It has been found that CTGF activates pro‐fibrotic signalling pathways such as those of Smad, ERK and WNT.31, 32 TGFβ1 regulates pro‐fibrotic effects by altering Smad protein and CTGF gene expression.28 CTGF overexpression is associated with atrial fibrosis in patients with chronic AF.33 AF with lowered LVEF is associated with AAR in the AF pig model, which is characterized by increased atrial fibrosis and collagen secretion. Here, TGFB1 is linked to atrial fibrillation.