NAMDRC

The National Association for Medical Direction of Respiratory Care

HOW LONG TO TREAT DVT OR PULMONARY EMBOLISM

The recent ACCP Guideline recommends a three month course of anticoagulation for an episode of DVT or pulmonary embolism (venous thromboembolism) which occurs in association with a transient risk factor such as surgery, trauma or oral contraceptive use. The guideline recommends extended anticoagulation (no definite stop date) in patients with unprovoked venous thromboembolism (VTE). A clinician needs to weigh the risk of recurrent VTE with the risk of bleeding from anticoagulation to decide whether an individual patient is appropriate for extended anticoagulation The risk of recurrent VTE after an unprovoked VTE event is grossly underestimated by most clinicians, with a recent study demonstrating a recurrence rate of 40.8% at 5 years (Pradoni, 2007).

Using multiple older studies of vitamin K antagonists, the ACCP Guideline categorized the risk of bleeding on anticoagulant therapy in a patient with no bleeding risk factors as 0.8% annual risk of major bleeding. Warfarin at a reduced intensity proved to be less efficacious than standard intensity warfarin with a similar risk of bleeding in a study by Kearon (2003).

Two recent studies of direct oral anticoagulants change the dynamics of the calculation of the risk to benefit ratio of extended anticoagulation. A randomized clinical trial of apixaban (Agnelli, 2013), demonstrated that a reduced dose of apixaban after an initial 6 to 12 months of anticoagulation was equally effective in reducing recurrent VTE. The rate of major bleeding were 0.5% in the placebo group, 0.2% in the 2.5 mg apixaban group and 0.1% in the 5 mg apixaban group.

A recently published large RCT by Weitz (NEJM, March 30, 2017) compared rivaroxaban at a treatment dose (20 mg) or a prophylactic dose (10 mg) with aspirin (100 mg) after completing 6 to 12 months of anticoagulation. Symptomatic recurrent VTE occurred in 1.2% of patients receiving 10 mg of rivaroxaban, 1.5% of patients receiving 20 mg of rivaroxaban, as compared to 4.4% in patients receiving aspirin. Rates of major bleeding were 0.5% in the group receiving 20 mg rivaroxaban, 0.4% in the group receiving 10 mg of rivaroxaban, and 0.3% in the aspirin group.

Extended anticoagulation after initial anticoagulation for unprovoked VTE is underutilized, resulting in a substantial burden of recurrent VTE. Full dose anticoagulation with vitamin K antagonists has a significant risk of major bleeding. Despite a favorable risk to benefit calculation for full dose anticoagulation in the ACCP Guideline, clinicians and patients have not embraced this approach. Direct oral anticoagulants at a reduced dose (after full dose treatment for 6 to 12 months) offer an effective and safe approach to extended anticoagulation.

James P. Lamberti, MD, FCCP
Disclosure: Speaker’s Bureau: Boehringer-Ingelheim and Janssen

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