Evidence of SARS-CoV-2 transcriptional activity in cardiomyocytes of covid-19 patients without clinical signs of cardiac involvement

Aims: A considerable proportion of patients affected by coronavirus respiratory disease (COVID-19) develop cardiac injury. The viral impact in cardiomyocytes deserves, however, further investigations, especially in asymptomatic patients. Methods: We investigated for SARS-CoV-2 presence and activity in heart tissues of six consecutive COVID-19 patients deceased from respiratory failure showing no signs of cardiac involvement and with no history of heart disease. Cardiac autopsy samples were collected within 2 h after death, and then analysed by digital PCR, Western blot, immunohistochemistry, immunofluorescence, RNAScope, and transmission electron microscopy assays. Results: The presence of SARS-CoV-2 into cardiomyocytes was invariably detected in all assays. A variable pattern of cardiomyocyte injury was observed, spanning from absence of cell death and subcellular alterations hallmarks, to intracellular oedema and sarcomere ruptures. In addition, we found active viral transcription in cardiomyocytes, by detecting both sense and antisense SARS-CoV-2 spike RNA. Conclusions: In this autopsy analysis of patients with no clinical signs of cardiac involvement, the presence of SARS-CoV-2 in cardiomyocytes has been detected, determining variable patterns of intracellular damage. These findings suggest the need for cardiologic surveillance in surviving COVID-19 patients not displaying a cardiac phenotype.