May-Thurner syndrome and the risk of pulmonary embolism in patients with acute deep venous thrombosis

Abstract

Objective: Pulmonary embolism (PE) is the most common complication of deep venous thrombosis (DVT). May-Thurner syndrome (MTS) is known to increase the risk of DVT, but an association between MTS and PE has not been established. This study investigated an association between MTS and the risk of PE in patients with acute lower extremity DVT.

Methods: Between June 2014 and September 2016, there were 112 patients with DVT at our hospital who underwent venous angiography and computed tomography pulmonary angiography. Data related to the patients' demographics, risk factors, disease onset time, side of DVT, D-dimer level, Doppler ultrasound, venous angiography, and computed tomography pulmonary angiography were collected. Associations between MTS and PE were analyzed.

Results: The 112 DVT patients included 79 with MTS. The rate of DVT in the left lower extremity was higher in the MTS group (98.7%) than in the non-MTS group (48.5%; P < .001). PE was less common in the MTS group (50.6%) than in the non-MTS group (78.8%; P = .006). The multinomial logistic analysis revealed a significant negative correlation between MTS and PE. The correlation remained after applying adjustment models I, II, and III. Model I adjusted for risk factors, DVT side, and D-dimer tertile (odds ratio [OR], 0.17; 95% confidence interval [CI], 0.04-0.68; P = .0125); model II adjusted for sex, age, risk factors, onset time, DVT side, D-dimer level, and D-dimer tertile (OR, 0.15; 95% CI, 0.03-0.71; P = .0162); and model III adjusted for sex, age, risk factors, onset time, DVT side, D-dimer level, D-dimer tertile, iliofemoral DVT, mixed (both iliofemoral and femoropopliteal) DVT, and femoropopliteal DVT (OR, 0.35; 95% CI, 0.06-2.08; P = .2501).

Conclusions: DVT patients with concomitant MTS have a decreased risk of PE compared with those without MTS. This finding extends previous reports of increased PE risk after DVT and calls for better understanding of shared risk factors and underlying mechanisms.

Keywords: Deep venous thrombosis; May-Thurner syndrome; Pulmonary embolism.