ECG pace pulse detection and processing

• US 5,682,902 A
• Filed: 10/16/1995
• Issued: 11/04/1997
• Est. Priority Date: 10/16/1995
• Status: Expired due to Term

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Herleikson, Earl C.
• Primary Examiner(s): Jastrzab, Jeffrey R.
• Application Number:
  US08/543,738
• Time in Patent Office: 750 Days
• Field of Search: 128/697, 128/703, 128/704, 128/708, 128/901, 128/902, 607/27
• US Class Current: 600/521
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/7217 of noise originating from a therapeutic or surgical apparatus, e.g. from a pacemaker
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

A flexible ECG monitoring system including pace pulse detection. The monitoring system includes a potable monitor 102 that can be worn by a patient 120 or connected to a docking station 104. The portable monitor 102 includes an A/D converter 210, 208 and a digital signal processor 202. ECG signals are digitized and the digital signal processor derives a signal that is an estimate of the slope of the ECG signal. Pace pulses are detected by processing the slope signal, including use of a threshold that is dynamically updated based on the recent history of the slope signal. Detected pace pulses are removed prior to certain ECG filtering and reinserted following such filtering.

Claims

1. Apparatus for detecting pace pulses in an ECG signal comprising:

(A) means for processing the EGG signal to create a slope signal that is an estimate of the slope of the EGG signal;

(B) means for repeatedly determining and updating a slope threshold, where the slope threshold is determined based on analysis of the slope signal over a time interval that is less than the time between pace pulses to be detected;

(C) means for determining when the magnitude of the slope signal exceeds the threshold;

(D) means for detecting when a positive slope that has been identified as exceeding the threshold is within a particular a time of a negative slope that has been identified as exceeding the threshold, where the particular time is based on expected widths of pace pulses to be detected.

2. The apparatus of claim 1 wherein the threshold is about three times the peak value of the slope over the interval analyzed.

3. The apparatus of claim 1 wherein the particular time is about three milliseconds.

4. The apparatus of claim 1 further comprising means for creating a modified ECG signal in which a portion of the signal having a detected pace pulse is substantially modified.

5. The patient monitoring system of claim 4 wherein the means for creating a modified ECG signal:

(1) stores an initial threshold;

(2) replaces ECG data for a predetermined replacement period;

(3) in the replacement period, searches for a slope that exceeds the threshold, and if such slope is detected, extends the replacement period and replaces the initial threshold with a new value.

6. A method for analyzing an ECG signal from a patient to identify artifacts in the ECG signal resulting from artificial pacing of the patient'"'"'s heart, comprising the steps of:

(A) processing the EGG signal to create a slope signal that is an estimate of the slope of the ECG signal;

(B) determining when the magnitude of the slope signal exceeds a threshold;

(C) detecting when a positive slope that has been identified as exceeding the threshold is within a particular a time of a negative slope that has been identified as exceeding the threshold, where the particular time is based on expected widths of pace pulses to be detected;

(D) updating the threshold, where the threshold is determined based on analysis of the slope signal over a time interval that is less than the time between pace pulses to be detected.

7. A computer-readable memory configured so that it can be used to direct a computer to analyze an ECG signal according to the following steps:

(A) processing the ECG signal to create a slope signal that is an estimate of the slope of the ECG signal;

(B) determining when the magnitude of the slope signal exceeds a threshold;

(C) detecting when a positive slope that has been identified as exceeding the threshold is within a particular a time of a negative slope that has been identified as exceeding the threshold, where the particular time is based on expected widths of pace pulses to be detected;

(D) updating the threshold, where the threshold is determined based on analysis of the slope signal over a time interval that is less than the time between pace pulses to be detected.

8. A patient monitoring system comprising:

(A) ECG front-end for connecting to electrodes to measure an analog ECG signal from a patient and convert that analog ECG signal to a digital ECG signal;

(B) a pace pulse detector comprising

means for processing the digital ECG signal to create a slope signal that is an estimate of the slope of the ECG signal,

means for repeatedly determining and updating a slope threshold, where the slope threshold is determined based on analysis of the slope signal over a time interval that is less than the time between pace pulses to be detected,

means for determining when the magnitude of the slope signal exceeds the threshold,

means for detecting when a positive slope that has been identified as exceeding the threshold is within a particular a time of a negative slope that has been identified as exceeding the threshold, where the particular time is based on expected widths of pace pulses to be detected.

9. The patient monitoring system of claim 8 further comprising means for creating a modified ECG signal in which a portion of the signal having a detected pace pulse is substantially modified.

10. The patient monitoring system of claim 9 wherein the means for creating a modified ECG signal:

(1) stores an initial threshold;

(2) replaces ECG data for a predetermined replacement period;

(3) in the replacement period, searches for a slope that exceeds the threshold, and if such slope is detected, extends the replacement period and replaces the initial threshold with a new value.

11. The patient monitoring system of claim 9 wherein the means for creating a modified ECG signal:

(1) creates a modified ECG signal from which pace pulses have been substantially removed;

(2) filters the modified ECG signal;

(3) reinserts pace pulse data in the modified ECG signal.

12. The patient monitoring system of claim 9 wherein the means for creating a modified ECG signal replaces pace pulses with fixed pace pulses.

13. The patient monitoring system of claim 8 further comprising housing enclosing said pace-pulse detector and said ECG front-end and wherein the housing is adapted to be patient-borne.

14. The patient monitoring system of claim 13 wherein the further includes a wireless communication transmitter for transmitting the ECG data.