Superficial venous thrombosis and venous thromboembolism: a large, prospective epidemiologic study.

Background: Superficial venous thrombosis (SVT) is perceived to have a benign prognosis.

Objective: To assess the prevalence of venous thromboembolism in patients with SVT and to determine the 3-month incidence of thromboembolic complications.

Design: National cross-sectional and prospective epidemiologic cohort study. (ClinicalTrials.gov registration number: NCT00818688)

Setting: French office- and hospital-based vascular medicine specialists.

Patients: 844 consecutive patients with symptomatic SVT of the lower limbs that was at least 5 cm on compression ultrasonography.

Measurements: Incidence of venous thromboembolism and extension or recurrence of SVT in patients with isolated SVT at presentation.

Results: Among 844 patients with SVT at inclusion (median age, 65 years; 547 women), 210 (24.9%) also had deep venous thrombosis (DVT) or symptomatic pulmonary embolism. Among 600 patients without DVT or pulmonary embolism at inclusion who were eligible for 3-month follow-up, 58 (10.2%) developed thromboembolic complications at 3 months (pulmonary embolism, 3 [0.5%]; DVT, 15 [2.8%]; extension of SVT, 18 [3.3%]; and recurrence of SVT, 10 [1.9%]), despite 540 patients (90.5%) having received anticoagulants. Risk factors for complications at 3 months were male sex, history of DVT or pulmonary embolism, previous cancer, and absence of varicose veins.

Limitation: The findings are from a specialist referral setting, and the study was terminated before the target patient population was reached because of slow recruitment.

Conclusion: A substantial number of patients with SVT exhibit venous thromboembolism at presentation, and some that do not can develop this complication in the subsequent 3 months.

Primary Funding Source: GlaxoSmithKline, sanofi-aventis, and the Ministère Francais de la Santé et des Sports (Programme Hospitalier de Recherche Clinique).