted device, the method comprising:

acquiring an electrical waveform representing electrical potentials between at least two subcutaneous electrodes during each of a plurality of non-overlapping time periods, the waveform being acquired by a medical device coupled to the at least two subcutaneous electrodes, the medical device being implanted substantially under the skin of a patient and arranged to receive and record electrical signals generated by cardiac activity in the body;

post-processing the acquired electrical waveform to determine a level of activity of the patient during each of the plurality of non-overlapping time periods by performing the following operations;

(a) selecting one of the plurality of non-overlapping time periods;

(b) identifying non-cardiac muscle activity events in the acquired electrical waveform that occurred during the selected time period;

(c) aggregating the activity events identified in operation (b) to determine a period activity value that represents a level of activity of the patient during the selected time period; and

(d) repeating operations (a)-(c) to select each of the time periods in the plurality of time periods; and

displaying to a user a representation of the period activity value for at least two of the plurality of time periods.

7. The method of claim 6, further comprising transmitting data representing the acquired electrical waveform through the skin from the implanted medical device to a receiver module external to the body.

8. The method of claim 7, wherein the receiver module comprises a programming module to store programming information for the medical device.

9. The method of claim 6, further comprising transmitting information about the period activity values through the skin from the implanted medical device to a receiver module external to the body.

10. The method of claim 9, wherein the receiver module comprises a programming module to store programming information for the medical device.

11. The method of claim 6, further comprising transmitting the acquired electrical waveform from a subcutaneous antenna implanted in the body.

12. The method of claim 6, wherein operation (b) further comprises high-pass filtering, rectifying, and smoothing the acquired electrical waveform.

13. The method of claim 6, wherein the operation (b) comprises comparing an amplitude of the waveform acquired during the selected time period to a threshold value.

14. The method of claim 13, wherein operation (b) further comprises comparing the acquired electrical waveform to at least one additional threshold value to identify non-cardiac muscle activity events in the acquired electrical waveform that occurred during the selected time period.

15. The method of claim 6, wherein operation (c) comprises counting the activity events identified in operation (b).

16. The method of claim 6, wherein the period activity value is a function of an amplitude of each of the activity events identified in operation (b).

17. The method of claim 6, wherein the period activity value is a function of a duration of each of the activity events identified in operation (b).

18. The method of claim 6, wherein the displayed representation comprises a histogram.

19. The method of claim 17, wherein, for each one of the plurality of time periods, the histogram represents in a first dimension a first period activity value based on a number of the activity events identified in operation (b), and further represents in a second dimension a second period activity value based on an amplitude of each of the activity events identified in operation (b).

20. The method of claim 17, wherein, for each one of the plurality of time periods, the histogram represents in a first dimension a first period activity value based on a number of the activity events identified in operation (b), and further represents in a second dimension a second period activity value based on a duration of each of the activity events identified in operation (b).

21. A system for presenting physical activity information for an individual by detecting non-cardiac muscle noise in electrocardiogram (ECG) waveform information collected by an implanted device, the system comprising:

an implantable waveform acquisition module operable to acquire ECG waveforms from subcutaneous electrodes implanted in a body;

a processing module to process the acquired ECG waveforms to identify non-cardiac muscle activity events;

an accumulation module to determine an activity level for each of a plurality of time intervals, each activity level being determined from an aggregation of the identified non-cardiac muscle activity events; and

a format module to render a graphical representation of the determined activity level for each of the plurality of time intervals.

22. The system of claim 21, further comprising a housing that contains the implantable waveform acquisition module and the processing module, the housing having an electrically conductive exterior portion that forms at least one of the subcutaneous electrodes.

23. The system of claim 22, wherein at least a portion of the electrically conductive exterior portion of the housing is adapted to make substantially direct electrical contact with non-cardiac muscle tissue.

24. The system of claim 23, wherein the non-cardiac muscle tissue comprises fascia.

25. The system of claim 22, wherein at least a portion of the electrically conductive exterior portion of the housing is substantially free of any electrically insulating coating when implanted in a body of a patient.

26. The system of claim 21, wherein the processing module receives the acquired ECG waveform from a receiver module located external to the body.

27. The system of claim 21, wherein the processing module is substantially remote from the body.

28. The system of claim 21, wherein the graphical representation comprises a histogram.

29. A method of controlling a rate of application of electrical stimulation to a heart of a patient based on patient activity as determined from non-cardiac muscle electrical signals in electrocardiogram (ECG) waveform information collected by an implanted device, the method comprising:

(a) receiving an electrical waveform using subcutaneous electrodes, the received electrical waveform comprising electrical signals generated by electrical activity of a heart in a patient during a selected time period;

(b) determining a level of physical activity of the patient by identifying portions of the received electrical waveform that include signals indicative of non-cardiac muscular activity in the patient during the selected time period; and

(c) adjusting a rate of electrical stimulation applied to the heart in response to changes in the determined level of physical activity.

30. The method of claim 29, wherein the determining step comprises post-processing the received electrical waveform to determine a level of activity of the patient during a portion of the selected time periods by identifying non-cardiac muscle activity events in the received electrical waveform and aggregating the identified activity events.

31. The method of claim 30, wherein the determining step further comprises counting the identified activity events to determine the level of activity of the patient.

32. The method of claim 30, wherein the determined level of activity of the patient is a function of an amplitude of each of the identified activity events.

33. The method of claim 30, wherein the determined level of activity of the patient is a function of a duration of one or more of the identified activity events.

34. The method of claim 29, wherein the adjusting step comprises adjusting the rate of electrical stimulation applied to the heart in response to a moving average of the determined physical activity level.

35. A system for applying electrical stimulus to an organ in a patient, the stimulation being responsive to patient physical activity information determined by detecting non-cardiac muscle noise in electrocardiogram (ECG) waveform information collected by a device implanted in the patient, the system comprising:

an implantable waveform acquisition module operable to acquire ECG waveforms from subcutaneous electrodes implanted in a body;

a first processing module to process the acquired ECG waveforms to identify non-cardiac muscle activity events;

a second processing module to determine an activity level from an aggregation of the identified non-cardiac muscle activity events; and

a stimulation module to generate electrical stimulation to apply to an organ in the body based on the determined activity level.

36. The system of claim 35, wherein the implantable waveform acquisition module comprises a housing having an electrically conductive exterior portion that forms at least one of the subcutaneous electrodes.

37. The system of claim 36, wherein at least a portion of the electrically conductive exterior portion of the housing is adapted to make substantially direct electrical contact with non-cardiac muscle tissue.

38. The system of claim 37, wherein the non-cardiac muscle tissue comprises fascia.

39. The system of claim 35, wherein at least a portion of the electrically conductive exterior portion of the housing is substantially free of any electrically insulating coating when implanted in the body.