TGFB1 and atrial fibrillation: AF-related alteration of atrial structure starts with the differentiation of cardiac fibroblasts into myofibroblasts, which is regulated by numerous triggers, including angiotensin-II, noradrenaline, thyroid hormones, inflammatory cytokines, chemokines, matrix metalloproteinases, galectine-3, soluble suppression of tumorigenesis-2 (sST2), TGF-beta-1 and microRNAs (Figure 2).