Aspirin Often Prescribed Over Anticoagulation for Patients With Afib, Stroke Risk, Says Study

Deborah Brauser

June 24, 2016

LA JOLLA, CA – Contrary to guideline recommendations, many patients with atrial fibrillation (AF) at risk of stroke are still being treated with aspirin alone instead of oral anticoagulation, new research suggests[1].

The study of outpatients with AF from the National Cardiovascular Disease Registry (NCDR) Practice Innovation and Clinical Excellence (PINNACLE) showed that among the more than 210,000 with a CHADS2 score of 2 or higher, signifying intermediate to high risk for thrombosis, 61.8% received warfarin or a non–vitamin K antagonist oral anticoagulant. But that still left 38.2% (n=80,371) treated just with aspirin.

And further analysis of a cohort of almost 295,000 participants with a CHA2DS2-VASc score of 2 or higher showed that 40.2% were treated with aspirin alone.

After multiple adjustments, the investigators found that specific demographics could help predict which type of treatment a patient would receive, regardless of cohort. Having hypertension, CAD, dyslipidemia, and a past MI were among the factors associated with aspirin instead of anticoagulant treatment (all P<0.001).

Factors associated with oral anticoagulation prescription included having a higher body mass index or being male (both comparisons, P<0.001). "Despite female sex being associated with a higher risk of stroke, males were treated more commonly with the proper therapy," lead author Dr Jonathan C Hsu (University of California, San Diego, La Jolla) told heartwire from Medscape.

"When it comes to patients with atrial fibrillation, I really feel that the biggest thing we should worry about is stroke. We thought aspirin might be overused in these patients, and that definitely turned out to be the case."

The findings were published online June 20, 2016 in the Journal of the American College of Cardiology.

It's "concerning that the highly motivated, conscientious, and talented cardiologists working in quality-conscious institutions . . . are not prescribing anticoagulation in one-third of their qualifying patients," write Drs Sanjay Deshpande and Samuel Wann (both from Columbia St Mary's Hospital, Milwaukee, WI) in an accompanying editorial[2].

" 'Take two aspirin and call me in the morning' is not appropriate treatment for a patient with atrial fibrillation at risk for thromboembolism," they add.

Predictive Factors

In the study, researchers assessed data from PINNACLE for 327,656 participants with AF—all of whom were enrolled from January 2008 through December 2012.

Cohort 1 included 210,380 participants with a CHADS2 score of at least 2, and cohort 2 included 294,642 participants with a score of 2 or greater on the newer CHA2DS2-VASc.

In addition to those mentioned earlier, other multivariable adjusted factors associated with being prescribed treatment with aspirin included having angina (stable or unstable), peripheral arterial disease or diabetes, or undergoing recent CABG.

Other factors linked to more frequent treatment with oral anticoagulation included having congestive heart failure, past stroke, transient ischemic attack, or systemic embolism.

The most commonly used oral anticoagulation treatment was warfarin (90.9% of the CHADS2 cohort, 90.6% of the CHA2DS2-VASc cohort), followed by dabigatran (Pradaxa, Boehringer Ingelheim)(7.2% and 7.4%, respectively) and rivaroxaban (Xarelto, Bayer/Janssen Pharmaceuticals) (1.9% and 2.0%, respectively).

"We were surprised by the prevalence of aspirin use in this patient population. I think this highlights an area that both prescribing clinicians and patients need to realize needs to be improved," said Hsu.

"I think some clinicians may feel that aspirin is good enough and protects a little bit against stroke. But that's not good enough."

"The Clot Thickens"

In an editorial subtitled, "The Clot Thickens," Deshpande and Wann write that using aspirin instead of anticoagulation leaves patients with "virtually no protection from stroke."

Although bleeding risk is often mentioned as a reason for not prescribing anticoagulation, "and that risk is real," that worry may be overestimated, they write.

In addition, patients "may discount their chances of suffering a disabling or fatal stroke, choosing less effective or ineffective treatment to prevent thromboembolism and failing to recognize that aspirin itself may cause bleeding."

Other possible reasons they cite include patient noncompliance with anticoagulant routines, confusing advertising messages, and the hope that "general preventive measures, such as diet and exercise . . . and yes, aspirin, is enough." They also mention guideline fatigue as a possible factor.

"But aspirin is not an anticoagulant [and] is ineffective in the prevention of thromboembolism related to nonvalvular atrial fibrillation," stress the editorialists.

The study was funded by the American College of Cardiology Foundation's NCDR. Bristol-Myers Squibb and Pfizer are founding sponsors of the PINNACLE registry. Hsu reports having received honoraria from St Jude Medical, Medtronic, Biotronik, Janssen Pharmaceutical, and Bristol-Myers Squibb, and research support from Biotronik and Biosense Webster. Disclosures for the coauthors are listed in the article. The editorialists report no relevant financial relationships.

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