The Implications of Viral Particles in the Myocardium

Darryl Leong

Systolic left ventricular dysfunction in the absence of obstructive coronary artery disease has been described in several anecdotes and case reports in patients with COVID-19. The mechanisms underlying the cardiomyopathy is unclear. In a case report, Tavazzi, et al. describe the first instance of coronavirus-like particles seen by electron microscopy in the myocardium of a patient with COVID-19 who exhibited marked impairment in systolic left ventricular function1. These particles were seen within interstitial cytopathic macrophages and not within myocytes under electron microscopy of a single endomyocardial biopsy. In addition, only low-grade myocardial inflammation was observed, with no evidence of myocyte necrosis.

While this report is valuable in that it is the first to demonstrate likely SARS-CoV-2 localization within the heart, the authors prudently avoid ascribing a causal relationship between the viral particles and the left ventricular dysfunction. Previous research has shown that viral (e.g. parvovirus B19) genomes can be found in cardiac tissue in patients with no evidence of myocarditis2. Therefore, it remains unknown whether the localization of SARS-CoV-2 in cardiac tissue is simply the result of viremia or translocation of infected macrophages, or whether it has a direct pathogenic effect on the myocardium. Further evidence of a causal relationship, such as the demonstration of active myocarditis or histologic myonecrosis is needed to build the case that SARS-CoV-2 can directly cause myocardial damage. Numerous randomized, clinical trials of antiviral therapies in patients with COVID-19 are underway or being planned. If a reduction in adverse cardiac outcomes were shown in these trials, it would strengthen the evidence of a direct causal role of COVID-19 in left ventricular dysfunction.

1.           Tavazzi G, Pellegrini C, Maurelli M, Belliato M, Sciutti F, Bottazzi A, Sepe PA, Resasco T, Camporotondo R, Bruno R, Baldanti F, Paolucci S, Pelenghi S, Iotti GA, Mojoli F and Arbustini E. Myocardial localization of coronavirus in COVID-19 cardiogenic shock. Eur J Heart Fail. 2020.

2.           Kuhl U, Pauschinger M, Noutsias M, Seeberg B, Bock T, Lassner D, Poller W, Kandolf R and Schultheiss HP. High prevalence of viral genomes and multiple viral infections in the myocardium of adults with “idiopathic” left ventricular dysfunction. Circulation. 2005;111:887-93.

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