Microvascular Injury With Secondary Edema, Bronchoconstriction and Vasoconstriction of Non-involved Lung Parenchymal Segments May Contribute to Clinical Deterioration of Non-critically Ill Patients Hospitalized for SARS-CoV-2 Pneumonia Without Evidence of Pulmonary Embolism: A Preliminary Study.

Purpose: We aimed to better understand the pathophysiology of SARS-CoV-2 pneumonia in non-critically ill hospitalized patients secondarily presenting with clinical deterioration and increase in oxygen requirement.Methods: We consecutively enrolled patients without clinical or biological evidence for superinfection, without left ventricular (LV) dysfunction and for whom a pulmonary embolism was discarded by computed tomography pulmonary angiography. We investigated lung ventilation and perfusion (LVP) by LVP scintigraphy, and, 24 hours later, left and right ventricular function by 99mTc-labelled albumin gated-blood-pool scintigraphy with late (60 mn) tomographic albumin images on the lungs to evaluate lung albumin retention that could indicate microvascular injuries with secondary edema. Results: We included 13 patients with confirmed SARS-CoV-2 pneumonia. All had CT evidence of organizing pneumonia and normal LV ejection fraction.No patient demonstrated preserved ventilation with perfusion defect (mismatch), which may eliminate a distal lung thrombosis. Patterns of ventilation and perfusion were heterogeneous with sometimes healthy lung segments paradoxically hypoperfused and hypoventilated while both normal perfusion and ventilation were maintained in segments with organizing pneumonia (n=4). Lung albumin retention in area of organizing pneumonia was observed in 9 patients, indicating microvascular injuries, vessel permeability increase and secondary edema.Conclusion: In hospitalized non-critically ill patients without pulmonary embolism or LV dysfunction, various types of damage may contribute to clinical deterioration including microvascular injuries and secondary edema, broncho and vasoconstriction of area not involved by organizing pneumonia while no evidence was found for significant distal thrombosis detectable by LVP scintigraphy.