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

Bulfamante, G. P.; Perrucci, G. L.; Falleni, M.; Sommariva, E.; Tosi, D.; Martinelli, C.; Songia, P.; Poggio, P.; Carugo, S.; Pompilio, G.

Background - Cardiovascular complication in patients affected by novel Coronavirus respiratory disease (COVID-19) are increasingly recognized. However, although a cardiac tropism of SARS-CoV-2 for inflammatory cells in autopsy heart samples of COVID-19 patients has been reported, the presence of the virus in cardiomyocytes has not been documented yet. Methods - We investigated for SARS-CoV-2 presence in heart tissue autopsies of 6 consecutive COVID-19 patients deceased for respiratory failure showing no signs of cardiac involvement and with no history of heart disease. Cardiac autopsy samples were 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. A variable pattern of cardiomyocytes injury was observed, spanning from the absence of cell death and subcellular alterations hallmarks to the 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 analysis of autopsy cases, the presence of SARS-CoV-2 into cardiomyocytes, determining variable patterns of intracellular involvement, has been documented. All these findings suggest the need of a cardiologic surveillance even in survived COVID-19 patients not displaying a cardiac phenotype, in order to monitor potential long-term cardiac sequelae.