Ablation procedure
A 4-mm-tip open-irrigated ablation catheter with three 1-mm minielectodes located laterally at the tip (IntellaNav MiFi OI®; Boston Scientific) was used. The catheter can measure real-time LI calculated from a local electric field generated at the tip of the ablation catheter. During the procedure, the operators were blinded to LI measurements.
Circumferential ablation around an ipsilateral PV was performed using a point-by-point technique. Radiofrequency energy was applied for > 20 sec at each site using a maximum temperature of 42 °C and maximum power of 35 W. The irrigation rate was 17 mL/min. RFA was stopped when the catheter moved, esophageal temperature rose to 40 °C, or bradycardia was induced. The ablation point was marked with a 4-mm-diameter point tag. After completing a >20-sec RFA, the catheter tip was moved to the next ablation point, located approximately 4.0 mm from the adjacent point (Figure 1).
After completing circumferential PV ablation, left and right ipsilateral PV were mapped using the basket catheter, and electrical conduction inside the ipsilateral PV was analyzed. If left atrium to PV conduction was present, RFAs targeting conduction gaps on the circumferential line were delivered until left atrium to PV conduction was eliminated.9 Creation of sufficient ablation lesions was assessed by the absence of a conduction gap.