Association Between Inferior Vena Cava-Involved Thrombosis, Severe Iliac Vein Stenosis, and Proximal Pulmonary Embolism in Patients With Deep Vein Thrombosis

To investigate the possible risk factors for proximal pulmonary embolism (PE) in patients with lower extremity deep vein thrombosis (LEDVT). A single-center, retrospective cohort study was conducted. Consecutive patients diagnosed with unilateral LEDVT and confirmed PE by computed tomography (CT) pulmonary angiography and indirect CT venography between September 2015 and January 2022 were included. Patient demographics, presentation of LEDVT, laboratory examination, thrombus characteristics, comorbidities and risk factors for LEDVT, and imaging findings were analyzed to determine the univariable and multivariable associations. The associations between thrombus location, stenosis, and proximal PE were assessed using a stratified analysis. A total of 115 eligible patients (60.08 ± 15.18 years, 59.1% male) were included. Of these patients, 40 (34.8%) were in the proximal PE group (proximal thrombus involved main or lobar pulmonary artery), and 75 (65.2%) were in the distal PE group (without main and labor pulmonary artery involvement). The univariable analysis showed that onset time of LEDVT symptoms ≤ 7 days (P = .041), inferior vena cava (IVC) involvement (P = .035), and severe iliac vein stenosis (IVS) (stenosis ratio > 61.3%) (P = .010) were associated with the occurrence of proximal PE. Further multivariant analysis showed that IVC involvement was associated with an increased odds of proximal PE (OR: 4.45, 95% CI: 1.083 − 18.248, P = .038), whereas severe IVS (stenosis ratio > 61.3%) was associated with a decreased odds of proximal PE (OR: 0.294, 95% CI: 0.110-0.783, P = .014). Among patients with unilateral LEDVT, IVC involvement increased the risk of proximal PE; patients with severe IVS (stenosis ratio > 61.3%) had a lower risk of developing proximal PE compared with distal PE; and severe IVS seemed to be a protective factor for proximal PE.