Furthermore, Ang II produces transforming growth factor-β1 (TGF-β1), one of the key downstream efforts of Ang II that are secreted from cardiomyocytes and fibroblasts, which is a major factor in promoting fibrosis through the TGF-β1/Smad pathway to mediate the downstream gene product and connective tissue growth factor (CTGF), to increase atrial fibrosis and conduction abnormalities, and to promote AF. Here, TGFB1 is linked to atrial fibrillation.