There is a diverse spectrum of cardiovascular manifestations, ranging from limited necrosis of heart cells (causing injury), to myocarditis, to cardiogenic shock (an often fatal inability to pump sufficient blood). Cardiac injury, as reflected by concentrations of troponin (a cardiac muscle–specific enzyme) in the blood, is common with COVID-19, occurring in at least one in five hospitalized patients and more than half of those with preexisting heart conditions. Such myocardial injury is a risk factor for in-hospital mortality, and troponin concentration correlates with risk of mortality. Furthermore, patients with higher troponin amounts have markers of increased inflammation [including C-reactive protein, interleukin-6 (IL-6), ferritin, lactate dehydrogenase (LDH), and high neutrophil count] and heart dysfunction (amino-terminal pro-B–type natriuretic peptide) (9).
More worrisome than the pattern of limited injury is myocarditis: diffuse inflammation of the heart, usually representing a variable admixture of injury and the inflammatory response to the injury that can extend throughout the three layers of the human heart to the pericardium (which surrounds the heart). Unlike SARS-associated myocarditis, which did not exhibit lymphocyte infiltration, this immune and inflammatory response is a typical finding at autopsy after SARS-CoV-2 infections. Involvement of myocytes, which orchestrate electrical conduction, can result in conduction block and malignant ventricular arrhythmias, both of which can lead to cardiac arrest.
Along with such in-hospital arrythmias, there have been reports of increased out-of-hospital cardiac arrest and sudden death in multiple geographic regions of high COVID-19 spread, such as the 77% increase in Lombardy, Italy, compared with the prior year (10). There have been many reports of myocarditis simulating a heart attack, owing to the cluster of chest pain symptoms, an abnormal electrocardiogram, and increased cardiac-specific enzymes in the blood, even in patients as young as a 16-year-old boy. When there is extensive and diffuse heart muscle damage, heart failure, acute cor pulmonale (right heart failure and possible pulmonary emboli), and cardiogenic shock can occur.
