Abstract 10850: Epicardial Adipose Tissue is Associated With Left Atrial Volume and Fibrosis in Patients With Atrial Fibrillation

Background : Obesity is a risk factor for atrial fibrillation (AF) and strongly influences response to treatment. Atrial fibrosis shows similar associations. Epicardial adipose tissue (EAT) may be a link between these associations. We sought to assess whether EAT is associated with body mass index (BMI), left atrial (LA) volume and fibrosis. Methods: LA fibrosis and EAT were assessed using Late Gadolinium Enhancement, and Dixon MRI sequences, respectively. We derived 3D models incorporating fibrosis and EAT to assess spatial colocalization: we measured the distance of fibrotic and non-fibrotic areas to the nearest EAT, and calculated the volume of EAT within a radius of 5 mm for every LA surface point. Results: 103 AF patients (64% paroxysmal, 73% male) were analyzed. LA volume index was 54.9 [41.2, 69.7] mL/m 2 , LA EAT index was 17.4 [12.7, 22.9] mL/m 2 , and LA fibrosis was 17.1 [12.4, 23.1] %. LA EAT was significantly correlated with BMI (R=0.557, p<0.001); as well as with LA volume and LA fibrosis after BSA adjustment (R=0.579 and R=0.432 respectively, p<0.001 for both) (Panel A). Multivariable analysis showed LA EAT to be independently associated with LA volume and fibrosis. Aggregation of local EAT proximity values in all models revealed that the minimum distance to fat was significantly greater for fibrotic LA surface regions compared to non-fibrotic areas (6.97 mm [3.28, 12.13] vs 5.71 mm [2.58, 10.35], p<0.001) (Panel C). The proportion of LA surface points having fat within a radius of 5 mm was greater for non-fibrotic compared to fibrotic regions (37.6% [23.4, 48] vs 41.6% [31.2, 58.1] respectively, p=0.021). Thus, 3D registration of fat and fibrosis around the LA showed no clear spatial overlap between EAT and fibrotic LA regions (Panel B). Conclusion: LA EAT is associated with obesity (BMI) as well as LA volume and fibrosis. Regions of LA EAT are not colocalized with fibrotic areas, suggesting a systemic or paracrine mechanism rather than EAT infiltration of fibrotic areas.