1362Prospective use of ablation index targets improves clinical outcomes following ablation for atrial fibrillation

Background: Despite use of contact force (CF)-sensing catheters for PVI, atrial tachyarrhythmia (AT) recurrence due to late pulmonary vein reconnection (PVR) is still common. Ablation Index (AI) is a novel ablation quality marker that incorporates CF, time and power in a weighted formula. We hypothesised that prospective use of our previously-published derived AI ablation targets would result in better acute and late outcomes when compared to CF-guided ablation. Methods: 89 consecutive patients (44 paroxysmal AF) underwent AI-guided PVI for symptomatic drug-refractory AF. AI targets for each lesion were 550 for anterior wall/roof and 400 for posterior/inferior walls. Procedural and clinical outcomes of these patients were compared to 89 propensity-matched controls who underwent CF-guided PVI. All 178 procedures were otherwise identical in use of Carto, VisiTag, point-by-point ablation, non-steerable sheath, and systematic Adenosine to unmask PVR. In each group, 25 patients underwent detailed analysis of all VisiTags (N=4018) for ablation duration, CF, FTI and impedance drop. Results: Patient demographics and follow-up duration (median 12 months) were not different between groups. No major complications occurred in any patient in either group. First-pass isolation was more frequent in AI group than CF group (173 (97%) vs 149 (84%) circles, P<0.001), and acute PVR was lower (10 (11%) vs 24 (27%) patients, P=0.008). Ablation time was lower in AI group (48±10 min vs 53±13, P=0.03). The median impedance drop for AI group was significantly higher than in CF group (13.7 Ω (IQR 9-19) vs 8.8 (5.2-13), P<0.001), as was the median CF (11g (8-17) vs 9.3 (7-13.3), P<0.001). After adjustment for CF using multivariable linear regression, AI group membership was still associated with significantly higher impedance drop (P<0.001). Over the follow-up period, AT recurrence was significantly lower in AI group (19/89 (21%)) than in CF group (32/89 (36%)), P=0.03). Conclusion: AI-guided ablation is associated with significant improvements in the incidence of acute PVR and in the rate of AT recurrence during follow-up as compared to CF-guided ablation. Impedance drop data suggest that improved results are due to creation of higher quality lesions with lower ablation times. Abstract 1362 Figure.