A fast adaptive filter for electrocardiography

A new adaptive filter structure is proposed to reduce power line interference from ECGs. It is based on the principle of continuously tracking the frequency, amplitude and phase of the noise, using a modified form of the short time Fourier transform. This information is used to reconstruct the noise signal, which is then subtracted from the noisy ECG. The method was tested using ECGs from the MIT-BIH database with superimposed noise of varying amplitude and frequency (60 Hz +/- 5 Hz). It was found to be efficient even at low sampling rates. The process is computationally simple enough for real time implementation. It also obviates the need for a reference input. This technique can be applied to many other bipotential signals, and can be adapted for hardware implementation.