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.