Pulmonary arterial thrombosis in Covid-19 with fatal outcome: results from a prospective, single-center, clinicopathologic case series

This autopsy study correlated pathologic and clinical findings of 11 deceased patients (age 66 to 91 years) who were randomly selected from a group of 48 deceased with Covid-19. As main finding, thrombotic material was found in branches of the pulmonary arteries involving vessels of all size (at a macroscopic as well as at a microscopic level). Further, bilateral diffuse alveolar damage, characterized by edema, hyaline membranes and proliferation of pneumocytes and fibroblasts, was a major finding in deceased Covid-19 patients.

Another recent autopsy study of 12 Covid-19 positive deaths (1 )also reported a remarkably high incidence of thromboembolic events and found pulmonary embolism as cause of death in one third of investigated cases.

The underlying mechanisms of these observations are not completely clear, so far. Covid-19 potentially provokes Covid-19-associated coagulopathy (CAC), which promotes microangiopathy and disseminated intravascular coagulation, finally resulting in widespread microvascular thrombosis. Moreover, diffuse alveolar damage is supposed to contribute to pulmonary arterial thrombosis. In addition, ACE-2 receptor mediated infection of endothelial cells seems to result in endothelial damage. The combination of alveolar and vascular alterations might explain the rapid clinical deterioration, which is observed in most severe cases of Covid-19. Recently, the term MicroCLOTS (Microvascular COVID-19 lung vessel obstructive thromboinflammatory syndrome) has been introduced for characterization of a progressive thromboinflammatory syndrome in Covid-19 (2)

Regarding treatment options, recent data suggest a reduction in mortality upon anticoagulation treatment (3) Interestingly, the patients assessed by Lax SF et al. developed thrombosis despite prophylactic anticoagulation treatment. This study underlines the need for prospective studies assessing different anticoagulation regimes and intensities in patients with Covid-19. Further, it remains to be clarified, how anticoagulation needs to be adapted to different settings in the Covid-19 pandemic, differing between critically ill patients, stable hospitalized patients and outpatients with Covid-19.