Oral Anticoagulation and Concomitant Use of Aspirin: Analysis of the ORBIT-AF Registry

With the rapid arrival in the past few years of the novel oral anticoagulants, there has been heightened attention paid to appropriate anticoagulation therapy in patients with atrial fibrillation (AF). In contrast, the concurrent use of aspirin in this patient population has been poorly characterized and largely neglected. Steinberg and colleagues¹ recently analyzed the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF) to better assess the relationship between concurrent aspirin use and oral anticoagulation. They found that more than one-third of AF patients in this large cohort were taking both types of drugs. The results were published online in Circulation.

From June 2010 to August 2011, 7347 patients in this registry who were receiving oral anticoagulation were eligible for the study. All patients who may have been taking oral antiplatelet agents (ie, clopidogrel, prasugrel, ticagrelor) were excluded. Of the eligible patients, 35% were also receiving aspirin (daily dose was 81 mg in 85% of patients, 325 mg in most of the rest). Patients taking aspirin and oral anticoagulation were more likely to be male and have more comorbid illnesses. Surprisingly, however, more than one-third of these patients (39%) did not have a prior history of percutaneous coronary intervention, MI, cerebrovascular events, or other clinical cardiovascular disease that might justify aspirin use under current ACC/AHA guidelines.² One caveat is that approximatley 30% of patients in this study had type 2 diabetes and aspirin may be indicated incertain high-risk diabetic patients; this breakdown of patients with diabetes was not reported in the study.

With respect to clinical outcomes, there was an approximately 1.5-fold increase in hazard for major bleeding and hospitalizations for bleeding events with a higher incidence of intracranial hemorrhage at 6-month follow-up among the patients receiving both agents.

The take-home points from the study are important for primary care physicians who treat patients with AF. First, the results underscore the overuse of aspirin in primary prevention without a clear evidence base or clinical guidelines reflecting this indication. Second, the increased bleeding risks conferred by aspirin use can’t be ignored, especially when combined with anticoagulation. The risks of concomitant aspirin use must be weighed carefully against the benefits for each patient on anticoagulation, whether a traditional vitamin K antagonist or a newer agent, is used. The results also stand as a clear reminder that during an office visit when reviewing medications, it is equally as important to consider what medications may be discontinued as those that may be added.


1. Steinberg BA, Kim S, Piccini JP, et al; Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF) Investigators and Patients. Use and associated risks of concomitant aspiring therapy with oral anticoagulation in patients with atrial fibrillation: insights from the ORBIT-AF Registry. Circulation. 2013 Jul 16; [Epub ahead of print]. (Abstract)

2. Redberg RF, Benjamin EH, Bittner V, et al. ACCF/AHA 2009 performance measures for primary prevention of cardiovascular disease is adults: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Performance Measures (Writing Committee to Develop Performance Measures for Primary Prevention of Cardiovascular Disease) developed in collaboration with the American Academy of Family Physicians; American Association of Cardiovascular and Pulmonary Rehabilitation; and Preventive Cardiovascular Nurses Association. Endorsed by the American College of Preventive Medicine, American College of Sports Medicine, and Society for Women's Health Research. J Am Coll Cardiol. 2009;54:1364-1405. (Full text article)

3. Mukherjee D, Rosenson RS, Williams CD, et al. Aspirin for primary prevention of cardiovascular events in people with diabetes: a position statement of the American Diabetes Association, a scientific statement of the American Heart Association, and an expert consensus document of the American College of Cardiology Foundation. Circulation. 2013;121:2694-2701. (Full text article)