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.