Myocardial Injury in Post Mortem Biopsies of Patients with COVID-19

Background: Myocardial injury is significantly and independently associated with mortality in COVID-19 patients. However, the pathogenesis of myocardial injury in COVID-19 is still not clear, and cardiac involvement by SARS-CoV-2 remains a major challenge worldwide.Aim: This histopathological and immunohistochemical study seeks to clarify the pathogenesis of myocardial injury in COVID-19.Methods: Postmortem minimally invasive autopsies were performed in two patients who died from COVID-19, and the myocardium samples were compared to a control patient. Immunohistochemistry (IHC) staining was performed using monoclonal antibodies against the following targets: caspase-1, ICAM-1, TNF-α, IL-4, IL-6, CD163, TGF-β, MMP-9, type 1 and type 3 collagen.Results: The histopathological analysis showed severe pericellular interstitial edema surrounding each of the cardiomyocytes. The IHC analysis showed increased expression of caspase-1, ICAM-1, IL-4, IL-6, CD163, MMP-9 and type 3 collagen in the COVID-19 patients compared to the control. On the other hand, no difference from the control was observed in expression of TNF-α, TGF-β and type 1 collagen. Conclusion: Our findings point to a pathogenesis related with pyroptosis leading to endothelial disfunction. The subsequent inflammation with associated interstitial edema could explain the myocardial disfunction and arrythmias in COVID-19 patients. The presence of Th2 response, MMP-9 and type-3 collagen suggests progression to myocardial fibrosis in the long term.