Question: Is anticoagulant treatment for calf vein thrombosis for 6 weeks duration associated with acceptable recurrence and safety outcomes? Is anticoagulant therapy for 3 months duration for proximal deep vein thrombosis (DVT) or pulmonary embolism (PE) associated with acceptable recurrence and safety outcomes?
Population: Men and women with a first episode of symptomatic calf vein thrombosis or proximal DVT confirmed by ultrasound or venography, or PE confirmed by lung scan or angiography. Patients with pregnancy, thrombophilia, severe PE, and cancer were excluded.
Design and methods: After treatment with heparin and oral anticoagulants targeting an INR of 2-3, patients with calf DVT were randomized to 6 weeks ( n = 105) versus 3 months ( n=92) of treatment, and patients with proximal DVT and/or PE were randomized to 3 months ( n = 270) versus 6 months ( n=269) of treatment. The outcome events were recurrences and major, minor, or fatal bleeding complications. The mean follow-up time was 12 months.
Results: A total of 736 patients were enrolled. For calf vein thrombosis the recurrence of DVT or PE after 6 weeks of therapy was 2/105 (2.0%) versus 3/92 (3.4%) with 3 months of therapy, relative risk of 0.58 (95% CI: 0.10-3.36). The rates of major bleeding were 1/105 (1.0%) and 3/92 (3.4%) respectively, relative risk of 0.29 (95% CI: 0.03-2.72). For proximal DVT or PE, the recurrence rate after 3 months of therapy was 21/270 (8.1%) versus 23/269 (8.7%) after 6 months of treatment, relative risk of 0.93 (95% CI: 0.53-1.65). The rates of major bleeding were 5/270 (1.9%) versus 7/269 (2.6%) respectively, relative risk of 0.73 (95% CI: 0.24-2.27).
Conclusion: After isolated calf vein DVT, 6 weeks of oral anticoagulation is sufficient. For proximal DVT or PE, 3 and 6 months of anticoagulant therapy is equivalent. For patients with temporary risk factors who have a low risk of recurrence, 3 months of treatment seems to be sufficient.