A method for reduction of power line interference in the ECG

A method for reduction of power line interference (PLI) in electrocardiograms with sampling rate integer multiple of the nominal power line frequency is developed and tested using simulated signals and records from the databases of the American Heart Association and the Massachusetts Institute of Technology. The method involves parabolic detrending of the ECG, estimation of the signal components with frequencies corresponding to PLI by discrete Fourier transform, and minimum-squared-error approximation of decimated series of averaged instantaneous values of PLI using appropriately defined weights. Tests of the proposed method with simulated data show that for signal-to-noise ratios SNR greater than 25 dB, the logarithmic relative error is below -32 dB and the error-to-signal ratio is less than -24 dB. For lower SNR, the errors increased, and a noise attenuation of 0.6 dB is observed. The main advantage of the developed method in comparison with other simpler and faster approaches is the accurate interference reduction in cases when the power line frequency deviates from the nominal 50 or 60 Hz. Due to computational burden, the method is more suitable for off-line application, but real-time implementation, using modern processors, is also possible.