The investigators will compare the ablation time during pulmonary vein isolation of Ablation Index-guided high power ablation with those with conventional ablation.

Ablation time of conventional group will be used from OPTIMUM study. For secondary outcomes, acute outcomes of pulmonary vein isolation using two different strategies will be compared. During 1 year of follow-up in both groups, atrial fibrillation recurrence will be evaluated. The atrial fibrillation recurrence rate at 1 year after pulmonary vein isolation will be compared between the two groups. In addition, fluoroscopic time, procedure time, and complication rates for the high power ablation group will be compared with those with conventional power.

Ablation Index guided high power ablation will be performed in 70 patients with atrial fibrillation with prospectively and consecutively. A contact force-sensing catheter will be used. Ablation will be performed with point-by-point technique using Visitag automated annotation criteria as below;

Ablation Index(AI) target:

• Anterior/roof : 450 AI
• Anterior near carina area : 500 AI
• Posterior/inferior/carina : 350 AI
• Posterior near carina area : 400 AI
• Area near esophagus :25W, 15sec or 300 AI (no further ablation if esophageal temperature increase more than 39°C)
• Interlesion distance ≤ 4.5mm

VISITAGTM settings

• 2.5mm stability range
• 7 sec stability time
• FOT 25%, 3g force
• Tag size 2mm

Ablation parameters are preset as below;

• RF power range: 40W at anterior/roof, 30W at posterior/inferior, 25W at near esophagus area (decrease power 5W by operator decision)
• Target contact force range: 10-20 g
• Flow rate:
• 8 ml/min for STSF < 30W
• 15 ml/min for STSF ≥ 30W

Acute reconnection will be analysed according to predefined segments.

Subgroup analysis will be performed according to type of AF. Data of patients with paroxysmal atrial fibrillation and persistent atrial fibrillation will be analysed separately, and investigate whether this new ablation strategy is effective in both group of patients. To compare outcomes with OPITMUM phase 2 study, the proportion of patients with paroxysmal and persistent atrial fibrillation would be 75% and 25%. Therefore, 53 patients with paroxysmal atrial fibrillation and 17 patients with persistent atrial fibrillation will be enrolled in this study.

Inclusion Criteria:

• Patients with symptomatic paroxysmal or persistent AF who failed anti-arrhythmic agents

Exclusion Criteria:

• Patients who had previous ablation for AF
• Patients with left atrial diameter more than 50 mm
• Inability or unwillingness to receive oral anticoagulation with a vitamin K antagonist (VKA) or non-VKA (NOAC) agent
• Known severe left ventricular systolic dysfunction (ejection fraction <35%)
• Pregnancy