Abstract 21007: Role of Thick Fibrotic Tissue in the Left Atrium on the Outcome of Atrial Fibrillation Ablation

Introduction: Left Atrial (LA) Fibrosis may serve as a substrate for Atrial Fibrillation (AF) and the total percentage of LA fibrosis affects the outcome of ablation therapy. But the role of “thick” (transmural or near transmural) fibrotic tissue, as opposed to superficial fibrosis, in the AF prognosis is not well studied. We assess the amount of LA wall fibrosis thickness on AF ablation outcome. Methods and Results: Patients’ parameters were obtained from DECAAF trial. LA fibrosis was quantified with Late Gadolinium Enhancement MRI (LGE-MRI) and when within LA myocardium, 3 or more voxels (each voxel = 0.625mm) were enhanced that area was considered as thick fibrotic tissue. First Cox regression was devised to measure the impact of thick fibrosis on the outcome of AF ablation. Then patients were divided into 2 groups: First group with more than 3.89% of thick LA fibrosis and the second group with less than that. This cut-off was achieved through Receiver Operation Curve analysis of our cohort. Patients were 58.9 ± 10.9 of age and their amount of thick LA fibrosis was 3.5% ± 2.4%. The result of Cox regression showed: 1% increase in the extent of thick LA fibrosis, the recurrence rate of AF increases by 20% after ablation. (HR = 1.2, CI 95% = 1.1 - 1.3, P < 0.0001). The first and second group matched in terms of age, gender, LA volume, and co-morbidities. The first group were 2.9 times more at risk for AF recurrence after the ablation (CI95% = 1.9 - 4.5, P < 0.001) and they had a significantly lower chance of remaining AF free after ablation (0.385 vs 0.621, P < 0.0001) Conclusions: We found the percentage of LA wall fibrosis thickness to correlate with a worse AF ablation outcome and an increased risk of AF recurrence. Therefore assessing percentage of thick fibrotic tissue within LA wall may be of a greater interest than assessing total percentage of fibrosis.