EP Study and Ablation Procedure
All procedures were performed in the fasting state under general anesthesia with mechanical ventilation through a laryngeal mask airway. After introducing the vascular access, intravenous heparin was initiated to maintain the activated coagulation time over 300 seconds throughout the procedure.
A duodecapolar catheter (BeeATâ„¢, Japan Lifeline Co., Tokyo, Japan) was placed in the coronary sinus (CS) through the right internal jugular vein. The proximal eight electrodes of this catheter covered the septum of the right atrium (RA) and superior vena cava (SVC). We performed transseptal puncture with the guidance of the intracardiac ultrasound. After the puncture, a single 8.5 Fr steerable catheter (Agilis, St. Jude Medical, St. Paul, MN, USA) and two pre-shaped catheters (8Fr SL0, St. Jude Medical, St. Paul, MN, USA) were inserted into the left atrium (LA). Three-dimensional electroanatomic mapping system (EnSite NavX, St. Jude Medical, St. Paul, MN, USA and Carto 3, Biosense Webster, Irvine, CA, USA) were used in all patients.
All patients underwent PV isolation with or without posterior wall isolation (i.e., BOX isolation). We preferentially performed BOX isolation; however, considering the type of AF (paroxysmal or non-paroxysmal) and the spatial relationship between the esophagus and the LA posterior wall, a standard PV isolation was adopted in some patients. The ablation catheter and double Lasso mapping catheters were each advanced into the LA. Radiofrequency (RF) ablation was applied via an irrigated tip catheter to encompass the left and right PVs for PV isolation and encompass all PVs together with the posterior wall for BOX isolation. The endpoint of the PVI and BOX isolation was a bidirectional conduction block between the LA and each isolation area.
SVC isolation was also performed in patients who has long SVC myocardial sleeve (> 2 cm). The endpoint of SVC isolation was a bidirectional conduction block between RA and SVC. To prevent diaphragmatic paralysis, we performed pace mapping to identify the site with diaphragmatic capture. RF ablation was applied in a point-by-point manner at the earliest activation site of SVC potentials during sinus rhythm.
Cavotricuspid isthmus (CTI) ablation was performed in all patients except for the patients who underwent a prior ablation procedure for AF. The endpoint of CTI ablation was a bidirectional conduction block across the CTI.
The other ablation strategies such as linear ablation, ablation targeting complex atrial fractionated electrocardiogram (CFAE), or low voltage area were at the operator’s discretion.