Left atrial anterior line ablation using ablation index and inter-lesion distance measurement

Background: Ablation index (AI) is a novel ablation quality marker that incorporates contact force (CF), time and power in a weighted formula to provide accurate information about lesion formation during catheter ablation. This index has been evaluated for pulmonary vein isolation (PVI) but has not been systematically used for other left atrial (LA) procedures so far. The aim of this study is to evaluate the feasibility and efficacy of this index for LA anterior line (AL) ablation (LAALA). Methods: 30 consecutive patients with persistent atrial fibrillation or LA macro-reentrant tachycardia and large low-voltage area at the left atrial anterior wall were evaluated and divided into 2 groups: group 1 (15 pts) LAALA guided by CF; group 2 (15 pts) LAALA guided by AI target (500) and inter-lesion distance ≤ 6 mm. Results: In group 2, shorter ablation time (12.5 ± 3.8 vs 17 ± 7 min, p = 0.049), overall RF application time (7.9 ± 1.4 vs 10.8 ± 3.2 min. p = 0.01) and less radiofrequency (RF) applications (14.5 ± 2.3 vs 20.5 ± 6.1 p = 0.01) were necessary to achieve AL bi-directional block. Acute reconnection of the AL was documented in three patients (20%) of group 1 and in no patient of group 2 (20% vs 0% p = 0.22). At site of reconnection, an inter-lesion distance > 6 mm was always found. There was no difference in terms of CF and power between group 2 and group 1. AI was statistically different between group 2 and group 1 (AI = 511 ± 77 vs 451 ± 111; p = 0.004). Conclusion: AI-guided LAALA in this study was feasible and featured by shorter ablation time, shorter overall RF application time and a reduced number of RF applications to achieve AL bidirectional block.