Oral anticoagulant prescriptions increase with higher stroke risk

An analysis of a quality improvement registry of patients with atrial fibrillation found that a one-point increase in the CHADS2 score or the CHA2DS2-VASc score was associated with an approximately 15 percent greater adjusted odds of being prescribed an oral anticoagulant.

Lead researcher Jonathan C. Hsu, MAS, of the University of California, San Diego, and colleagues published their results online in JAMA Cardiology on March 16.

“Our findings have important implications for patients with [atrial fibrillation], particularly because annual stroke risk increases with the number of stroke risk factors measured by the CHADS2 score and the CHA2DS2-VASc score,” they wrote. “Therefore, the lack of guideline-adhering prescription of [oral anticoaglulants] for stroke prophylaxis in patients with the highest CHADS2 scores and CHA2DS2-VASc scores should draw attention to a treatment gap in patients who may most appropriately need [oral anticoagulant] therapy.”

The researchers mentioned that adults older than 40 years old have an estimated 1 in 4 lifetime risk of having atrial fibrillation, which is the most common cardiac arrhythmia. By 2050, approximately 5.6 million U.S. adults are expected to have atrial fibrillation.

For this study, the researchers evaluated 429,417 patients with atrial fibrillation who enrolled in the American College of Cardiology National Cardiovascular Data Registry’s PINNACLE (Practice Innovation and Clinical Excellence) registry between Jan. 1, 2008 and Dec. 30, 2012.

The registry, which was created in 2008, is the first national, prospective, office-based cardiac quality improvement registry in the U.S. Participating institutions collect longitudinal point-of-care data such as patient demographics, symptoms, comorbidities, vital signs, medications, laboratory values and recent hospitalizations, according to the researchers.

The mean age was 71.3 years old, and 55.8 percent of patients were males. They were from 144 academic and private cardiology practices in 38 states.

Of the patients, 44.9 percent were prescribed an oral anticoagulant, 25.9 percent were prescribed aspirin only, 5.5 percent were prescribed aspirin plus a thienopyridine and 23.8 percent were not prescribed any antithrombotic therapy.

Compared with the aspirin-only group, each one-point increase in the CHADS2 score was associated with a 15.8 percent increased odds of an oral anticoagulation prescription, while each one-point increase in CHA2DS2-VASc score was associated with a 16.3 percent increased odds of an oral anticoagulation prescription.

The oral anticoagulants included in this study were warfarin, dabigatran and rivaroxaban. Two other oral anticoagulants (apixaban and edoxaban) were not FDA-approved during the time this study took place.

The researchers mentioned that patients with atrial fibrillation who were prescribed an oral anticoagulant were more likely to be older, male, reside in the Northeast and Midwest and have a history of hypertension, dyslipidemia, congestive heart failure, diabetes, prior stroke or transient ischemic attack, prior systemic embolism and prior MI. They were less likely to have coronary artery disease, unstable angina, stable angina, peripheral arterial disease and prior CABG.

The study had a few limitations, according to the researchers, including that the registry did not capture data on medication use predisposing to bleeding, labile international normalized ratios or alcohol or drug use. The results of the study may not be generalizable to other cardiology practices, as well. The researchers also did not have information on previous bleeding complications or reasons for contraindications to anticoagulant therapy.

“These findings draw attention to important gaps in appropriate treatment of patients with [atrial fibrillation] at the highest risk of stroke and highlight opportunities to understand the reasons behind these gaps and insights to improve them,” they wrote.