Combined bipolar and unipolar voltage mapping to identify epicardial breakthrough regions after pulsed field ablation

The utility of unipolar voltage (UV) mapping for identifying epicardial breakthrough regions after pulmonary vein isolation (PVI) remains undetermined. This study assessed combined bipolar voltage (BV) and UV mapping for identifying epicardial breakthrough regions after pulsed field ablation (PFA). Thirty patients with atrial fibrillation underwent initial PFA-PVI with a pentaspline catheter under fluoroscopic guidance. Within the isolated PV antrum (BV <0.1 mV), transmurally ablated regions and epicardial breakthrough regions were defined by UV <1.08 mV and UV ≥1.08 mV, respectively. Unipolar electrogram features were investigated to identify epicardial breakthrough regions. Seventeen patients had 27 epicardial breakthrough regions, yielding 276 local unipolar electrograms (QR pattern: n=160; RS pattern: n=116). QR electrograms were distributed broadly within the isolated PV, whereas RS electrograms occurred exclusively around the isolation boundary. QR electrograms, indicating possible epicardial breakthrough, had significantly higher UV amplitudes than RS electrograms (median: 1.64 vs. 0.70 mV; P<0.001). The UV amplitude cutoff distinguishing these morphologies was 1.15 mV (sensitivity, 91.9%; specificity, 84.5%; area under the curve [AUC], 0.922; P<0.001). Among 245 local unipolar electrograms around the isolation boundary, excluding QR electrograms, RS electrograms had higher UV amplitudes and steeper negative intrinsic deflection slopes than non-RS electrograms, suggesting possible intramural conduction gaps. Respective cutoffs were 0.48 mV (sensitivity, 83.6%; specificity, 86.8%; AUC, 0.923; P<0.001) and 0.020 mV/ms (sensitivity, 97.4%; specificity, 94.5%; AUC, 0.992; P<0.001). Combined BV and UV mapping provides additional information for identifying epicardial breakthrough regions at PFA application sites.