Catheter Ablation Procedure
The catheter ablation procedure was performed using a NavX system (St. Jude Medical, St. Paul, MN, USA) as described previously.10,13,18 A 5-french deflectable catheter was inserted into the coronary sinus (CS) via the right femoral vein. After a single transseptal procedure under intracardiac echocardiography guidance, an 8-F SL0 sheath and Agilis sheath (St. Jude Medical, St. Paul, MN, USA) were advanced into the LA. After the transseptal procedure, a single bolus of 5,000U of heparin was administered. A continuous infusion with heparinized saline was delivered to maintain an activated clotting time of 300 to 350s. The 3D LA geometry was created, and sequential contact mapping was performed using a 7-F decapolar circular catheter (EPstar Libero, Japan-lifeline Co.,Ltd., Tokyo, Japan). The whole LA was divided into eight areas (PVs, roof, left atrial appendage [LAA], septum, lateral, anterior, inferior, and posterior) for a location analysis of the AF substrate. 10,13,18 The mapping points in each region were similar in number and nearly equally distributed (LA mean mapping points: 1843± 501).
The PVI was performed guided by a 7-F decapolar circular catheter positioned at the PV ostia as described previously.10,13,18 Each radiofrequency (RF) energy application was delivered for 40s. A 3.5mm irrigated tip RF catheter (FlexAbility TM, St. Jude Medical Inc.) was used with the temperature limited to 42℃ and power to 30W (25W to sites near the esophagus) with a flow rate of 13 mL/min. After the elimination or dissociation of the PV potentials, exit block was confirmed by pacing from the circular catheter placed within the PVs. After the PVI, DF mapping and rotor mapping were simultaneously performed in the same mapping area as follows. Finally, a LA voltage map was performed during pacing from the distal CS after external cardioversion.
Once in SR, decremental pacing (10 milliseconds steps from 250 to 200 miliseconds, over a period of 10 seconds) at an output of 10mA and 2ms pulse width was performed from the distal CS once, in an attempt to induce an atrial tachyarrhythmia without an isoproterenol injection. An induced AF/atrial tachycardia (AT) was defined as that sustained for at least 2 minutes.17 When AF/AT continued, external cardioversion was performed. When cavotricuspid isthmus (CTI) dependent AFL was induced, a CTI ablation was performed.