Intra-procedural setting
Electrophysiological study and ablation procedure was performed under conscious sedation with fentanyl and midazolam. A deflectable decapolar catheter was positioned in the coronary sinus (CS). An 8.5-French-long sheath (SL1; St. Jude Medical, Minnetonka, USA) was introduced into the LA using a modified Brockenbrough technique. To prevent thrombus formation, the transseptal sheath was continuously flushed with heparinized saline (20 mL/h) and i.v. heparin was administered to maintain an activated clotting time of 300–350 seconds. The LA was reconstructed under the guidance of a three-dimensional electroanatomic mapping system (CARTO, Biosense-Webster, Inc.) using a high-density mapping catheter (PENTARAY® Catheter Biosense-Webster Inc.). The catheter ablation was performed with a 3.5-mm cool saline-irrigated ablation catheter (Thermo-Cool SMARTTOUCH SF® Catheter. Biosense-Webster Inc, Diamond Bar, CA, USA). Point-by-point application was performed using power-control mode, with a temperature limited under 43°C and a saline irrigation rate of 8-30 mL/min. RF energy was delivered with a power output of 25 W in the CS and 35-50 W elsewhere. Radiofrequency applications were depicted using automated tagging technology (Carto VisiTagTM, Biosense Webster Inc.), with a filter threshold of catheter motion <2.5 mm within 4 seconds and contact force ≥8g for 70% of the time. Targets for ablation index (AI) were: (1) 500-550 for anterior wall; (2) 350-400 for posterior wall; (3) 450-500 for the LA roof and CTI; (4) 550-600 for MI.