Unprovoked proximal venous thrombosis is associated with an increased risk of asymptomatic pulmonary embolism

Pulmonary embolism (PE) is common in patients with deep venous thrombosis (DVT). The outcome of DVT with concomitant symptomatic PE is worse than the outcome of isolated DVT. The risk factors for DVT and simultaneous asymptomatic PE have not been systematically studied yet.

To evaluate the frequency and risk factors for asymptomatic PE in patients with DVT.

In 155 consecutive patients with a first episode of DVT and no PE symptoms, a ventilation-perfusion lung scan was performed. Body mass index (BMI) and waist-to-hip ratio (WHR) were calculated and concentrations of D-dimer, high-sensitivity CRP (hsCRP), tissue plasminogen activator (t-PA) and troponin were measured. Laboratory tests for thrombophilia were performed.

Asymptomatic PE was present in 36% of patients. No differences in gender, age, BMI and WHR were found between the patients with and without PE. PE was more common in patients with proximal DVT than in those with distal DVT (42% vs. 17%, p<0.01), and in patients with unprovoked DVT compared to patients with provoked DVT (51% vs. 28%, p<0.01). The risk of silent PE was the highest in patients with unprovoked proximal DVT (OR, 6.9; 95% CI, 2.3-21.0). Patients with asymptomatic PE had significantly higher values of D-dimer, hsCRP, t-PA and troponin than patients with isolated DVT.

Asymptomatic PE affected more than one third of patients with a first DVT. Unprovoked proximal DVT is the most important risk factor for the occurrence of silent PE.