More than one in three atrial fibrillation (AF) patients at intermediate to high risk for stroke were treated with aspirin alone, despite previous data showing this therapy to be inferior to blood thinners, according to researchers at the University of California (UC) San Diego and UC San Francisco schools of medicine.
The study was published online June 20, 2016, in the Journal of the American College of Cardiology.
The study, which examined more than 200,000 outpatients with atrial fibrillation at risk for stroke treated by cardiovascular specialists, found that approximately 40 percent of AF patients were treated with aspirin alone. Previous studies have demonstrated this treatment option is not as beneficial as oral blood thinners such as warfarin for reduction of thromboembolism, an obstruction of a blood vessel by a clot that has become dislodged, most often from the heart in AF patients.
The incidence of stroke for AF patients is up to seven times greater than in those without the condition. In AF, electrical impulses in the upper chambers of the heart are chaotic, and the atrial walls quiver rather than contract normally in moving blood to the lower chambers. As a result, blood clots may form.
“Stroke prevention is critical to the management of AF patients. However, giving aspirin alone to this population may not be the best treatment therapy because it is either minimally effective or not effective at all and still comes with risks, such as intracranial hemorrhage,” said lead author Jonathan C. Hsu, MD, cardiologist and assistant clinical professor of medicine at UC San Diego School of Medicine. “Our study results show a gap in the appropriate treatment of AF patients at risk for stroke. The findings also highlight the critical need for cardiology specialists to adhere to standardized recommendations regarding the use of oral blood thinners instead of aspirin.”
Heart-related issues related to coronary artery disease (blockages of the heart arteries), including hypertension, dyslipidemia (abnormal amounts of fats in the blood) or a prior heart attack, were associated with more frequent prescription of aspirin only. Male sex, a higher BMI, a prior stroke and congestive heart failure were associated with more frequent prescription of blood thinners.
“The high rate of an aspirin-only prescription for AF patients with coronary artery disease and other stroke risk factors is concerning,” Hsu said. “It appears patients with more risk factors for having a stroke with AF are less likely to get the proper treatment, which is oral blood thinners.”
Hsu and his team also found approximately one third of AF patients in the study without significant coronary artery disease were prescribed both a blood thinner and aspirin, placing them at higher risk for bleeding without any evidence of benefit.
“The combination of drugs does not necessarily reduce cardiovascular events and stroke in an AF population and likely increases the risk of bleeding," Hsu said.
“Even the most knowledgeable physicians may find themselves in a bind when encountering a patient who needs antiplatelet drugs, such as aspirin, due to coronary disease and blood thinners for atrial fibrillation,” said senior author Gregory Marcus, MD, UCSF Health cardiologist and endowed professor in AF research in the UCSF School of Medicine. “While a large proportion of AF patients meeting the guideline indications for stroke prevention medications fail to receive them, a lack of sufficiently rigorous data regarding optimizing net clinical benefit among those with strong indications for both antiplatelet drugs and anticoagulants may in part be to blame.”
Both Hsu and Marcus add that concerns for bleeding may be the biggest reason for the underutilization of appropriate blood thinners in AF patients. However, the perception that aspirin by itself is sufficient or that the risk of aspirin plus a blood thinner is not worth the benefit may also be driving forces, and more studies of evaluating cardiovascular outcomes in AF patients prescribed aspirin only vs. oral blood thinners (or a combination of the two) are needed.
Other contributors to the Journal of the American College of Cardiology study include Thomas M. Maddox, MD, MSc, of the VA Eastern Colorado Health Care System, Colorado Cardiovascular Outcomes Research Consortium and University of Colorado School of Medicine; Kevin Kennedy, MS, Saint Luke’s Mid America Heart Institute; David F. Katz, MD, and Lucas N. Marzec, MD, University of Colorado School of Medicine; Steven A. Lubitz, MD, MPH, Massachusetts General Hospital; Anil K. Gehi, MD, The University of North Carolina at Chapel Hill; and Mintu P. Turakhia, MD, MAS, VA Palo Alto Health Care System/Stanford University School of Medicine.
The research was funded in part by the American College of Cardiology National Cardiovascular Data Registry. Hsu reports receiving honoraria from Medtronic, St. Jude Medical and Janssen Pharmaceuticals, and consulting fees from Celladon. Turakhia reports research support from Veterans Affairs, Gilead Sciences, iRhythm, Medtronic, Janssen Pharmaceuticals and SentreHeart, is a consultant to Janssen Pharmaceuticals, Medtronic, St. Jude Medical and Precision Health Economics, and has equity ownership in Thryva and Zipline. Marcus reports research support from the National Institutes of Health, Patient-Centered Outcomes Research Institute (PCORI), Medtronic, Pfizer, Rhythm Diagnostic Systems and SentreHeart, and is a consultant and has equity ownership in InCarda.
About UC San Diego Health Sciences
University of California, San Diego Health Sciences comprises clinical and academic entities – UC San Diego Health System, the region’s only academic health system; UC San Diego School of Medicine, one of the nation’s top research-intensive schools of medicine; and Skaggs School of Pharmacy and Pharmaceutical Sciences. The National Institutes of Health (NIH) ranks UC San Diego Health Sciences as one of the top two institutions in research funding per faculty member, and the School of Medicine is listed ninth in total NIH research funding. Part of The University of California System, UC San Diego – founded in 1960 – is renowned for collaborative and cross-disciplinary research that transcends traditional boundaries in science, engineering and the humanities.
UC San Francisco (UCSF) is a leading university dedicated to promoting health worldwide through advanced biomedical research, graduate-level education in the life sciences and health professions, and excellence in patient care. It includes top-ranked graduate schools of dentistry, medicine, nursing and pharmacy; a graduate division with nationally renowned programs in basic, biomedical, translational and population sciences; and a preeminent biomedical research enterprise. It also includes UCSF Health, which comprises two top-ranked hospitals, UCSF Medical Center and UCSF Benioff Children’s Hospital San Francisco, and other partner and affiliated hospitals and healthcare providers throughout the Bay Area.