Recurrent venous thromboembolism after deep vein thrombosis: incidence and risk factors.

BACKGROUND The recurrence rate after deep vein thrombosis (DVT) is high and the risk factors for recurrent thromboembolic events have only been investigated on a small scale. OBJECTIVES To estimate the cumulative incidence of recurrent venous thromboembolic events after a first or a second DVT and to identify possible risk factors for recurrent venous thromboembolism. METHODS We prospectively followed up 738 consecutive patients with an objectively verified symptomatic DVT for 3.7 to 8.8 years. Medical records and death certificates for all patients were reviewed during follow-up and recurrent DVT and pulmonary embolism were registered. RESULTS The 5-year cumulative incidence of recurrent venous thromboembolic events was 21.5% (95% confidence interval [CI], 17.7%-25.4%) after a first DVT and 27.9% (95% CI, 19.7%-36.1%) after a second DVT. The 5-year cumulative incidence of fatal pulmonary embolism was 2.6% (95% CI, 1.1%-4.1%) after a first DVT. Proximal DVT (relative risk [RR], 2.40; 95% CI, 1.48-3.88; P<.001), cancer (RR, 1.97; 95% CI, 1.20-3.23; P<.001), and history of a venous thromboembolism (RR, 1.71; 95% CI, 1.16-2.52; P<.01) predicted an independently increased risk of recurrent events in multivariate survival analysis. Postoperative DVT (RR, 0.27; 95% CI, 0.13-0.55; P<.001) and a long duration of oral anticoagulation therapy (RR, 0.95; 95% CI, 0.92-0.98; P<.01) involved a smaller risk of recurrent events. Sex, age, initial antithrombotic therapy, or immobilization did not affect the risk of a recurrent event. CONCLUSIONS The recurrence rate after a symptomatic DVT is high. Patients with proximal DVT, diagnosed cancer, short duration of oral anticoagulation therapy, or a history of thromboembolic events had a higher risk of recurrent events, while patients with postoperative DVT had a lower recurrence rate. This knowledge could help identify patients who might benefit most from prolonged prophylactic treatment in various risk situations.