ELECTROCARDIOGRAPHIC R-WAVE DETECTOR

• US 3,590,811 A
• Filed: 12/06/1968
• Issued: 07/06/1971
• Est. Priority Date: 12/06/1968
• Status: Expired due to Term

• Current Assignee: Warner-Lambert Company (Pfizer Inc.)
• Original Assignee: George J. Harris
• Inventors: Harris, George J.
• Application Number:
  US04/781,896
• Time in Patent Office: 942 Days
• US Class Current: 600/521
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/308 for electrocardiography [ECG]
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval

Abstract

An electrocardiographic R-wave detection circuit in which the ECG. signal is applied to one input of a comparator. The threshold level, applied to the other input of the comparator, is below the peak of the R-wave, and above the peaks of the P and T waves. The amplitude of the ECG. signal can vary over a wide range depending upon the placement of electrodes, etc. For this reason, the threshold level is continuously adjustable in accordance with the peak swing of the input signal. The threshold level is a fraction of the peak signal swing, the selected fraction being such that the threshold level always falls between the peak of the R-wave and the peaks of the P- and T-waves. The threshold level adjustment circuit has a time constant of approximately 10 seconds. The circuit is thus enabled to operate linearly over a very wide range of signal magnitudes.

Claims

1. In electrocardiographic monitoring equipment, an R-wave detection circuit comprising means for attenuating the low frequency components with respect to the high frequency components in an electrocardiographic signal to form a signal having one or more peaks corresponding to the QRS complex in each electrocardiographic waveform, means for deriving a threshold level which is a fraction of the peak amplitude of the formed signal averaged out over a number of cycles, said fraction having a value such that said threshold level is below at least one of the peaks in the formed signal corresponding to the QRS complex in the electrocardiographic waveform and above any peaks in the formed signal corresponding to the P- and T-waves in the electrocardiographic waveform, means for comparing the instantaneous value of said formed signal to said threshold level, and indicating means responsive to the operation of said comparing means for indicating occurrence of said QRS complex.

2. Monitoring equipment in accordance with claim 1 wherein said indicating means further includes means responsive to said comparing means for generating a single output signal during a comparison in which one or more of the peaks in said formed signal exceed said threshold level.

3. Monitoring equipment in accordance with claim 1 further including means for rectifying said formed signal prior to the application of said formed signal to said comparing means and to said threshold level deriving means.

4. Monitoring equipment in accordance with claim 2 further including means for rectifying said formed signal prior to the application of said formed signal to said comparing means and to said threshold level deriving means.

5. Monitoring equipment in accordance with claim 1 and wherein said threshold level deriving means includes a peak detector for repetitively detecting peak values of repetitive QRS complexes, each of said detected peak values being related to one of said QRS complexes, and a voltage divider operatively connected to said peak detector for providing a fractional amount of each of said detected peak values, said fractional amount being proportional to said threshold level.