Clinical, morphological and molecular biological examination of the myocardium in COVID-19 patients

The presence of coronavirus-associated myocarditis remains controversial despite elevations in cardiac troponin and natriuretic peptide in many patients.Aim. To assess the morphological changes in the myocardium of patients who died due to coronavirus disease 2019 (COVID-19) and compare them with the intravital level of cardiac biomarkers.Material and methods. A total of 420 hospital charts and 77 autopsies of those who died from COVID-19 were analyzed. In 15 of 77 cases (19%) with histologically suspected myocarditis, an immunohistochemical examination of the myocardium with antibodies to CD3, CD45, CD8, CD68, CD34, Ang1, VWF, VEGF, HLA-DR, MHC1, C1q, VP1 of enteroviruses was performed, and in 8 patients with immunohistochemically confirmed myocarditis (10%) — polymerase chain reaction for SARS-CoV-2.Results. Hemorrhage, intramural thrombosis, necrosis of non-coronary origin, myocardial infarction and lymphocytic myocarditis were detected in 43%, 10%, 17%, 19% and 10% of cases, respectively, without coronavirus N and E gene sequences in the myocardium. Dysplasia, hyperplasia and hypertrophy of the vascular endothelium, expression of Ang1, VWF, VEGF, MHC1, C1q, VP1 of enteroviruses were determined in 100, 100, 87, 100, 75 and 62% of cases of myocarditis, respectively. There were no significant correlations between inflammatory biomarkers and myocarditis.Conclusion. The main morphological manifestation of COVID-19 in the myocardium is the so-called endotheliitis with dysplasia and endothelial activation, leading to hemorrhages, intramural thrombosis and necrosis. There is no convincing evidence of a direct involvement of coronavirus in myocarditis induction.