Pathology and Pathogenesis of Cardiac Injury in COVID-19 Infections in Humans

Since Dec 2019, coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) has resulted in considerable morbidity and mortality throughout the world. On April 21 2020, Italy and US have registered over 187,000 and 855,000 cases of confirmed COVID-19 disease respectively, with one of the highest death rates in the world, which stands at more than 25,000 individuals in Italy and 47,000 in US. Epidemiologic modeling from multiple groups indicate the scope of the problem, with a potential for over 200,000 deaths in the U.S. alone, with large percentage of the population infected. Mortality from COVID-19 is associated with the presence of severe respiratory illness, although recent studies indicate 20%-30% of patients have evidence of COVID-19 associated cardiac injury defined as decline in ejection fraction or troponin I elevation (1,2). Anecdotal evidence suggests the presence of abnormal EKG findings compatible with myocardial ischemia but whether this is from epicardial coronary thrombosis, myocarditis, or microvascular thrombosis remains uncertain although all have been postulated (3). Regardless, patients with cardiac injury have higher mortality than those without, and sudden cardiac death has been described in some of these patients (1). Two thirds of patients with cardiovascular history were more likely to develop cardiac complications (4). Isolated reports have described fulminant myocarditis in the setting of high viral load with autopsy findings consistent with inflammatory mononuclear infiltrates (5). However, no systematic autopsy studies of patients dying from COVID-19 have ever been conducted. The Papa Giovanni XXIII Hospital, Bergamo had treated about 2000 patients with COVID-19 and performed systematic cardiac autopsies from a series of 60 patients who died or presented with/without a picture of cardiac injury and were COVID-19 positive. Detailed clinical data on all these patients are available.

Background Much about the pathogenesis of SARS-CoV-2 and the heart remains unknown. Angiotensin (AT) converting enzyme 2 (ACE2) is known as the cellular receptor for both SARS-CoV and SARS-CoV-2 but also as an endogenous counter- regulator of the renin-angiotensin system (RAS). ACE2 is ubiquitously expressed with the highest levels detected in the cardiovascular system (cardiomyocytes, cardiac fibroblasts, vascular smooth muscle cells and endothelial cells) as well as gut, kidneys and lungs. In general, loss of ACE2 increases susceptibility to cardiovascular disease such as myocardial infarction and hypertension while gain of function ACE2 has shown protective roles in various models of cardiovascular disease (6). The bifunctional role of ACE2 as a receptor for SARS-COV-2 but also as a protective factor against cardiovascular disease means careful understanding of the role of ACE2 during SARS-CoV-2 is needed. In this proposal investigators will examine cardiac tissues from patients dying of COVID-19 and examine the effect of infection on the expression of ACE2 on various cardiac cells. Investigators will also evaluate and validate this hypothesized mechanism of viral entry by ACE2 and trans-membrane serine protease which promotes entry of SARS-COV-2 into cells through a separate mechanisms.

Study Aims:

1. Describe the cardiac pathological findings from series of 60 patients dying from COVID-19 using cardiac samples sent to CVPath Institution from Papa Giovanni XXIII Hospital, Bergamo, Italy to study the correlations between clinical risk factors and myocardial findings and difference from other viral myocarditis;
2. Understand the relationship between viral load in cardiac tissues and the extent of damage seen on myocardial histological sections; and
3. Co-localize the SARS-CoV-2 using RNAscope in situ hybridization, with its entry receptor ACE2 and serine protease TMPRSS2 (type II transmembrane serine protease) in different cell types found in the heart, such as endothelial, smooth muscle, myocardial, fibroblastic and inflammatory cells, to better understand the pathogenesis of the disease.

Methods: