REN and cardiac arrhythmia: The renin–angiotensin system (RAS) is involved in the genesis of arrhythmia by the following two mechanisms: the induction of atrial fibrosis and structural remodeling by mitogen‐activated protein kinase (MAPK) expression and a reduction of collagenase activity, and the induction of electrical remodeling by a shortening of the atrial effective refractory period (AERP) and the action potential duration.11