Thromboembolic involvement and its possible pathogenesis in COVID-19 mortality: lesson from post-mortem reports

The emergence of Coronavirus Disease 19 (COVID-19) as a pandemic has claimed hundreds of thousands of lives worldwide since its initial breakout. With increasing reports from clinical observations and autopsy findings, it became clear that the disease causes acute respiratory distress syndrome (ARDS), as well as a broad spectrum of systemic and multiorgan pathologies, including angiopathy, endothelialitis, and thrombosis. Coagulopathy is associated with the activity of megakaryocytes, which play crucial roles in modulating the platelet homeostasis. Only a few autopsy reports include findings on thrombosis formation and the presence of megakaryocytes. Here we review and summarize the possible involvement and the pathophysiology of the thromboembolic events in COVID-19 patients based on post-mortem reports. We reviewed post-mortem reports from March 2020 to September 2020. Eleven autopsy reports that demonstrated thromboembolic involvement findings, either macroscopically or microscopically, were included in this review. All studies reported similar pulmonary gross findings. Not all studies described thrombi formation and megakaryocyte findings. Pulmonary embolism, coagulopathy, severe endothelial injury, and widespread thrombosis are frequent in COVID-19 patients, following many patients with high-level D-Dimer, increased fibrinogen, abnormal prothrombic coagulation, and thrombocytopenia. Reports showed that thrombus was also found in the lower extremities' deep veins and the prostatic venous plexus. In conclusion, a complex interaction of SARS-CoV-2 virus invasion with platelets, leukocytes, endothelial cells, inflammation, immune response, and the possible involvement of megakaryocytes may increase the cumulative risk of thrombosis by a yet unclear cellular and humoral interaction.