Extent of pulmonary thromboembolic disease in patients with COVID-19 on CT: relationship with pulmonary parenchymal disease

Abstract

Aim: To report the severity and extent of pulmonary thromboembolic disease (PTD) in COVID-19 patients undergoing computed tomography pulmonary angiography (CTPA) in a tertiary centre.

Materials and methods: This is a retrospective analysis of COVID-19 patients undergoing CTPA over a period of 27 days. The presence, extent, and severity of PTD were documented. Two observers scored the pattern and extent of lung parenchymal disease including potential fibrotic features, as well as lymph node enlargement and pleural effusions. Consensus was achieved via a third observer. Interobserver agreement was assessed using kappa statistics. Student's t-test, chi-squared, and Mann-Whitney U-tests were used to compare imaging features between PTD and non-PTD sub-groups.

Results: During the study period, 100 patients with confirmed COVID-19 underwent CTPA imaging. Ninety-three studies were analysed, excluding indeterminate CTPA examinations. Overall incidence of PTD was 41/93 (44%) with 28/93 patients showing small vessel PTD (30%). D-dimer was elevated in 90/93 (96.8%) cases. A high Wells' score did not differentiate between PTD and non-PTD groups (p=0.801). The interobserver agreement was fair (kappa=0.659) for parenchymal patterns and excellent (kappa=0.816) for severity. Thirty-four of the 93 cases (36.6%) had lymph node enlargement; 29/34 (85.3%) showed no additional source of infection. Sixteen of the 93 (17.2%) cases had potential fibrotic features.

Conclusion: There is a high incidence of PTD in COVID-19 patients undergoing CTPA and lack of a risk stratification tool. The present data indicates a higher suspicion of PTD is needed in severe COVID-19 patients. The concomitant presence of possible fibrotic features on CT indicates the need for follow-up.

Figure 1

Consort diagram illustrating the process of selecting patients for the final study population.

Figure 2

(a,b) Axial and coronal unenhanced CT images of the chest of a 76-year-old man admitted to the ward with COVID-19 and increasing O₂ requirements. Note bilateral diffuse crazy paving pattern (yellow circles) and lower-lobe-predominant asymmetrical consolidation (yellow arrows), in keeping with severe disease that is indeterminate for COVID-19. (b) The subsequent axial CTPA image confirming small subsegmental PE in the left lower lobe (red arrow). (c,d) Axial unenhanced CT images of 67-year-old man admitted to intensive care with COVID-19 and failure to respond to treatment. (c) No parenchymal abnormality in the upper lobes with (d) showing bilateral pleural effusions (blue arrows) with lower lobe predominant consolidation and collapse (yellow arrows), in keeping with non-COVID-19 pattern.

Figure 3

(a,b) Axial CTPA images of a 36-year-old woman presenting to the emergency department with breathlessness and haemoptysis. Note lower zone predominant peripheral and bronchocentric ground-glass opacification (red arrows) and consolidation with a perilobular pattern (yellow arrows). The pattern is in keeping with moderate classic COVID-19. (c,d) Axial CTPA images of a 37-year-old woman presenting to emergency department with breathlessness. Note bronchocentric (red arrow) and peripheral lower zone consolidation (purple arrows) with no ground-glass opacification. The pattern is in keeping with probable COVID-19, which is moderate in extent.

Figure 4

(a) Baseline chest X-ray and (b) two-week follow-up chest X-ray of an 84-year-old man with a history of COVID-19, re-presenting to the emergency department 4 days post-discharge with hypoxia and breathlessness. Note progressive consolidation and architectural distortion in the lower lobes occurring in the interval between the two films. (c,d) Axial unenhanced CT images of the chest in the same patient. Note peripheral consolidation with peri-lobular pattern (blue arrows) and bronchocentric ground-glass opacification with traction bronchiectasis (red arrows), architectural distortion (white arrow) with associated volume loss as seen by posterior retraction of the interlobar fissures (yellow arrows).