Key result
A fourth-order high-pass Butterworth filter removed more baseline wander noise with no time delay compared to other filters, while power line interference filters had similar signal-to-noise ratios.
Why the study?
Preprocessing ECG signals with filters to denoise artifacts like power line interference and baseline wandering makes cardiac abnormality diagnosis and decision making simpler and faster.
A fourth-order high-pass Butterworth filter is optimal for removing baseline wander from ECG signals without introducing time delay.
The electrocardiogram (ECG), which represents the electrical activity of the heart, is always chosen as the basic signal for diagnosing cardiac abnormalities and detecting the patient's states. Generally, the various filters are applied (preprocessing) to denoise the artifacts from ECG signal. This step makes the decision making and diagnosis simpler and faster. The most common noise sources are power line interference and baseline wandering. This article discusses different filtering techniques used to denoise the ECG signals. Electrocardiogram signals were downloaded from the MIT-BIH Arrhythmia Database. The MIT-BIH Database was the first set of standard test materials that is generally available to evaluate arrhythmia detection. To remove baseline wander, 4 filters were designed. The filters are a fourth-order high-pass Butterworth filter, a second-order finite impulse response Hamming window, an finite impulse response rectangular window with length L, and an finite impulse response Hanning window. To extract the power line interference (60 Hz), 4 filters were designed: a second-order digital bandpass Butterworth filter, a second-order finite impulse response filter, a Chebyshev filter, and an finite impulse response notch filter with Hanning window. Finally, 5 parameters were used to evaluate filter performance; the parameters are frequency response, phase response, average filter delay (group delay), phase delay, and signal-to-noise ratio. The results show that, for baseline wander filters, a fourth-order high-pass Butterworth filter removes more noise and has no time delay. Power line interference filters have the same signal-to-noise ratio approximately.
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Mohamed et al. (2022) studied Cardiac Arrhythmias. ECG filtering techniques vs. Alternative filtering techniques was evaluated on Filter performance (frequency response, phase response, average filter delay, phase delay, and signal-to-noise ratio). A fourth-order high-pass Butterworth filter removed more baseline wander noise with no time delay compared to other filters, while power line interference filters had similar signal-to-noise ratios.
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