COL1A1 and atrial fibrillation: After exposure to EAT secretome, COL1A1 and FN1 expression in human atrial fibroblasts were 3.7 and 4.7 times higher, respectively, in patients with versus without AF (p = 0.03, p = 0.02), (Fig. 1a, b, Additional file 1: Table S2).