Distributed cardiac activity monitoring with selective filtering

• US 20070156054A1
• Filed: 07/31/2006
• Published: 07/05/2007
• Est. Priority Date: 02/17/2004
• Status: Abandoned Application

• Current Assignee: Cardionet Incorporated
• Original Assignee: Cardionet Incorporated
• Inventors: Korzinov, Lev, Cybulski, Zach, Churchville, Dave
• Application Number:
  US11/497,542
• Publication Number:
  US 20070156054A1
• Time in Patent Office: Days
• US Class Current: 600/509
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

System and techniques for distributed monitoring of cardiac activity include selective T wave filtering. In general, in one implementation, a distributed cardiac activity monitoring system includes a monitoring apparatus, with a selectively activated T wave filter, and a monitoring station. The monitoring apparatus can include a communications interface, a real-time QRS detector, a T wave filter, and a selector that activates the T wave filter to preprocess a cardiac signal provided to the real-time QRS detector in response to a message. The monitoring station can communicatively couple with the monitoring apparatus, over a communications channel, via the communications interface and can transmit the message to the monitoring apparatus to activate the T wave filter based at least in part upon a predetermined criteria (e.g., abnormal T waves for an individual, as identified by a system operator).

Claims

1. A machine-implemented method comprising:

identifying heart beats in a sensed cardiac signal;

activating a T wave filter, used in said identifying heart beats, in response to a message from a monitoring station generated at least in part based upon discovery of a predetermined characteristic in the sensed cardiac signal; and

outputting information corresponding to the identified heart beats to a communications channel of a distributed cardiac activity monitoring system.

2. The method of claim 1, wherein said identifying heart beats comprises identifying R waves in the sensed cardiac signal.

3. The method of claim 1, further comprising sending at least a portion of the sensed cardiac signal to the monitoring station, and wherein the discovery of the predetermined characteristic comprises identification of a tall T wave in the at least a portion of the sensed cardiac signal by an operator at the monitoring station.

4. The method of claim 1, wherein said activating the T wave filter comprises activating a filter that reduces signal amplitude at low frequencies of the sensed cardiac signal.

5. The method of claim 4, wherein the filter has a frequency response of about 0 dB or more at frequencies above ten Hertz.

6. The method of claim 5, wherein the filter has a frequency response of about −

10 dB or less in a low frequency range of zero to five Hertz.

7. The method of claim 6, wherein the filter has a frequency response of about +2 dB or more in a high frequency range of twenty to twenty five Hertz.

8. The method of claim 1, wherein said outputting information comprises outputting heart rate data to a wireless communications channel.

9. The method of claim 1, further comprising:

determining that an abnormal T wave is possible based on signal morphology analysis; and

notifying a system operator of the possible abnormal T wave.

10. The method of claim 1, further comprising deactivating the T wave filter in response to a second message.

11. A distributed cardiac activity monitoring system comprising:

a monitoring apparatus including a communications interface, a real-time QRS detector, a T wave filter, and a selector that activates the T wave filter with respect to the real-time QRS detector in response to a message, wherein the activated T waver filter preprocesses a cardiac signal provided to the real-time QRS detector; and

a monitoring station that communicatively couples with the monitoring apparatus via the communications interface and transmits the message to the monitoring apparatus to activate the T wave filter based at least in part upon a predetermined criteria.

12. The system of claim 11, wherein the communications interface comprises a wireless communications interface.

13. The system of claim 11, wherein the T wave filter comprises a filter that reduces signal amplitude at low frequencies.

14. The system of claim 13, wherein the filter has a frequency response of about −

10 dB or less in a low frequency range of zero to five Hertz.

15. The system of claim 13, wherein the filter has a frequency response of about 0 dB or more at frequencies above ten Hertz.

16. The system of claim 15, wherein the filter has a frequency response of about +2 dB or more in a high frequency range of twenty to twenty five Hertz.

17. The system of claim 11, wherein the selector comprises analog, selective activation circuitry.

18. The system of claim 11, wherein the monitoring apparatus further comprises additional logic that determines if an abnormal T wave is possible based on signal morphology analysis, and notifies a system operator of the possible abnormal T wave.

19. The system of claim 11, wherein the monitoring station further comprises additional logic that determines if an abnormal T wave is possible based on signal morphology analysis, and notifies a system operator of the possible abnormal T wave.

20. A cardiac monitoring apparatus comprising:

a communications interface;

a real-time heart beat detector;

a T wave filter; and

a selector that activates the T wave filter with respect to the real-time heart beat detector in response to a message, wherein the activated T waver filter preprocesses a cardiac signal provided to the real-time heart beat detector.

21. The apparatus of claim 20, wherein the communications interface comprises a wireless communications interface.

22. The apparatus of claim 20, wherein the real-time heart beat detector comprises an analog heart beat detector, the T wave filter comprises an analog T wave filter, and the selector comprises analog, selective activation circuitry.

23. The apparatus of claim 20, wherein the T wave filter comprises a filter that reduces signal amplitude at low frequencies.

24. The apparatus of claim 23, wherein the filter has a frequency response of about −

10 dB or less in a low frequency range of zero to five Hertz.

25. The apparatus of claim 24, wherein the filter has a frequency response of about 0 dB or more at frequencies above ten Hertz.

26. The apparatus of claim 25, wherein the filter has a frequency response of about +2 dB or more in a high frequency range of twenty to twenty five Hertz.

27. The apparatus of claim 20, further comprising additional logic that determines if an abnormal T wave is possible based on signal morphology analysis, and notifies a system operator of the possible abnormal T wave.

28. A method comprising:

receiving at least a portion of a sensed cardiac signal from a monitoring apparatus in contact with a living being under active cardiac monitoring;

identify an abnormal T wave in the received cardiac signal; and

sending a message to the monitoring apparatus over a communications channel, the message causing the monitoring apparatus to activate a T wave filter used in identifying heart beats of the living being under active cardiac monitoring.

29. The method of claim 28, further comprising:

determining that an abnormal T wave is possible based on signal morphology analysis; and

notifying a system operator of the possible abnormal T wave, wherein the system operator performs said identifying the abnormal T wave.

30. The method of claim 28, wherein said sending the message comprises sending the message over a wireless communications channel.

31. The method of claim 28, further comprising installing the T wave filter into the monitoring apparatus, which comprises a preexisting beat detector.

32. A system comprising:

means for identifying heart beats in a sensed cardiac signal;

means for filtering the sensed cardiac signal to reduce T waves in the sensed cardiac signal; and

means for selectively activating the means for filtering in response to discovery of a predetermined characteristic in the sensed cardiac signal.

33. The system of claim 32, further comprising means for alerting a system operator of a possible abnormal T wave.

34. The system of claim 32, wherein the means for filtering comprises means for generally highpass filtering.