Optimal cancellation template analysis for ectopic beats removal in atrial fibrillation recordings

Ectopic beats are early heart beats notably different to the normal beat morphology. These beats are very common in atrial fibrillation (AF) being the source of important residua when ventricular activity is intended to be removed. Recently, their detection and clustering to build an efficient cancellation template, via principal component analysis (PCA), allowed us to obtain ECG signals with notably reduced ectopic residua. However, only the first principal component (PC) of the clustered ectopics was considered to build up the cancellation template. Hence, the effect of other PCs on cancellation performance has been evaluated in the present work. For this purpose, an index able to quantify the ectopic residue (ER) after cancellation was used. Results showed that cancellation in those cases where the first PC explained a variability of the clustered ectopics higher than 90% worsened when additional PC´s were included into the template. In contrast, for the abnormal beats in which the first PC explained a lower variability, a notable improvement in their cancellation was appreciated when the two first PCs were considered. In this respect, ER decreased from 0.537±0.041 to 0.396±0.041 when the second PC was considered together with the first one. Finally, considering the three first PCs also provided worse cancellation with respect to the previously analyzed cases. As a consequence, it could be considered that the second PC inclusion can improve cancellation of ectopics with rare morphologies.