Patent ID: 7894885

Claim:
A method for monitoring an electrocardiogram (ECG) signal of a subject, comprising: digitally sampling an average signal from ECG electrodes attached to the subject, the average signal comprising a Wilson Central Terminal (WCT) signal; processing the WCT signal with a band-pass filter to establish a band-pass filter signal, the band-pass filter signal having a line interference component; processing the band-pass filter signal with a frequency meter and determining a frequency of the line interference component; determining an average interference frequency of the WCT signal based on the frequency of the line interference component; digitally sampling and buffering a raw ECG signal from another ECG electrode attached to the subject; calculating a moving average of the raw ECG signal; calculating a residual signal using the moving average of the raw ECG signal wherein the residual signal comprises frequency components at and above the average interference frequency; calculating, based on the residual signal, a first amplitude and a first phase shift of a primary interference signal at the average interference frequency and a second amplitude and a second phase shift of one or more harmonic interference signals at respective multiples of the average interference frequency; and digitally subtracting the primary interference signal and the one or more harmonic interference signals from the raw ECG signal so as to generate and output a clean ECG signal.