Previous research shows that aspirin is not as beneficial as oral anticoagulant agents for reducing thromboembolism risk.

Atrial fibrillation (AF) is the most common cardiac arrhythmia worldwide and is associated with a significant risk for stroke. “Among patients with AF who are at intermediate or high risk for thromboembolism, national guidelines recommend that clinicians use anticoagulation with warfarin or the newer non-vitamin K antagonist oral anticoagulant agents (OACs) to help reduce morbidity and mortality,” explains Jonathan Hsu, MD, MAS. Little is known, however, about the extent to which AF patients at risk for stroke are prescribed only aspirin and the factors that determine this prescribing practice.

A Closer Look

For a study published in the Journal of the American College of Cardiology, Dr. Hsu and colleagues investigated the prevalence and predictors of treatment with aspirin only versus OAC therapy in AF patients at risk for stroke. The authors used 2008-2012 data from the National Cardiovascular Data Registry’s Practice Innovation and Clinical Excellence (PINNACLE) study. The data from PINNACLE allowed the research team to examine patterns of aspirin and OAC prescriptions among outpatients with AF who are being treated by cardiovascular specialist practices throughout the United States. It also enabled them to look at use of other antiplatelet agents.

“Of the more than 210,000 patients with AF in the study who had a high risk for stroke, about 38% to 40% were treated with aspirin only instead of an oral anticoagulant,” says Dr. Hsu. “Coronary atherosclerosis-related comorbidities—including hypertension, dyslipidemia, coronary artery disease, and prior myocardial infarction, among other factors—were associated with more frequent prescriptions of aspirin only. Factors associated with more frequent prescriptions of OACs included male sex, higher BMI, prior stroke or transient ischemic attacks, prior systemic embolism, and congestive heart failure.”

According to Dr. Hsu, the findings have important implications for AF patients, especially in light of the fact that the benefits of reducing stroke risks with OAC over aspirin increase as annual stroke risks rise. “The data draw attention to the high rate of prescribing aspirin in AF patients at risk for stroke despite previous data showing that aspirin is inferior to OAC in these individuals,” he says.

Improvement Warranted

Much of the underutilization of appropriate anticoagulant agents may be driven by either the perception that aspirin alone is sufficient or that the risk of OAC anticoagulation is not worth potential benefits, which may be miscalculated. “Regardless of the reasons, it’s clear that there appears to be a lack of a guideline adherence to prescribing OACs in cardiovascular specialist practices,” Dr. Hsu says.  “We need to identify opportunities to improve appropriate prescriptions of OACs instead of aspirin in AF patients and act on them to improve patient outcomes.” He notes that such efforts include identifying knowledge gaps that might be informed by future studies and focusing on factors at the practice level—rather than just the individual physician level—to improve prescription rates for OACs in AF patients who are at risk for stroke.