ACE2 and atrial fibrillation: SARS-CoV-2 uses ACE2 receptors to enter host cells, including type 2 pneumocytes, cardiomyocytes, pericytes, macrophages, and endothelial cells. ACE2 also plays an important role in angiotensin II regulation and protects against the detrimental effect of the renin–angiotensin–aldosterone system (RAAS) on the cardiovascular system [19]. RAAS has an important role in the development of AF.