Clinical implications of microvascular CT scan signs in COVID-19 patients requiring invasive mechanical ventilation

Abstract

Purpose: COVID-19-related acute respiratory distress syndrome (ARDS) is characterized by the presence of signs of microvascular involvement at the CT scan, such as the vascular tree in bud (TIB) and the vascular enlargement pattern (VEP). Recent evidence suggests that TIB could be associated with an increased duration of invasive mechanical ventilation (IMV) and intensive care unit (ICU) stay. The primary objective of this study was to evaluate whether microvascular involvement signs could have a prognostic significance concerning liberation from IMV.

Material and methods: All the COVID-19 patients requiring IMV admitted to 16 Italian ICUs and having a lung CT scan recorded within 3 days from intubation were enrolled in this secondary analysis. Radiologic, clinical and biochemical data were collected.

Results: A total of 139 patients affected by COVID-19 related ARDS were enrolled. After grouping based on TIB or VEP detection, we found no differences in terms of duration of IMV and mortality. Extension of VEP and TIB was significantly correlated with ground-glass opacities (GGOs) and crazy paving pattern extension. A parenchymal extent over 50% of GGO and crazy paving pattern was more frequently observed among non-survivors, while a VEP and TIB extent involving 3 or more lobes was significantly more frequent in non-responders to prone positioning.

Conclusions: The presence of early CT scan signs of microvascular involvement in COVID-19 patients does not appear to be associated with differences in duration of IMV and mortality. However, patients with a high extension of VEP and TIB may have a reduced oxygenation response to prone positioning.

Trial registration: NCT04411459.

Keywords: Acute respiratory distress syndrome; Mechanical ventilation; Novel coronavirus disease 2019; Pulmonary perfusion; Thoracic imaging.

Fig. 1

CT scans showing vascular enlargement pattern (VEP) and vascular tree-in-bud (TIB) in two patients with COVID-19 pneumonia. Notes: A—Bilateral peripheral areas of ground-glass opacification and crazy paving in the upper lobes. Dilated segmental and subsegmental vessels (VEP—arrowheads) are visible inside these areas. B—Targeted image shows striking dilatation of peripheral subpleural vessel in upper left lobe with a branching aspect resembling a budding tree (arrow). Please note that vascular TIB is visible only within the area of ground-glass-opacity in this picture

Fig. 2

Spearman heatmap regarding the extension of the radiologic signs explored. Abbreviations: VEP—vascular enlargement pattern; TIB—tree in bud sign; GGO—ground glass opacities. Notes—the values reported in the cells refer to the rho coefficient for the bivariate correlation of the two variables; p < 0.05; *p < 0.01

Fig. 3

Cumulative incidence functions of liberation from mechanical ventilation. Abbreviations: TIB—tree in bud; VEP—vascular enlargement pattern; MV—mechanical ventilation

Fig. 4

Prevalence of extended radiologic signs in different contexts. Abbreviations: VEP—vascular enlargement pattern; TIB—tree in bud; PN—peripheral nodules; GGO—ground glass opacities; CP—crazy paving; Cons—consolidations. Notes: Graphs show the prevalence of VEP, TIB and PN involving 3 or more lobes and GGO, CP and Cons extended for over the 50% of pulmonary parenchyma. *p < 0.05 at Chi-square test