TGFB1 and atrial fibrillation: Fibrosis is a complex process resulting from activation of select signalling pathways, such as TGF‐β1 signalling.11 TGF‐β1 is essential for the development of atrial fibrosis.12, 13, 14 The levels of TGF‐β1 are increased in the plasma and atria of AF patients.15, 16 Moreover, animal models have revealed that transgenic overexpression of TGF‐β1 results in atrial‐specific fibrosis and increases AF susceptibility.17, 18, 19 Thus, we used TGF‐β1‐induced CFs to establish an in vitro model of atrial fibrosis.