Impact of the extent of low-voltage zone on outcomes after voltage-based catheter ablation for persistent atrial fibrillation

Background: Low-voltage zones (LVZs), as measured by electroanatomic mapping, are thought to be associated with fibrosis. We reported the efficacy of atrial fibrillation (AF) ablation aiming to homogenize left atrial (LA) LVZ. The purpose of this study was to evaluate the impact of LVZ extension outcomes after LVZ homogenization in patients with nonparoxysmal AF. Methods: This prospective observational cohort study included 172 patients with nonparoxysmal AF undergoing their initial ablation. LVZ was defined as an area with bipolar electrograms <0.5 mV during sinus rhythm. LVZ extent was calculated as the percentage of LA surface area, and subsequently, LVZ was categorized into stages I (<5%), II (≥5% to <20%), III (≥20% to <30%), and IV (≥30%). Patients with LVZs underwent LVZ ablation aimed at homogenization of ≥80% of LVZs following pulmonary vein isolation. The primary endpoint was atrial tachyarrhythmia recurrence-free survival after a single procedure at 18 months off antiarrhythmic drugs. The association of %LVZ with recurrence-free survival was examined using Cox proportional hazard models. Results: The survival rates were 76%, 74%, 57%, and 28% in patients with stages I, II, III, and IV LVZ, respectively. The difference was significant between stages I and IV (log-rank, p < 0.001), while not significant between stages I vs. II and I vs. III (p = 0.843, p = 0.073, respectively). Cox proportional hazard model revealed that %LVZ was an independent predictor of recurrence-free survival (hazard ratio, 1.025 per 1% increase, p < 0.001; unadjusted model). The results were similar after demographic and clinical covariate adjustments and after excluding 12 patients who did not achieve homogenization of ≥80% of LVZ. Conclusions: The extent of LVZ is an independent predictor for recurrence even after LVZ homogenization.