Phenotypic heterogeneity of COVID-19 pneumonia: clinical and pathophysiological relevance of the vascular phenotype.

Recent data support the existence of a distinctive 'vascular' phenotype with the involvement of both pulmonary parenchyma and its circulation in COVID-19 pneumonia. Its prompt identification is important for the accurate management of COVID-19 patients. The aim is to analyse the pro and contra of the different modalities to identify the 'vascular' phenotype. Chest computed tomography scan and angiogram may quantify both parenchyma and vascular damage, but the presence of thrombosis of pulmonary microcirculation may be missed. Increased d-dimer concentration confirms a thrombotic state, but it cannot localize the thrombus. An elevation of troponin concentration non-specifically reflects cardiac injury. Echocardiogram and electrocardiogram provide specific signs of right ventricular pressure overload. This is particularly relevant for the 'vascular' phenotype, which does not necessarily represent the result of thrombo-embolic venous complications, but more frequently, it is the result of pulmonary microcirculation thrombosis in situ and needs immediate therapeutic action. CONDENSED ABSTRACT: Despite diagnosis of the 'vascular' phenotype of COVID-19 pneumonia may be subtle, the evidence indicates a reasonable possibility of identifying it already in the initial stage of the infection. Chest computed tomography scan and angiogram, increased d-dimer concentration, and elevation of troponin concentration may be not sufficient to identify 'vascular' phenotype. Echocardiogram and electrocardiogram provide specific signs of right ventricular pressure overload. This is particularly relevant for the 'vascular' phenotype, which does not necessarily represent the result of thrombo-embolic venous complications, but more frequently, it is the result of pulmonary microcirculation thrombosis in situ and needs immediate therapeutic action.