Muscle artifact noise detector for ECG signals

• US 5,999,845 A
• Filed: 05/20/1998
• Issued: 12/07/1999
• Est. Priority Date: 05/21/1997
• Status: Expired due to Term

• Current Assignee: Mortara Instrument, Inc. (Baxter International Inc.)
• Original Assignee: Quinton Instrument Co. (Cardica Incorporated)
• Inventors: dePinto, Victor M.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): EVANISKO, GEORGE ROBERT
• Application Number:
  US09/081,950
• Time in Patent Office: 566 Days
• Field of Search: 128/901, 600/508, 600/509, 600/521, 600/522
• US Class Current: 600/509
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: H03D 7/165 at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature combined with amplitude demodulation H03D1/2245, combined with angle demodulation H03D3/007; N-path filters H03H19/002
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

A filter system for detecting and removing small amplitude, high frequency signals such as muscle artifact signals is provided. One form of the system includes a baseline wander filter, high and low pass filters, an adaptive line noise canceler and various noise detectors to identify, signal and remove muscle artifact or loose electrode signal contamination from an ECG signal wherein the ECG signal is conditioned to remove various portions of the ECG signal, such as the QRS portion of the ECG signal, prior to processing in various noise detectors while minimizing the signal conditioning effect of the filters on the ECG signal and while further providing the operator with the ability to manually or automatically activate the filters and to indicate the status of the filters on a printout or display.

Claims

1. A device for detecting wide band noise from an ECG signal including a QRS portion received from a patient comprising:

an ECG signal input for receiving the ECG signal including a QRS portion;

an ECG gate circuit blanking said ECG signal from a point in time prior to an onset of the QRS portion of said ECG signal and ending at a point in time after an end of the QRS portion so that the QRS is removed;

a high pass filter filtering said ECG signal to form a high pass filtered ECG signal with the QRS portion removed; and

a wideband noise detector detecting a level of noise in said high pass filtered ECG signal with the QRS portion removed.

2. The device of claim 1 wherein said device further includes an adaptive line noise canceller removing line noise from said ECG signal, said adaptive line noise canceller being coupled between said ECG signal input and said high pass filter.

3. The device of claim 1 wherein said ECG gate circuit further includes an ECG gate signal derived from said ECG signal and a switch means responsive to said ECG gate signal for preventing the QRS portion of said ECG signal from being detected by said wideband noise detector.

4. The device of claim 1 wherein said device further includes a baseline wander filter to remove baseline wander from said ECG signal prior to said wideband noise detector.

5. The device of claim 1 wherein said high pass filter allows ECG signal frequencies above about 40 Hz to pass therethrough.

6. The device of claim 1 wherein said wideband noise detector has an output producing an indication signal that is an estimate of the amount of high frequency energy in said ECG signal.

7. A device for detecting muscle artifact noise in an ECG signal comprising:

an ECG signal input for receiving an ECG signal having a QRS portion from a patient;

an ECG gate signal derived from said ECG signal, said ECG gate signal beginning prior to an onset of the QRS portion of said ECG signal and ending at a point in time after the end of the QRS portion;

means, connected to said input, for attenuating and delaying predetermined frequency components of said ECG signal to filter said ECG signal;

switch means for allowing for the selective passage of said ECG signal therethrough in response to said ECG gate signal; and

detector means, connected selectively through said switch means to said means for attenuating and delaying, for measuring wideband noise of said ECG signal which passes selectively through said switch means.

8. The device of claim 7 further including visual indication means responsive to said detector means for an indication to operator of the device that wideband noise exists in said ECG signal.

9. The device of claim 7 wherein said detector means further includes a wideband noise detector circuit and said wide band noise detector circuit includes a signal averaging system therein.

10. The device of claim 7 further including a means connected to said switch means for stretching said ECG gate signal timewise to lengthen the time said switch means allows such selective passage.

11. The device of claim 7 further including a wideband noise detector curcuit and means for inhibiting the operation of said wideband noise detector circuit while said switch means allows such selective passage.

12. A device for detecting noise from an ECG signal comprising:

an ECG signal input for receiving an ECG signal from a patient;

an ECG gate signal for blanking a portion of said ECG signal from a point in time prior to the onset of the QRS portion of said ECG signal and ending at a point in time after the end of the QRS portion;

a switch member connected to said ECG input for allowing said ECG signal to selectively pass therethrough and blanking said ECG signal in response to said ECG gate signal; and

a wideband noise detector for measuring wideband noise from said ECG signal having the QRS portion blanked wherein said wideband noise detector receives said ECG signal through said switch member.

13. The device of claim 12 wherein said switch member inhibits the passage of said ECG signal through said wideband noise detector.

14. The device of claim 12 wherein said switch member inhibits the passage of said ECG signal through said wideband noise detector during the QRS portion of said ECG signal.

15. The device of claim 12 further including a high pass filter to allow the high frequency portion of said ECG signal to pass therethrough and to said wideband noise detector.

16. The device of claim 12 further including an adaptive line noise canceler therein having a high pass filter therein to filter said ECG signal prior to said wideband noise detector.

17. A method for detecting noise from an ECG signal comprising:

providing an ECG signal input for receiving an ECG signal from a patient;

providing an ECG gate signal for blanking a portion of said ECG signal from a point in time prior to the onset of the QRS portion of said ECG signal and ending at a point in time after the end of the QRS portion;

providing the ECG signal and ECG gate signal to a switch member which is selectively opened and closed in response to said ECG gate signal to selectively allow said ECG signal to pass therethrough;

providing a wideband noise detector to measure the high frequency noise in the ECG signal following the switch member.

18. The method of claim 17 wherein the wideband noise detector measures the high frequency noise in the ECG signal after removing a QRS portion of the ECG signal.

19. The method of claim 17 wherein the ECG signal is filtered with a high pass filter following the switch member to allow the portion of the ECG signal having energy greater than 40 Hz to be presented to wideband noise detector.