Ablation procedure
All patients provided their written informed consent before the ablation procedures. All patients received effective anticoagulation therapy with a direct oral anticoagulant for >1 month. Catheterization of the LA was performed using a 1-puncture 2-sheath technique. Unfractionated heparin was administered intravenously to maintain an activated clotting time of 300–350 s after the transseptal puncture. Thereafter, a 3.5-mm irrigated ablation catheter with contact force monitoring (ThermoCool Biosense Webster; Biosense Webster, Inc., Diamond Bar, CA, USA) and Pentaray Catheter (Biosense Webster, Inc.) were introduced through the sheaths. Bilateral circumferential PV isolation was performed using a 3D mapping system (CARTO3; Biosense Webster, Inc.). The radiofrequency current was delivered point-by-point for 30–35 s with a power of up to 35 W, a target temperature of <43°C, and an irrigation rate of 30 ml/min. The power of the radiofrequency current was limited to 25 W on the posterior wall close to the esophagus. The endpoint of PV isolation was bidirectional conduction block of the PVs identified by a multipolar catheter. If AF continued after this procedure, internal electrical cardioversion was performed. Additional ablation, such as that of the LA linear lesion (LA roof line and mitral isthmus line) and regions with complex fractionated electrograms, was performed if the AF could not be electrically cardioverted after PV isolation. After restoration of sinus rhythm, a cavotricuspid isthmus line was created with the endpoint of bidirectional conduction block in all patients. If there were non-PV foci under isoproterenol infusion (5–10 μg/min), we ablated them.