Antiplatelet therapy in addition to a vitamin K antagonist (VKA) in patients with atrial fibrillation (AF) and stable coronary artery disease (CAD) may not lower the risk of recurrent coronary events or thromboembolism, according to a study published online Jan. 27 in Circulation.

Although American and European guidelines recommend adding two antiplatelet drugs in addition to vitamin K antagonists from a month to a year after a coronary event in certain circumstances, the researchers sought to determine whether long-term antithrombotic treatment with only VKA after a year with stable CAD led to a reduction in serious bleeding events without an increased risk of recurrent coronary events or thromboembolism compared to VKA with an antiplatelet agent.

Study investigators, led by Morten Lamberts, MD, PhD, of Copenhagen University Hospital Gentofte in Hellerup, Denmark, identified all AF patients hospitalized for an MI or PCI between 2001 and 2011 and excluded patients later hospitalized for MI or angina within 360 days. They followed patients with AF and stable CAD from 2002 through 2011 and only included patients taking antithrombotic therapy, defined as single antiplatelet therapy (aspirin or clopidogrel [Plavix, Bristol-Myers Squibb]); VKA only (warfarin or phenprocoumon [Marcoumar, Hoffmann-LaRoche]); dual antiplatelet therapy (aspirin and clopidogrel); VKA and single antiplatelet therapy (aspirin or clopidogrel); and VKA plus dual antiplatelet therapy.

The effectiveness outcomes were MI/coronary death and fatal or nonfatal thromboembolism. The main safety outcome was fatal or nonfatal bleeding. The researchers also defined a composite outcome of MI, thromboembolism, bleeding and all-cause mortality.

There were 8,700 patients included in the study who were followed up for an average of 3.3 years. The incidence rate was 7.2 for MI/coronary death, 3.8 for thromboembolism and 4 for serious bleeding. Compared with VKA alone, the risk of MI/coronary death was similar for VKA with aspirin (HR 1.12) and VKA with clopidogrel (HR 1.53). Thromboembolism risk was similar in all groups and the risk of bleeding was higher when aspirin or clopidogrel was used with VKA (HR 1.5 and 1.84 respectively).

Despite current guidelines, the authors argued that their study findings suggest that the “common practice of adding antiplatelet therapy to oral anticoagulation in patients with AF and stable CAD warrants reassessment.”