The role of angiotensin-converting enzyme 2
Angiotensin-converting enzyme 2 (ACE2) converts angiotensin I (Ang I) and angiotensin II (Ang II) into the biologically active peptide Ang-(1-9) and Ang-(1-7), respectively.10,11This provides counter-regulatory effects of ACE in the renin-angiotensin-aldosterone system (RAAS). ACE2 could be a functional receptor and cellular entry point for SARS-CoV-2 and SARS-CoV to invade target cells in heart, lung, and kidney where prominent expressions of ACE2 are observed.12,13Although the current evidence remains insufficient, SARS-CoV-2 might cause direct injury of myocardium by binding to ACE2.14 Previous data from SARS-CoV might provide some theoretical mechanism for COVID-19 because SARS-CoV and SARS-CoV-2 have similar affinity to ACE2.12,13 The downregulation of myocardial ACE2 expressions after SARS-CoV infection leads to excessive accumulation of Ang II and causes myocardial injury, remodeling and even adverse cardiac outcomes.15 This might underlie AF arrhythmogenesis in COVID-19. Atrial ACE2 expressions would decrease the levels of transforming growth factor-β1(TGF-β1) and collagen deposition.16ACE2 might be able to regulate cardiac action potential.17Laboratory data also demonstrated that ACE2 metabolites, Ang-(1-7), could modulate electrophysiological characteristics and calcium hemostasis in atrial tissue and pulmonary vein cardiomyocytes.18,19The downregulation of ACE2 in COVID-19 might increase AF vulnerability and its perpetuation.