Clinical risk factors and timing of recurrent venous thromboembolism during the initial 3 months of anticoagulant therapy

Background: In patients with venous thromboembolism (VTE), identifying clinical risk factors for recurrence during the initial 3 months of anticoagulant therapy and knowledge of the time course of recurrence may help clinicians decide about the frequency of clinical surveillance and the appropriateness of outpatient treatment. Methods: Analysis of a randomized controlled trial database involving 1021 patients with VTE (750 with deep vein thrombosis [DVT] and 271 with pulmonary embolism [PE]) who were followed up for 3 months after the start of anticoagulant therapy. All patients received initial treatment with unfractionated heparin or a low-molecular-weight heparin (reviparin) and a coumarin derivative starting the first or second day of treatment, with a target international normalized ratio of 2.0 to 3.0. Results: Four independent clinical risk factors for recurrent VTE were identified: (1) cancer (odds ratio [OR], 2.72; 95% confidence interval [CI], 1.39-5.32), (2) chronic cardiovascular disease (OR, 2.27; 95% CI, 1.08-4.97), (3) chronic respiratory disease (OR, 1.91; 95% CI, 0.85-4.26), and (4) other clinically significant medical disease (OR, 1.79; 95% CI, 1.00-3.21). Older age was associated with a decreased risk for recurrent VTE (OR, 0.76; 95% CI, 0.64-0.92). Previous VTE, sex, and idiopathic VTE were not risk factors for recurrence. In patients with DVT or PE, there was no significant difference in the rates of recurrent nonfatal VTE (4.8% vs 4.1%; P = .62), major bleeding (2.9% vs 2.2%; P = .53), and non-VTE death (6.4% vs 7.8%; P = .45), but recurrent fatal PE was more frequent in patients with PE than DVT (2.2% vs 0%; P<.01). There was a clustering of recurrent VTE episodes during the initial 2 to 3 weeks after the start of treatment. Conclusions: During the initial 3 months of anticoagulant therapy, recurrent VTE is more likely to occur in patients with cancer, chronic cardiovascular disease, chronic respiratory disease, or other clinically significant medical disease. Patients with PE are as likely to develop recurrent VTE as those with DVT; however, recurrence is more likely to be fatal in patients who initially present with PE.