Cardiac catheterization
All patients underwent the catheter ablation procedure in the fasting state under local anesthesia and conscious sedation with dexmedetomidine hydrochloride and thiamylal sodium. Respiratory management devices including nasal airway device and adaptive servo-ventilation were used at the operator’s discretion. A 6Fr, double-decapolar, steerable catheter (BeeAT, Japan Lifeline Co, Tokyo, Japan) was inserted into the coronary sinus via the right internal jugular vein. An 8 Fr Carto SoundStar® was inserted into the right atrium via the right femoral vein, and the LA 3-dimensional (3D) geometry was created by CartoMergeTM module equipped in a Carto3 system (Biosense Webstar) which was thereafter integrated with the 3D LA CT image which was taken approximately one week before the study. After the transseptal puncture done under the ICE guidance, we inserted two 8.5Fr long sheaths (SL0; St Jude Medical, St Paul, MN) or SL0 sheath plus 8.5Fr steerable sheath (AgilisTM; Abott, Chicago, Illinois) into the LA. For intraoperative anticoagulation, we injected 3000 units of heparin before and 5000 units just after the transseptal puncture, followed by repetitive injection of 1000 to 2000 units of heparin to maintain an activated clotting time greater than 300 seconds during the procedure.