key: cord-0769531-hbn69kmi
authors: Lang, Min; Som, Avik; Mendoza, Dexter P; Flores, Efren J; Reid, Nicholas; Carey, Denston; Li, Matthew D; Witkin, Alison; Rodriguez-Lopez, Josanna M; Shepard, Jo-Anne O; Little, Brent P
title: Hypoxaemia related to COVID-19: vascular and perfusion abnormalities on dual-energy CT
date: 2020-04-30
journal: Lancet Infect Dis
DOI: 10.1016/s1473-3099(20)30367-4
sha: 35fec4b853d39be591c0b5cf3444fe621fcb4ffc
doc_id: 769531
cord_uid: hbn69kmi

nan

in any of the studies, and segmental increased perfusion to areas of infarction would be very atypical. Furthermore, a peripheral halo of increased perfusion has not been described in pulmonary infarction, but has been described once pre viously in a case of bacterial pneu monia. 5 However, blood and sputum cultures were negative in the three patients with COVID19 at our hospital and did not suggest bacterial coinfection. It might be possible that the inflammatory response to COVID19 resembles more of a bacterial infection than a viral infection. Overall, the combination of these imaging findings is novel for COVID19 pneumonia.

Treatment for acute respiratory failure in patients with COVID19 is challenging in part because of little understanding of the underlying pathophysiology. Our findings are atypical for acute respiratory distress syndrome or thrombotic vascular disease and point to a possible central role for previously underappreciated pulmonary vascular shunting. More detailed assessments of vascular and perfusion changes in patients with COVID19 are urgently needed.

BPL reports royalties from Elsevier as a textbook author and editor, outside the submitted work. AW reports personal fees from Bayer Pharmaceuticals, outside the submitted work. All other authors declare no competing interests.

Studies have shown that some patients with coronavirus disease 2019 (COVID19) and acute hypoxaemic respiratory failure have preserved lung compliance, suggesting that processes other than alveolar damage might be involved in hypoxaemia related to COVID19 pneumonia. 1 The typical imaging features of COVID19 pneumonia, including peripheral groundglass opacities with or without consolidation, are also non specific and can be seen in many other diseases. 2 There has been increasing attention on microvascular thrombi as a possible explanation for the severe hypoxaemia related to COVID19. 3, 4 Dualenergy CT imaging can be used to characterise lung perfusion and is done as part of the standard protocol for imaging pulmonary embolism at our institution. Three patients with COVID19, as confirmed by nasopharyngeal RTPCR at our hospital, who did not have a history of smoking, asthma, chronic obstructive pulmonary disease, or other pulmonary conditions, underwent dualenergy CT imaging for elevated concentrations of Ddimer (>1000 ng/mL) and clinical suspicion of pulmonary emboli. Although no pulmonary emboli were observed in these individuals, we noted striking perfusion abnormalities that have not been previously described; in retrospect, at least nine other COVID19 cases also shared these findings. In addition to the typical CT features of COVID19 pneumonia, 2 we observed considerable proximal and distal pulmonary vessel dilatation and tortuosity, predominately within, or surrounding, areas of lung opacities. Here, we present the first published images from dualenergy CT imaging of COVID19 pneumonia that show profound vascular and perfusion abnormalities (figure; appendix).

Three major findings from dual energy CT were observed on the images of pulmonary blood volume perfusion: preferentially increased perfusion of the lungs proximal to areas of lung opacity, decreased areas of peripheral perfusion corresponding to peripheral lung opacities, and a halo of increased perfusion surrounding peripheral areas of consolidation. The observed pulmonary vascular dilation might be due to relative failure of normal, physiological hypoxic pulmonary vasoconstriction in the setting of overactivation of a regional vasodilatation cascade as part of a dysfunctional and diffuse inflammatory process. Additionally, the mosaic perfusion pattern did not correspond to findings of bronchial wall thickening or secretions, making airway disease as the main underlying cause of hypoxaemia unlikely. Therefore, these perfusion abnormalities, combined with the pulmonary vascular dilation we observed, are suggestive of intrapulmonary shunting toward areas where gas exchange is impaired, resulting in a worsening ventilation-perfusion mismatch and clinical hypoxia. Although peripheral opacities with hypoperfusion can be seen in pulmonary infarction, no pulmonary emboli were observed

Clinical course and risk factors for mortality of adult inpatients with COVID19 in Wuhan, China: a retrospective cohort study

Dualenergy CT: spectrum of thoracic abnormalities

Chest CT findings in coronavirus disease19 (COVID19): relationship to duration of infection

Incidence of thrombotic complications in critically ill ICU patients with COVID19