The rate of resolution of clot burden measured by pulmonary CT angiography in patients with acute pulmonary embolism

Abstract

Objective: The purpose of this article is to quantitatively assess the rate of resolution of clot burden detected on pulmonary CT angiography (CTA) in patients with acute pulmonary embolism (PE).

Materials and methods: We evaluated 111 consecutive patients (55 men and 56 women) in a retrospective cohort who were diagnosed with PE by pulmonary CTA and had at least one follow-up pulmonary CTA within 1 year. Two radiologists in consensus measured the volume of each clot using a semiautomated quantification program. Semiquantitative measures of clot burden were also computed. The resolution rates of the total clot volume, as well as clot volumes of the central (main and lobar) and peripheral vessels (segmental and subsegmental), were analyzed.

Results: The mean (± SD) clot volume per study was 3403.3 ± 6505.6 mm(3) at baseline and 531.6 ± 2383.5 mm(3) at the follow-up pulmonary CTA. Overall, 85 patients (77% ) showed complete resolution at the follow-up pulmonary CTA. Complete resolution was seen in 17 of 30 patients (56.7%) at a follow-up interval of 1-14 days, in 24 of 31 patients (77.4%) at 29-90 days, and in 32 of 34 patients (94.1%) after 90 days. The total clot volume measurements summed for all patients decreased by 78% (central clot, 69.4%; peripheral clot, 86.0%) at 14 days, by 96.6% (central clot, 93.4%; peripheral clot, 100%) at 90 days, and by 97.7% (central clot, 95.9%; peripheral clot, 100%) after 90 days.

Conclusion: Clot burden resolved completely in 77% of patients during the follow-up period. Our analysis showed that clots resolved faster in the peripheral arteries than in the central pulmonary arteries.

Figures

Fig. 1

Changes in measures of clot burden over time. A and B, Graphs show mean percentage change in total clot volume (A), calculated as [(baseline volume – follow-up volume) / baseline volume] × 100, and semiquantitative Qanadli [5] and Mastora [6] scores (B).

Fig. 2

47-year-old woman with acute pulmonary embolism and deep venous thrombosis. A, Baseline pulmonary CT angiography (CTA) shows thrombus (arrow) within segmental branches of left lower lobes. Total clot volume is 712.64 mm3. B, Follow-up pulmonary CTA obtained 73 days after baseline shows residual clot (arrow) in same location. Total clot volume is 320.25 mm3.

Fig. 3

56-year-old woman with malignancy who presented with acute pulmonary embolism. A, Baseline pulmonary CT angiography (CTA) shows clots in main and right pulmonary arteries and left pulmonary arteries (arrows). Total clot volume is 717.48 mm3. B, Follow-up pulmonary CTA obtained 105 days after baseline pulmonary CTA shows complete resolution.

Fig. 4

Changes in clot volume over time by location. A and B, Graphs show changes in clot volumes in central (A) and peripheral (B) pulmonary arteries.