Power line interference removal from ECG signals using wavelet transform based component-retrieval

Power line interference (PLI) is a major source of noise in the ECG signal which can severely affect its interpretation. Moderate PLI can mask the finer features of the underlying signal whereas severe interference can completely overwhelm it. The techniques for PLI removal proposed in the literature are mostly based on fixed notch and adaptive filters. The fixed notch filters perform poorly in case of PLI frequency variations, whereas adaptive filters suffer from issues such as slow convergence and requirement of an external reference signal. In this paper, we propose an alternative approach for PLI removal from the ECG signal which overcomes the limitations of both fixed and adaptive filters. We model the PLI as an AM-FM component and use wavelet transform (WT) based component retrieval technique that is inspired by the synchrosqueezing framework to retrieve the PLI component, which is subtracted from the contaminated signal to remove the interference. The proposed method is evaluated in two worst-case scenarios of PLI frequency and amplitude variation, for healthy and pathological cases and the simulation results show significantly better performance of the proposed method over fixed and adaptive filtering techniques, as quantified by the performance indices.