REN and atrial fibrillation: Various animal model studies of AF reiterated that the activation of the renin–angiotensin–aldosterone system (RAAS) leads to fibrosis and myocardial structural remodeling and demonstrated the cardioprotective effects of angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs) and anti-inflammatory drugs with antioxidant properties [9, 10].