TGFB1 and atrial fibrillation: Secreted CTGF, in turn, attracted fibroblasts in the outer AF to the disrupted area for repair.23 In addition, secreted CTGF in a local microenvironment could directly bind TGF‐β and enhance TGF‐β binding to its receptors;40 therefore, a high level of CTGF could be maintained even in the presence of a low level of TGF‐β.