Pacing-induced repolarization alternans within the pulmonary veins and its association with atrial fibrillation inducibility

Background Intracardiac electrogram-based repolarization alternans and its clinical significance have not been fully elucidated. Purpose This study aimed to determine the prevalence of pacing-induced repolarization alternans within the pulmonary veins (PVs) and to evaluate its association with atrial fibrillation (AF) inducibility. Methods We included 30 consecutive AF patients (median age, 75 years; 19 men; 18 paroxysmal and 12 persistent AF) undergoing catheter ablation for AF. Signal filtering was set at 0.05–500 Hz. Pacing was delivered from two different sites at each PV ostium at rates of 100 bpm, the maximum 1:1 atrioventricular conduction rate, and 200 bpm using a 64-pole basket mapping catheter (n=6) or a 48-pole 8-spline mapping catheter (n=24). Electrical alternans was defined as a beat-to-beat alternating morphology of the PV repolarization wave lasting for at least four consecutive cycles, as identified by visual inspection of intracardiac electrograms. Results Five patients were excluded from the analysis due to defibrillation failure (n=1) or incessant AF (n=4). AF was induced in 10 patients; a total of 11 AF episodes were documented, including eight originating from the left PV (LPV) and three from the right PV (RPV). Repolarization alternans was detected in 79.2% (19/24) of LPVs and 69.6% (16/23) of RPVs. PV repolarization alternans showed high sensitivity (87.5% for LPV, 100% for RPV) but low specificity (25% for LPV, 35% for RPV) for association with PV arrhythmogenicity. Repolarization alternans was never circumferentially distributed within any PV. Conclusions Pacing-induced repolarization alternans within the PV is a highly sensitive, but non-specific, marker of PV arrhythmogenicity. Given its regionally specific nature, intracardiac electrogram-based mapping of repolarization alternans may help identify arrhythmogenic substrates.Figure 1Figure 2