Association Between Thrombus Signal Intensity and Pulmonary Embolism in Patients With Proximal Deep Vein Thrombosis: A Magnetic Resonance Imaging Study.

Approximately 50% of deep vein thrombosis (DVT) occurrences in the lower extremity proximal veins are associated with pulmonary embolism (PE). The progression of proximal DVT is critical in PE development, as reflected by thrombus composition. Magnetic resonance black-blood thrombus imaging can identify venous thrombus components by displaying thrombus signal intensity variations. This study investigated the association between thrombus signal intensity and PE in patients with proximal DVT. A total of 126 patients with proximal DVT were recruited, and all underwent magnetic resonance black-blood thrombus imaging examination. The patients were divided into 2 groups: DVT-only and DVT with PE. The whole thrombus signal intensity ratio, proximal thrombus signal intensity ratio, distal thrombus signal intensity ratio, and thrombus volume were assessed. Histological analysis was performed to characterize the thrombus content. Logistic regression models were performed to evaluate the relationship between thrombus signal intensity and PE. Of the 126 eligible patients, 73 (58%) patients were in the DVT with PE group. Both proximal thrombus signal intensity ratio and whole thrombus signal intensity ratio were lower in the DVT with PE group compared with the DVT-only group (1.92±0.54 versus 1.31±0.42, P<0.001; 1.76±0.41 versus 1.62±0.36, P=0.034). The percentage of fibrin area (13.99±1.56% versus 7.51±1.25%, P=0.0087) and red blood cells area (49.65±18.8% versus 13.41±4.74%, P=0.0012) were higher in DVT with PE than DVT-only group. Univariate and multivariate logistic regression analysis showed that proximal thrombus signal intensity ratio remained statistically significant (odds ratio, 0.21 [95% CI, 0.12-0.39]; P<0.001). The proximal thrombus signal intensity ratio of the thrombus was independently associated with acute PE in patients with proximal lower extremity DVT, suggesting that thrombus components may be important in PE occurrence. These findings could provide novel insights for understanding DVT evolution.