Use and Associated Risks of Concomitant Aspirin Therapy with Oral Anticoagulation in Patients with Atrial Fibrillation: Insights from the ORBIT-AF Registry
Background—The role of concomitant aspirin therapy in patients with atrial fibrillation (AF) receiving oral anticoagulation (OAC) is unclear. We assessed concomitant aspirin use and its association with clinical outcomes among AF patients treated with OAC.
Methods and Results—The Outcomes Registry for Better Informed Treatment (ORBIT) of Atrial Fibrillation registry enrolled 10,126 AF patients from 176 US practices from June, 2010 through August, 2011. The study population was limited to those on OAC (n=7,347). Hierarchical multivariable logistic regression models were used to assess factors associated with concomitant aspirin therapy. Primary outcomes were 6-month bleeding, hospitalization, ischemic events, and mortality. Overall, 35% (n=2543) of AF patients on OAC also received aspirin (OAC+ASA). Patients receiving OAC+ASA were more likely male (66% vs. 53%, p<0.0001) and had more comorbid illness than those on OAC alone. Over one-third (39%) of OAC+ASA did not have a history of atherosclerotic disease, yet 17% had elevated ATRIA bleeding risk scores (≥5). Major bleeding (adjusted HR 1.53, 95% CI 1.20-1.96) and bleeding hospitalizations (adjusted HR 1.52, 95% CI 1.17-1.97) were significantly higher in those on OAC+ASA versus OAC alone. Rates of ischemic events were low.
Conclusions—Patients with AF receiving OAC are often treated with concomitant aspirin, even when they do not have cardiovascular disease. Use of OAC+ASA was associated with significantly increased risk for bleeding, emphasizing the need to carefully determine if and when the benefits of concomitant aspirin outweigh the risks in AF patients already on OAC.
Clinical Trial Registration Information—ClinicalTrials.gov. Identifier: NCT01165710.
- Received March 29, 2013.
- Revision received June 13, 2013.
- Accepted June 18, 2013.