Background: Very few studies have evaluated thrombus burden quantitatively in acute pulmonary thromboembolism (APE).
Purpose: To evaluate thrombus burden quantitatively in APE by contrast-enhanced computed tomography (CECT) and clarify the associations among thrombus burden, thrombus location, and right heart strain, and their changes with direct oral anticoagulant (DOAC) treatment.
Methods: This study included the 28 PE patients who were treated by DOACs and could be evaluated regularly over time by CECT at St. Marianna University Hospital between January 2015 and May 2017. The proximal PE score was defined as follows. The pulmonary arteries were divided into 18 segments, each scored from 0 to 2 based on the severity of occlusion. The final score was calculated as the sum of each segment. As an index of distal pulmonary embolism, cross-sectional area (CSA) <5 mm2 (total area of small pulmonary vessels less than 5 mm2) was measured using Image J software. The ratio of the right ventricular diameter to the left ventricular diameter (RV/LV) was also calculated as an indicator of right heart strain.
Results: The proximal PE score increased significantly with APE severity (non-massive 12.1±7.0, sub-massive 22.2±5.2, massive 28.4±3.9, P<0.05). On the other hand, there was no significant difference in CSA <5 mm2 by APE severity (non-massive 367±121, sub-massive 425±138, massive 332±99, P=0.57). A strong correlation between the proximal PE score and RV/LV at baseline was observed (R=0.52, P<0.05), whereas no significant correlation between CSA <5 mm2 and RV/LV (R=-0.07, P=0.71) was observed. Marked improvements were observed after 6-month DOAC treatment in the proximal PE score (baseline, 18.3±8.8 vs. 6 months, 0.4±0.8, P<0.05), CSA <5 mm2 (baseline, 379±124 vs. 6 months, 464±127, P<0.05), and RV/LV (baseline, 1.12 ±0.34 vs. 6 months, 0.93±0.21, P<0.05). Proximal PE thrombus disappeared in 82% of the study patients.
Conclusion: Proximal PE had a greater effect on the severity and right heart strain than distal PE. Both proximal and distal PEs regressed with current DOAC treatment.
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