Procedural efficiencies, lesion metrics, and 12-month clinical outcomes for Ablation Index-guided 50 W ablation for atrial fibrillation

Aims The safety of Ablation Index (AI)-guided 50 W ablation for atrial fibrillation (AF) remains uncertain, and mid-term clinical outcomes have not been described. The interplay between Al and its components at 50W has not been reported. Methods and results Eighty-eight consecutive AF patients (44% paroxysmal) underwent Al-guided 50W ablation. Procedural and 12-month clinical outcomes were compared with 93 consecutive controls (65% paroxysmal) who underwent Al- guided ablation using 35-40 W. Posterior wall isolation (PWI) was performed in 44 (50%) and 23 (25%) patients in the 50 and 35-40W groups, respectively, P< 0.001. The last 10 patients from each group underwent analysis of individual lesions (n = 1230) to explore relationships between different powers and the Al components. Pulmonary vein isolation was successful in all patients. Posterior wall isolation was successful in 41/44 (93.2%) and 22/23 (95.7%) in the 50 and 35-40W groups, respectively (P=0.685). Radiofrequency times (20 vs. 26 min, P< 0.001) and total procedure times (130 vs. 156 min, P= 0.002) were significantly lower in the 50W group. No complication or steam pop was seen in either group. Twelve-month freedom from arrhythmia was similar (80.2% vs. 82.8%, P=0.918). A higher proportion of lesions in the 50W group were associated with impedance drop >7 Omega (54.6% vs. 45.5%, P< 0.001). Excessive ablation (Al >600 anteriorly, >500 posteriorly) was more frequent in the 50 W group (9.7% vs. 4.3%, P< 0.001). Conclusion Ablation Index-guided 50 W AF ablation is as safe and effective as tower powers and results in reduced ablation and procedure times. Radiofrequency lesions are more likely to be therapeutic, but there is a higher risk of delivering excessive ablation.