Registry analysis finds physicians prescribe oral anticoagulants at lower rate than expected

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Nearly 40 percent of patients with atrial fibrillation who had an intermediate to high risk of stroke were treated with only aspirin, according to a registry analysis of more than 200,000 patients.

After adjusting for multiple variables, the following factors were associated with prescribing of aspirin alone: hypertension, dyslipidemia, coronary artery disease, prior MI, unstable and stable angina, recent CABG and peripheral arterial disease.

Meanwhile, the following factors were associated with prescriptions of oral anticoagulants: male sex, higher body mass index, prior stroke/transient ischemic attack, prior systemic embolism and congestive heart failure.

Lead researcher Jonathan C. Hsu, MD, of the University of California, San Diego, and colleagues published their results online in the Journal of the American College of Cardiology on June 20.

Previous research found that prescribing warfarin or oral anticoagulants reduces morbidity and mortality in patients with atrial fibrillation. Although studies have shown aspirin does not reduce the risk of thromboembolism as much as oral anticoagulants, the researchers said that prescriptions for oral anticoagulants are lower than expected.

For this study, the researchers used data from the National Cardiovascular Data Registry’s prospective PINNACLE registry, which the American College of Cardiology created in 2008. They identified patients with atrial fibrillation who enrolled in the PINNACLE registry between Jan. 1, 2008, and Dec. 30, 2012. They included patients with atrial fibrillation who were at moderate to high risk for thromboembolism, which they defined as a CHADS2 score of 2 or higher.

The final cohort included 210,380 patients from 123 practices in 38 states. Of the practices, 78.9 percent were in an urban/suburban setting, 22 percent were in the West, 13.8 percent were in the Northeast, 26.8 percent were in the Midwest and 37.4 percent were in the South.

They also conducted a secondary analysis that included 294,642 patients with atrial fibrillation and a CHA2DS2-VASc score of 2 or higher.

Of the patients with a CHADS2 score of 2 or higher, 38.2 percent were treated with aspirin alone and 61.8 percent were treated with warfarin or non-vitamin K antagonist oral anticoagulants. Of the patients with a CHA2DS2-VASc score of 2 or higher, 40.2 percent were treated with aspirin alone and 59.8 percent were treated with warfarin of non-vitamin K antagonist oral anticoagulants.

“Because 38.2% of [atrial fibrillation] patients with a CHADS2 score [of at least 2] were prescribed aspirin alone in our study, there is clearly a continued lack of a guideline-adhering prescription of [oral anticoagulants] in U.S. cardiovascular specialist practices,” the researchers wrote.

Of the patients treated with oral anticoagulants in the primary analysis, 90.9 percent used warfarin, 7.2 percent used dabigatran and 1.9 percent used rivaroxaban. In the secondary analysis, 90.6 percent of patients treated with oral anticoagulants received warfarin, while 7.4 percent received dabigatran and 2.0 percent received rivaroxaban.

Further, approximately 20 percent of patients who were prescribed aspirin also were prescribed dual antiplatelet therapy.

The researchers cited a few limitations of the study, including that the registry does not contain data on renal insufficiency or aspirin dose prescribed. They also could not calculate a HAS-BLED score, which indicates bleeding risk in patients with atrial fibrillation.

In addition, they mentioned that practices are not required to enroll in the PINNACLE registry, so only motivated practices typically participate. Thus, the prescribing patterns in this study many not be generalizable to other practices. Further, the registry does not contain follow-up data on subsequent stroke or bleeding and other outcomes.

“These data indicate a gap in care, most prominent in patients with or at risk for coronary artery disease, and should draw attention to a high rate of prescription of aspirin therapy in [atrial fibrillation] patients at risk for stroke, despite previous data that show aspirin to be inferior to [oral anticoagulants] in this population,” the researchers wrote. “The specific patient characteristics associated with this practice, including those related to coronary artery disease, highlight opportunities to improve appropriate prescription of [oral anticoagulants] in [atrial fibrillation], including identifying knowledge gaps that might be informed by future studies.”