Unipolar electrogram-based voltage mapping with far-field cancellation to improve detection of abnormal atrial substrate during atrial fibrillation.

INTRODUCTION An important substrate for AF is fibrotic atrial myopathy. Identifying low-voltage, myopathic regions during AF using traditional bipolar voltage mapping is limited by the directional-dependency of wave propagation. Our objective was to evaluate directionally-independent unipolar voltage mapping, but with far-field cancellation, to identify low-voltage regions during AF. METHODS In 12 patients undergoing pulmonary vein isolation for AF, high-resolution voltage mapping was performed in the left atrium during sinus rhythm and AF using a roving 20-pole circular catheter. Bipolar EGMs (Bi) <0.5mV in sinus rhythm identified low-voltage regions. During AF, bipolar voltage and unipolar voltage maps were created, the latter with (uni-res) and without (uni-orig) far-field cancellation using a novel, validated least-squares algorithm. RESULTS Uni-res voltage was ~25% lower than uni-orig for both low-voltage and normal atrial regions. Far-field EGM had a dominant frequency (DF) of 4.5-6.0Hz, and its removal resulted in a lower DF for uni-orig compared to uni-res (5.1±1.5Hz vs. 4.8±1.5Hz, p<0.001). Compared to Bi, uni-res had significantly greater area under the receiver operator curve (0.80 vs. 0.77, p<0.05), specificity (86% vs. 76%, p<0.001) and positive predictive value (43% vs. 30%, p<0.001) for detecting low-voltage during AF. Similar improvements in specificity and positive predictive value were evident for uni-res vs. uni-orig. CONCLUSION Far-field EGM can be reliably removed from uni-orig using our novel, least squares algorithm. Compared to Bi and uni-orig, uni-res is more accurate in detecting low-voltage regions during AF. This approach may improve substrate mapping and ablation during AF, and merits further study. This article is protected by copyright. All rights reserved.