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 clin ical risk factors for recurrence during the initial 3 months of anticoagula nt therapy and knowledge of the time course of recurrence may help clinicia ns decide about the frequency of clinical surveillance and the appropriaten ess 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 pulmona ry embolism [PE]) who were followed up for 3 months after the start of anti coagulant therapy. All patients received initial treatment with unfractiona ted heparin or a low-molecular-weight heparin (reviparin) and a coumarin de rivative starting the first or second day of treatment, with a target inter national normalized ratio of 2.0 to 3.0. Results: Four independent clinical risk factors for recurrent VTE were iden tified: (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) oth er clinically significant medical disease (OR, 1.79; 95% CI, 1.00-3.21). Ol der age was associated with a decreased risk for recurrent VTE (OR, 0.76; 9 5% CI, 0.64-0.92). Previous VTE, sex, and idiopathic VTE were not risk fact ors for recurrence. In patients with DVT or PE, there was no significant di fference in the rates of recurrent nonfatal VTE (4.8% vs 4.1%; P = .62), ma jor 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 duri ng the initial 2 to 3 weeks after the start of treatment. Conclusions: During the initial 3 months of anticoagulant therapy, recurren t VTE is more likely to occur in patients with cancer, chronic cardiovascul ar disease, chronic respiratory disease, or other clinically significant me dical disease. Patients with PE are as likely to develop recurrent VTE as t hose with DVT; however, recurrence is more likely to be fatal in patients w ho initially present with PE.