Differences in the structural characteristics and distribution of epicardial adipose tissue between left and right atrial fibrillation

Right atrial (RA) fibrillation (RAF) was previously characterized by initiation from RA ectopies, presence of a right-to-left dominant frequency gradient during atrial fibrillation (AF), and augmentation of the gradient by adenosine triphosphate infusion. We investigated structural characteristics of the bi-atria and epicardial adipose tissue (EAT) volume in patients with RAF. By using multidetector computed tomography, RA, left atrial (LA), right and LA appendage (RAA and LAA, respectively) volumes, pulmonary vein (PV) sizes, and EAT volumes were compared between the RAF group (n = 8) and LA fibrillation (LAF) group (n = 32). Compared with the LAF group, the LA volume was smaller (median 81.3 [95% CI, 74.2-88.5] vs. 64.5 [54.8-74.2] mL/m(2); P =0.04), the LAA volume was smaller (10.1 [9.0-11.3] vs. 6.5 [4.5-8.5] mL/m(2); italic toggle=P =0.008), and the RAA volume was larger (10.8 [9.1-12.4] vs. 14.1 [11.6-16.6] mL/m(2); P =0.044) in the RAF group. The RA volume was not significantly different between the groups (73.6 [66.8-80.3] vs. 68.1 [57.1-79.1] mL/m(2); P =0.47). The RAF group had smaller PVs (1.44 [1.33-1.55] vs. 1.12 [0.94-1.30] cm(2)/m(2) for the left inferior PV; P =0.01). Both the LA-EAT and RA-EAT volumes were smaller in the RAF group than the LAF group (4.2 [2.8-5.6] vs. 9.1 [7.8-10.4] mL/m(2); P < 0.001 and 5.3 [4.3-6.3] vs. 9.5 [8.4-10.6] mL/m(2); P < 0.001, respectively). RAF was structurally characterized by predominant RAA enlargement, small left atrium, and less EAT surrounding the atria. Electrical properties that determine the features of AF (RAF vs. LAF) may be genetically linked to structural properties.