Use and Associated Risks of Concomitant Aspirin Therapy With Oral Anticoagulation in Patients With Atrial Fibrillation: Insights From the ORBIT-AF Registry
What is the rate of concomitant aspirin use, and what are the associated clinical outcomes, among atrial fibrillation (AF) patients treated with an oral anticoagulant (OAC)?
The authors reported data from the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF), which followed subjects with AF starting from enrollment between June 2010 and August 2011. For the purposes of this study, only subjects taking an anticoagulant were analyzed. Hierarchical multivariable logistic regression models were used to assess factors associated with concomitant aspirin therapy. Primary outcomes of interest were 6-month bleeding, hospitalization, ischemic events, and mortality.
Out of a total of 10,126 AF patients from 176 US practices entered into the registry, 7,347 were taking OAC. Of these, 2,543 (35%) were receiving concomitant aspirin therapy. In those taking concomitant aspirin and OAC, there were more males (66% vs. 53%, p < 0.0001), and more comorbid illness than those on OAC alone. There was a higher incidence of major bleeding (hazard ratio [HR], 1.53; 95% confidence interval [CI], 1.20-1.96), and more hospitalizations for bleeding (HR, 1.52; 95% CI, 1.17-1.97) among those on aspirin plus OAC versus OAC alone. The authors reported that more than one third (39%) of subjects taking aspirin plus OAC did not have a history of atherosclerotic disease.
The authors concluded that patients with AF receiving OAC are often treated with concomitant aspirin, even though they do not have cardiovascular disease. The authors further opined that use of aspirin plus OAC 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.
This analysis gives us important insights into the real-world experience with combining aspirin and OAC. This study joins other recent evidence suggesting that the bleeding risks of combining aspirin with an OAC probably outweigh the benefits, especially when there is little or no benefit to aspirin therapy, as in the case of primary prevention. The authors pointed out that over one third of the patients receiving aspirin on top of warfarin had no known atherosclerosis. As the use of OACs becomes more frequent, due to the rising incidence of AF and better recognition of the need for anticoagulation, we must become even more vigilant against the indiscriminate use of aspirin as preventive therapy.
Keywords: Risk, Atherosclerosis, Platelet Aggregation Inhibitors, Warfarin, Primary Prevention, Registries, Incidence, Cardiovascular Diseases, Confidence Intervals, Hemorrhage, Logistic Models
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