Study suggests ASA plus OAC is effective in mechanical heart valve patients, but increases risk of bleeding


The combination of aspirin (ASA) and oral anticoagulation (OAC) significantly reduces the odds of thromboembolism, but has no effect on all-cause mortality versus OAC alone, according to a systematic review and meta-analysis.

Key Points

The current treatment recommendation for patients with chronic atrial fibrillation (AF) and those at high risk for stroke is combination therapy for prevention of thromboembolism with ASA plus OAC only when the patient has a mechanical prosthetic heart valve (eg, caged ball or caged disk valves), has had a thromboembolic event despite therapeutic anticoagulation, or if additional risk factors are present. However, combination therapy (ASA plus OAC) is being used with increased frequency in patients with chronic AF and concomitant coronary artery disease (CAD). Because ASA provides a complimentary anti-thrombotic effect to OAC via its anti-platelet effects, the combination is thought to be particularly beneficial in patients with CAD.

In this study, the authors conducted a systematic literature search of MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials through June 2005 to find studies of either OAC alone or combination ASA plus OAC with >3 months of follow-up and reported clinical events (arterial thromboembolism, mortality, or major bleeding).

ASA plus OAC significantly increased the odds of major bleeding versus OAC alone (OR=1.43; 95% CI, 1.00–2.02). There were no significant differences in the odds for intracranial bleeding (OR=1.36; 95% CI, 0.55–3.32) or fatal bleeding (OR=1.20; 95% CI, 0.42–3.46) with combination therapy.

"For patients receiving OAC therapy, the current practice of adding ASA to their treatment should be considered carefully," the authors stated. "The benefits in reducing thromboembolic events should be weighed against the increased risk of major bleeding."

Approximately 2.5 million people in the United States have chronic AF, 30% to 40% of whom have concomitant CAD, and 10% to 15% of whom are at high risk for stroke. Thus, appropriate selection of anti-thrombotic therapy is paramount in the treatment of these patients to maximize therapeutic benefit while minimizing significant bleeding risk.

SOURCE Dentali F, Douketis JD, Lim W, Crowther M. Combined aspirin-oral anticoagulant therapy compared with oral anticoagulant therapy alone among patients at risk for cardiovascular disease: A meta-analysis of randomized trials. Arch Intern Med. 2007;167:117–124.

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