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 co-hort 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 exten-sion 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 throm-bosis (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 throm-boembolic complications at 3 months (pulmonary embolism, 3 [0.5%]; DVT, 15 [2.8%]; extension of SVT, 18 [3.3%]; and recur-rence 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