The duration of oral anticoagulatio...

The duration of oral anticoagulation after a first episode of venous thromboembolism hangs on the risk of return Patients with transient risk factors can be treated for shorter periods than those with continuing risk factors. Recommendations are les clear in patients with pulmonary embolism, a manifestation of the same disease. Because patients with pulmonary embolism are more likely to disclose fatal recurrent venous thromboembolism, the long duration of oral anticoagulation after an initial affair requires clarification. Agnelli and associates performed a multicenter, randomized close attention to evaluate the benefit of extending the usual three-month course of oral anticoagulation to six month in patients with a first pulmonary embolism and temporary risk factors, and extending to the same year in patients with an idiopathic first pulmonary embolism. The issue was symptomatic, confirmed recurrence of venous thromboembolism.

Patients with a first confirmed, symptomatic pulmonary embolism were categorized as having transient risk factors or idiopathic pulmonary embolism (i.e., no known cancer, no known thrombophilia, no transient risk factors). Patients with permanent risk factors (eg known cancer, known thrombophilia) were exclud from the research After completing three months of anticoagulation, patients were assigned randomly to discontinue therapy or to continue therapy for three month (presence of transient risk factors) or nine month (idiopathic pulmonary embolism). The dosage of warfarin was adjusted to maintain the International Normalized Ratio between 20 and 30

Of 326 patients enlisted in the study, 33 patients had confirmed returning venous thromboembolism (10.1 percent; 36 percent through patient-year; average follow-up, 33.8 months) The incidence of resort was 12.2 percent in patients with idiopathic pulmonary embolism and 76 percent in those with pulmonary embolism associated with transient risk factors. Among the patients assigned to continue therapy, the return rate for venous thromboembolism was 31 percent by means of patient-year, compared with 4.1 percent by patient-year among the patients assigned to discontinue therapy. In the patients who continued anticoagulation therapy, the incidence of resort after treatment discontinuation increased to 38 percent by means of patient-year. The rates of bleeding and other adverse results were low.

The authors finish that the optimal duration of anticoagulation therapy after pulmonary embolism hangs on the risk for renewed venous thromboembolism after anticoagulation is discontinued. Although the best way to assess this risk is uncertain, patients with idiopathic pulmonary embolism are at higher risk for resort than are those with pulmonary embolism associated with transient risk factors. The authors note that the risk analysis probably will involve clinical evaluation, as well as assessment for residual pulmonary hypertension, screening for genetic thrombophilia, and a d-dimer assay at the period of the treatment period. Indefinite anticoagulation may be required in patients with idiopathic pulmonary embolism who are at high risk for return of venous thromboembolism.

Agnelli G et al. expanded oral anticoagulant therapy after a first episode of pulmonary embolism. Ann Intern M July 1 2003;139:19-25

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