Acute Pulmonary Embolism in COVID-19: A Potential Connection between Venous Congestion and Thrombus Distribution

Abstract

Background: Vascular abnormalities, including venous congestion (VC) and pulmonary embolism (PE), have been recognized as frequent COVID-19 imaging patterns and proposed as severity markers. However, the underlying pathophysiological mechanisms remain unclear. In this study, we aimed to characterize the relationship between VC, PE distribution, and alveolar opacities (AO). Methods: This multicenter observational registry (clinicaltrials.gov identifier NCT04824313) included 268 patients diagnosed with SARS-CoV-2 infection and subjected to contrast-enhanced CT between March and June 2020. Acute PE was diagnosed in 61 (22.8%) patients, including 17 females (27.9%), at a mean age of 61.7 ± 14.2 years. Demographic, laboratory, and outcome data were retrieved. We analyzed CT images at the segmental level regarding VC (qualitatively and quantitatively [diameter]), AO (semi-quantitatively as absent, <50%, or >50% involvement), clot location, and distribution related to VC and AO. Segments with vs. without PE were compared. Results: Out of 411 emboli, 82 (20%) were lobar or more proximal and 329 (80%) were segmental or subsegmental. Venous diameters were significantly higher in segments with AO (p = 0.031), unlike arteries (p = 0.138). At the segmental level, 77% of emboli were associated with VC. Overall, PE occurred in 28.2% of segments with AO vs. 21.8% without (p = 0.047). In the absence of VC, however, AO did not affect PE rates (p = 0.94). Conclusions: Vascular changes predominantly affected veins, and most PEs were located in segments with VC. In the absence of VC, AOs were not associated with the PE rate. VC might result from increased flow supported by the hypothesis of pulmonary arteriovenous anastomosis dysregulation as a relevant contributing factor.

Impact of COVID-19 pneumonia on pulmonary vascular volume

“…found a pulmonary embolism incidence of 25% in hospitalized patients ( 7 ), while a systematic literature search identified in 27 studies with 3,342 patients a prevalence of 16.5% in all patients scanned for COVID-19 ( 9 ). Recently, Nevesny et al ( 17 ) highlighted a potential connection between pulmonary embolism and venous congestion in the affected territories without arterial dilatation ( 17 ). More importantly, Nevesny et al demonstrated that vascular congestion primarily happens in the venous compartment in COVID-19 pneumonia, with normal caliber veins in the non-affected zones, directing the discussion of pathophysiology towards specific mechanisms.…”

“…Images were acquired with the following parameters: rotation speed, 0.5 s; voltage, 80/140 kVp; tube load, 249 to 485 mAs; reconstructed slice thickness, 1.25 mm; and section interval, 1 mm; 80 keV. 60 to 100 mL (depending on patient’s size and weight at the discretion of the radiology technician in charge) of iodinated contrast material (Accupaque 300 ® , GE Healthcare, Oslo, Norway) were injected intravenously followed by a saline chaser ( 17 , 25 ). All exams were acquired to enhance both pulmonary and systemic vessels, using the bolus tracking technique to trigger the acquisition as per routine protocols applied in the department.…”

“…Vascular volumes were extracted using CT number thresholds to isolate voxels containing vascular elements. Because of interpatient variability, the CT number threshold (in Hounsfield Units [HU]) was contrast enhancement-dependent and manually defined, in order to separate as much as possible densities corresponding to vascular structures, i.e., pulmonary arteries, pulmonary veins and to a lesser extent systemic arteries which account for a lower portion of the vessels as previously demonstrated ( 17 ), from the densities corresponding to parenchyma. Figure 1 summarizes the lung volume and vascular segmentation processes.…”

“…Patients were recruited from the Swiss national registry coronavirus-associated vascular abnormalities (COVID-CAVA; clinicaltrials.gov identifier NCT04824313), a multicentric cohort of patients who underwent chest CT and had microbiologically-proven COVID-19 infection, with the aim to assess non-vascular and vascular findings (25). In this cohort, we already demonstrated that vascular congestion observed in COVID-19 primarily affects veins, but without quantitatively comparing the fraction of vascular components in affected vs. non-affected lung segments (17). We consecutively included 24 patients from the 12th of March to the 28th of April 2020 from the Lausanne University Hospital Center (CHUV), Lausanne, Switzerland.…”

“…While the computed tomography (CT) pulmonary manifestations of the Coronavirus disease 2019 (COVID-19) have been widely described (1)(2)(3)(4)(5)(6), vascular manifestations have been less frequently reported and remain poorly understood. Multiple vascular changes are described in the literature, including mainly pulmonary embolism (7-10), vascular congestion or enlargement (11)(12)(13)(14)(15)(16)(17), and perfusion changes (18)(19)(20)(21). Until now, the link between morphological changes and the correlation between biological changes and virus-induced inflammatory disorders remains an area of research.…”