A Least Squares Approach to Estimation of Far-field Voltage in Unipolar Electrograms in Atrial Fibrillation

The evaluation of atrial scar using electrogram voltage is emerging as a promising approach to atrial fibrillation catheter ablation. However, unipolar electrograms recorded from intracardiac catheters during AF are corrupted by far-field signals from remote atrial sites and the ventricles, which results in voltage overestimation and scar underdetection. Removal of these far field signals would allow improved assessment of the local unipolar electrogram at the recording site. Most far-field removal methods consider only the ventricular far-field. In AF, the surrounding right and left atrial activity contributes to the far field and its removal has not been previously described. We present a least squares method to remove the far-field from all sources from unipolar electrograms. We tested the method on synthetic data generated from real electrograms from 80 patients undergoing AF catheter ablation. The method performed well, extracting the far-field with high accuracy.