First-pass isolation and procedural metrics associated with catheter ablation outcomes for atrial fibrillation: a retrospective cohort study.

Background: First-pass isolation (FPI) during pulmonary vein isolation (PVI) is an acute procedural endpoint that may reflect the quality of initial lesion delivery and has been proposed as a predictor of durable ablation success. This study aimed to evaluate the association between FPI and post-ablation outcomes, identify factors associated with FPI achievement, and determine whether procedural metrics add prognostic information beyond conventional clinical variables in atrial fibrillation (AF) patients. Methods: This retrospective cohort study included 313 AF patients undergoing first-time radiofrequency catheter ablation between August 2023 and January 2025. Patients were classified into two groups: those without FPI in either ipsilateral PVs (NEITHER, Results: FPI was achieved in 64.5% (404/626) of ipsilateral PV circles. Higher C3-FOT ratio was independently associated with greater FPI achievement, whereas right-sided PV location and higher gap number were associated with reduced FPI achievement. During a median follow-up of 21.1 months, 81 patients (25.9%) experienced recurrence. The NEITHER group had lower recurrence-free survival than the IFPI group (log-rank Conclusions: IFPI was independently associated with a lower risk of atrial arrhythmia recurrence, while FPI achievement was related to favorable procedural characteristics including lower gap burden and higher C3-FOT ratio.