In patients with atrial fibrillation, does use of aspirin in addition to an anticoagulant improve or worsen clinical outcomes?
Many patients with atrial fibrillation (AF) are receiving aspirin (A) in addition to an oral anticoagulant (OAC), despite the fact that 40% of the patients in this study had no indication for aspirin (eg, no known atherosclerotic disease). Concomitant use of aspirin increased the risk of bleeding over OAC alone (adjusted hazard ratio [aHR] = 1.5) without any clear benefit regarding cardiovascular events. This practice persists despite lack of support from randomized trials (the lone potential exception is the group of patients with a mechanical heart valve). This is a case in which less may be more, and randomized trials comparing OAC with A+OAC are needed in this population. (LOE = 2b)
Steinberg BA, Kim S, Piccini JP, et al, for the ORBIT-AF Investigators and Patients. Use and associated risks of concomitant aspirin therapy with oral anticoagulation in patients with atrial fibrillation: insights from the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF) Registry. Circulation 2013;128(7):721-728.
Most patients with AF are treated with an anticoagulant. Those who also have an indication for an antithrombotic, such as known coronary artery or cerebrovascular disease, may also be given aspirin. The benefit of this incremental therapy (aspirin plus oral anticoagulant [A+OAC]) is uncertain.The authors used a registry of 10,126 adult outpatients being treated for AF; those with reversible cause or short life expectancy were excluded. After also excluding those who were not taking an anticoagulant and those taking other antithrombotics, they were left with 4804 patients who were taking OAC and 2543 who were taking A+OAC. Those using combination therapy were more likely to be male (53% OAC, 66% A+OAC) and more likely to smoke, have hyperlipidemia, diabetes mellitus, or heart failure. A multivariate analysis found that those being given A+OAC had a higher likelihood of known coronary artery disease (adjusted odds ratio [aOR] = 2.2), previous ablation (aOR = 1.6), previous stent placement (aOR 1.5), or previous stroke or transient ischemic attack (aOR = 1.5). Older patients, those with long-standing or persistent AF, those living in the southern or western states, patients with liver or renal disease, and those being cared for by a primary care physician were less likely to be using combination therapy. Using an adjusted propensity score analysis, the authors also looked at the likelihood of adverse outcomes at 6 months between groups. Major bleeding (aHR = 1.5; 95% CI 1.2 – 2.0) and bleeding resulting in hospitalization [aHR = 1.5; 1.2 – 2.0) were both significantly more likely in patients receiving concomitant aspirin therapy. When limiting the analysis to only those patients with previous myocardial infarction (n = 947) or stroke (n = 1042), although the overall number of cardiovascular or bleeding events was small, there was no apparent difference in the likelihood of these events between groups.