Cancellation of ventricular activity in unipolar endocardial recordings during atrial fibrillation

Atrial fibrillation (AF) arises from complex spa-tiotemporal atrial activation. Unipolar electrogram (EGM) analysis of atrial activity may improve our understanding of AF mechanisms, but these recordings are typically obscured by large far-field ventricular activity. It is therefore necessary to separate atrial activity from ventricular activity in the recorded unipolar EGM. In this paper, the detection of AF from unipolar EGMs recorded along the left atrial endocardium is considered for the first time. A simple method is proposed to compute the average ventricular activity, and this template is subtracted from the source unipolar EGMs in order to detect AF in the residual signal. The reliability of AF discrimination with low magnitude AF and when it coincides with ventricular activity is evaluated using simulated and real unipolar EGMs. The results from the simulated EGM database show that the median concordance between detected AF and simulated AF is 0.61.