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Residual Thrombosis to Guide the Duration of Anticoagulation
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What is the problem and what is known about it so far?
Deep venous thrombosis (DVT) occurs when blood clots form in the large leg veins. Pieces of these clots can break off and travel to the lungs and cause serious illness or death. Physicians use blood thinners (anticoagulants) to help dissolve the clots and prevent more clots from forming. The optimal duration of anticoagulant therapy for DVT is unclear.
Why did the researchers do this particular study?
To see which of 2 strategies better prevents recurrent clots over the long term in adults with DVT.
Who was studied?
538 patients who had already completed 3 months of anticoagulant therapy for DVT.
How was the study done?
The researchers randomly assigned patients to a fixed- or flexible-duration, ultrasonography-guided treatment strategy. Depending on the underlying cause of the DVT, patients in the fixed-duration group received either no additional treatment or 3 more months of anticoagulation (warfarin). Patients in the flexible-duration group had no further treatment if ultrasonography showed dissolved leg clots (recanalized veins) and continued anticoagulation with warfarin for 9 to 21 months if repeated ultrasonography showed persistent clots (residual thrombosis). The researchers followed patients for 33 months to assess recurrent clots and bleeding complications.
What did the researchers find?
More patients assigned to the fixed-duration group than the flexible-duration group had recurrent clots (17% vs. 12%). Slightly fewer patients assigned to the fixed-duration group had major bleeding complications (0.7% vs. 1.5%).
What were the limitations of the study?
There may have been too few participants to detect potentially important differences between groups in bleeding complications. The findings may not apply to patients with a history of several episodes of DVT or permanent risk factors for DVT because these patients were not studied.
What are the implications of the study?
Ultrasonography findings could help guide further treatment duration in patients who have already received anticoagulation for DVT for 3 months.
Article and Author Information
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The summary below is from the full report titled “Residual Thrombosis on Ultrasonography to Guide the Duration of Anticoagulation in Patients With Deep Venous Thrombosis. A Randomized Trial.” It is in the 5 May 2009 issue of Annals of Internal Medicine (volume 150, pages 577-585). The authors are P. Prandoni, M.H. Prins, A.W.A. Lensing, A. Ghirarduzzi, W. Ageno, D. Imberti, G. Scannapieco, G.B. Ambrosio, R. Pesavento, S. Cuppini, R. Quintavalla, and G. Agnelli, for the AESOPUS Investigators.
