Filters for the reduction of baseline wander and muscle artifact in the ECG.

Contamination of the electrocardiographic (ECG) signal by extraneous electrical potentials is a significant problem in exercise electrocardiography. Baseline wander and muscle artifact are particularly troublesome sources of interference. This paper describes two digital filters that were constructed and found effective in reducing these two types of signal contamination. The baseline wander filter presented here is a linear phase high-pass filter having a cutoff frequency lower than the heart rate. The low computational overhead makes this filter practical for multiple channel implementation on a low-cost digital signal processor. Because the muscle artifact signal, generated by skeletal muscle activity, occupies the same spectrum space as the heart-generated signal, spectral filtering is not very effective in eliminating it. Described here is a time-varying filter that employs a combination of linear and nonlinear filtering techniques.