Baseline Wander Removal and Isoelectric Correction in Electrocardiograms Using Clustering

Baseline wander is a low frequency noise which is often removed by a highpass filter in electrocardiogram signals. However, this might not be sufficient to correct the isoelectric level of the signal, there exist an isoelectric bias. The isoelectric level is used as a reference point for amplitude measurements, and is recommended to have this point at 0 V, i.e. isoelectric adjusted. To correct the isoelectric level a clustering method is proposed to determine the isoelectric bias, which is thereafter subtracted from a signal averaged template. Calculation of the mean electrical axis (MEA) is used to evaluate the iso-electric correction. The MEA can be estimated from any lead pairs in the frontal plane, and a low variance in the estimates over the different lead pairs would suggest that the calculation of the MEA in each lead pair are consistent. Different methods are evaluated for calculating MEA, and the variance in the results as well as other measures, favour the proposed isoelectric adjusted signals in all MEA methods.