REN and Myocardial fibrosis: Activation of the renin-angiotensin-aldosterone system (RAAS) is implicated in the myocardial remodeling in AS; raised myocardial angiotensin converting enzyme (ACE) concentrations are associated with AS and AR, which in turn is associated with increased collagen and fibronectin synthesis, leading to myocardial fibrosis [110].