Does extended oral anticoagulation after a pulmonary embolism reduce recurrent venous thrombosis?

By Robin Liang, PhD in TREC

samtake med doktor3The ideal duration of anticoagulation following an unprovoked pulmonary embolism is controversial.

Studies have shown that after anticoagulant therapy is stopped after 3 or 6 months following an unprovoked venous thromboembolism (VTE), patients have a much higher risk than those VTE events provoked by known risk factors. Previous studies have shown that extended therapy reduces the risk in these high-risk patients, but whether this benefit is maintained in the long-term has not yet been investigated.

The PADIS-PE (Prolonged Anticoagulation During Eighteen Months vs. Placebo After Initial Six-month Treatment for a First Episode of Idiopathic Pulmonary Embolism) Randomized Clinical Trial in France investigated the benefits and harms of an 18-month extension of anticoagulation following an initial 6-month treatment on a vitamin K antagonist for patients who had a first episode of unprovoked pulmonary embolism. Importantly, they also studied the outcomes for 24 months after the study treatments were discontinued.

During the treatment period, extended warfarin treatment did result in a reduced number of recurrences. The chance of having a recurrent VTE was 85 % lower in patients receiving extended therapy than in patients receiving placebo. A small risk of bleeding was higher in the warfarin-treated patients, but when the combined risk of recurrence and bleeding was taken into account the warfarin treatment was favorable (78% lower risk). During the follow-up period, a higher number of patients who had been on extended warfarin therapy had a recurrent episode of VTE. The rate of recurrent VTE during the median 24-month post-treatment follow-up was similar to that in the placebo group. Overall outcomes of the entire study, however, show that in the long-term there was no significant difference between those patients who were treated with warfarin and those who received a placebo over the 18-month extended period.

Ultimately, the study concludes that patients who did receive an additional 18-month treatment with warfarin had a reduced incidence of recurrent VTE. This benefit, however, was lost in the long term with the discontinuation of anticoagulation therapy. This study did not examine the effects of aspirin or newer anticoagulants – further research is required to evaluate the long-term effects of these drugs as secondary prophylaxis.

Reference: F. Couturaud et al. Six Months vs Extended Oral Anticoagulation After a First Episode of Pulmonary Embolism. JAMA. 2015;314(1):31-40.

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