Thromboembolism and bleeding are still the most common encountered complications during atrial fibrillation ablation. The purpose of this study is to investigate a prespecified protocol-driven continuous heparin infusion method comparing intermittent bolus method for an optimal activated clotting time (ACT) in patients during atrial fibrillation (AF) ablation in Asia population. This is a single-center and retrospective cohort study. The prespecified optimal ACT in this study is defined as 250-350 s. The primary outcome is the frequency of achieving optimal ACT during ablation. Safety outcomes are thromboembolic and major or minor bleeding events during or after ablation. Generalized Estimating Equations (GEE) logistic models will be used to analyze the factors associated with insufficient or over ACT events.