Pulmonary vascular endothelial injury and acute pulmonary hypertension caused by COVID-19: the fundamental cause of refractory hypoxemia?

Coronavirus disease (COVID-19) is a severe infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that binds to the cells; angiotensin converting enzyme 2 (ACE2) receptor. In the first severe case of COVID-19 in Shenzhen city, we found that in addition to the typical clinical manifestations, our patient presented hemoptysis, refractory hypoxemia and pulmonary fibrosis-like changes on computed tomography (CT) involving alveoli and pulmonary interstitium in the early stage and acute pulmonary hypertension and right heart failure in the later stage, which were not completely justified by myocarditis, acute respiratory distress syndrome (ARDS), pulmonary fibrosis and high PEEP level. The lung compliance deterioration of this patient was not as serious as we expected, indicating classic ARDS was not existed. Simultaneously, the first autopsy report of COVID-19 in China showed normal-structured alveoli and massive thick excretion in the airway. Then, we speculated that the virus not only attacked alveolar epithelial cells, but also affected pulmonary vascular endothelial cells. Imbalance in the ACE2-RAAS- bradykinin axis and the cytokine storm could be an important mechanism leading to pathophysiological changes in pulmonary vascular and secondary refractory hypoxemia. Pulmonary vasculitis or capillaritis associated to immune damage and an inflammatory storm could exist in COVID-19 because of ground-glass opacities in the subpleural area, which are similar to connective tissue disease associated interstitial lung disease (CTD-ILD). Thus, this case elucidates new treatment measures for COVID-19.

Keywords: ACE2; coronavirus disease (COVID-19); pulmonary hypertension; pulmonary vascular endothelium; refractory hypoxemia.