Omission of aspirin from antiplatelet regimen: The WOEST study

Lifelong anticoagulation is necessary for the prevention of stroke in patients with rhythm disturbances and with mechanical valves. Patients who have a coronary stent implanted also need the antiplatelet drugs aspirin and clopidogrel to prevent the rare but lethal complication of stent thrombosis. For patients taking oral anticoagulant drugs (for atrial fibrillation or mechanical valve) who also have to undergo coronary stenting, the optimal antithrombotic treatment is still unknown, even though the use of all three drugs (oral anticoagulants, aspirin and clopidogrel) seems logical for the prevention of stroke and stent thrombosis. However, treatment with all three drugs often causes serious bleeding complications and the frequent need to discontinue the aspirin and clopidogrel.

Now, results from the WOEST study (What is the Optimal antiplatElet and anticoagulant therapy in patients with oral anticoagulation and coronary StenTing) show that a strategy of adding clopidogrel only to anticoagulants (and omitting aspirin) causes less bleeding and is safe with respect to preventing thrombotic and thromboembolic complications such as stent thrombosis. The results were presented here today at ESC Congress 2012 by Dr Willem Dewilde, TweeSteden Hospital, Tilburg, the Netherlands, who said that “WOEST is the first study demonstrating that the omission of aspirin in patients treated with oral anticoagulants and having a coronary stent is safe.”

He explained that the WOEST study was designed to resolve this specific dilemma of cardiology – the optimal antithrombotic treatment for patients taking oral anticoagulant drugs who also have to undergo coronary stenting. The study hypothesis was that aspirin could be omitted. “This would possibly lead to less bleedings,” said Dr Dewilde, “but hopefully would not increase the risk of thrombotic complications such as stent thrombosis.”

The study took place between November 2008 and November 2011, when 573 patients already treated with oral anticoagulants for atrial fiblillation or mechanical valves and undergoing coronary stenting were prospectively randomised to two groups: one given additional clopidogrel only (double therapy group), or a second given additional clopidogrel and aspirin (triple therapy group). Each was followed for one year. The investigator-driven study was conducted in 15 hospitals in the Netherlands and Belgium, and was sponsored by the St Antonius Hospital, Nieuwegein, the Netherlands.

Results showed that at one-year follow-up after coronary stenting, the dual therapy group had less bleeding and a lower overall mortality rate than the triple therapy group. Furthermore, there was no increase in the occurrence of myocardial infarction and stent thrombosis as compared with the triple therapy group.

“Thus,” said Dr Dewilde, “the WOEST study demonstrates that omitting aspirin leads to less bleedings but does not increase the risk of stent thrombosis, stroke or myocardial infarction. Although the number of patients in the trial is limited, this is an important finding with implications for future treatment and guidelines in this group of patients known to be at high risk of bleeding and thrombotic complications.”