Ultrasonography may help tailor duration of anticoagulant therapy for DVT

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Tailoring the duration of anticoagulation on the basis of ultrasonography findings reduces the rate of recurrent venous thromboembolism (VTE) in adults with proximal deep venous thrombosis (DVT), according to a study in the May 5 issue of the Annals of Internal Medicine.

Paolo Prandoni, MD, PhD, from the University of Padua in Padua, Italy, and colleagues said that optimal anticoagulation strategies for DVT are evolving, and the researchers sought to assess whether tailoring the duration of anticoagulation on the basis of the persistence of residual thrombi on ultrasonography reduces the rate of recurrent VTE, compared with the administration of conventional fixed-duration treatment in adults with proximal DVT.

In a parallel, randomized trial, investigators from nine university or hospital centers in Italy examined 538 consecutive outpatients with a first episode of acute proximal DVT at completion of an uneventful three-month period of anticoagulation from 1999 to 2006. Trained physicians who assessed outcomes were blinded to patient assignment status, but patients and providers were not.

The researchers randomly assigned patients (stratified by center and secondary vs. unprovoked DVT by using a computer-generated list that was accessible only to a trial nurse) to fixed-duration anticoagulation (no further anticoagulation for secondary thrombosis and an extra three months for unprovoked thrombosis) or flexible-duration, ultrasonography-guided anticoagulation (no further anticoagulation in patients with recanalized veins and continued anticoagulation in all other patients for up to nine months for secondary DVT and up to 21 months for unprovoked thrombosis). For the primary outcome assessment, 530 patients completed the trial.

Overall, Prandoni and colleagues found that 17.2 percent of 268 patients allocated to fixed-duration anticoagulation and 11.9 percent of 270 patients allocated to flexible-duration anticoagulation developed recurrent VTE. For patients with unprovoked DVT, the adjusted HR was 0.61 and 0.81 for those with secondary DVT.

The researchers found that major bleeding occurred in 0.7 percent of patients in the fixed-duration group and 1.5 percent of patients in the flexible-duration group.

Based on the findings, the researchers concluded that ultrasonography findings may help tailor the duration of anticoagulant therapy for DVT.