Patients at Highest Stroke Risk Not Prescribed Blood Thinners

UCSF and UC San Diego Study is 'Wake-up Call' to Cardiologists

Nearly half of all atrial fibrillation (AF) patients at the highest risk for stroke are not being prescribed blood thinners by their cardiologists, according to a new study by researchers at the University of California (UC) San Diego and UC San Francisco schools of medicine.

The four-year study, which involved more than 400,000 participants, found that as stroke risk factor scores generally increased, cardiologists were more likely to prescribe blood thinners. But, AF patients with the highest risk for stroke were not prescribed oral anticoagulants as frequently as guidelines suggested.

“Despite a well-known association of AF with stroke, we found a significant lack of oral anticoagulant prescribed to reduce blood clots in high-risk patients. This is a wake-up call,” said lead author Jonathan C. Hsu, MD, cardiologist and assistant clinical professor of medicine at UC San Diego School of Medicine. “As the number of stroke cases in AF patients increase annually in the United States, our findings draw attention to a treatment gap in a demographic who may need these therapies the most.”

The incidence of stroke for AF patients is up to seven times greater than in those without the condition. Cardioembolic stroke is one of the main complications of AF, when stagnant blood in the left atrium of the heart forms a blood clot and is released into the circulation, where it blocks the flow to an organ, often the brain.

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. One in four adults over age 40 is at risk for AF, with a projection of nearly 6 million people in the nation having the condition by 2050.

Standardized recommendations are used to determine and help quantify an AF patient’s stroke risk and help treating physicians determine whether a prescription of oral medication, such as warfarin or newer blood thinners, may be warranted.

However, in this study, which was published online March 16, 2016, in JAMA Cardiology, researchers found that just under half (48 percent) of AF patients at the highest risk for stroke were not prescribed treatment.

“Well-informed and well-intended cardiologists may struggle with a lack of data regarding optimizing risks vs. benefits in patients with indications for anti-platelet drugs for their coronary artery disease and additional anticoagulants for their atrial fibrillation,” said senior author Gregory Marcus, MD, MAS, a UCSF Health cardiologist and endowed professor in AF research in the UCSF School of Medicine. “However, while studies specifically addressing those challenging patients are needed, it is clear that identifying barriers to anticoagulant prescription, whether they involve physician education or enhanced patient access, will be the key to rectifying the situation for the majority of patients.”

The authors said there are likely to be multiple reasons behind the practice, including the perceived risk of prescribing blood thinners in sicker patients.

“Physicians may be avoiding additional therapy in certain patients taking antiplatelet medications because of the increased risk of bleeding associated with the oral anticoagulants,” Hsu said. “It may be thought of as too dangerous for these sicker patients, but we still know that in most of these patients, the benefits of blood thinning to reduce the risk of stroke outweigh the risks of bleeding.”

Co-authors 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.

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.

About UCSF

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, as well as a preeminent biomedical research enterprise and UCSF Health, which includes two top-ranked hospitals, UCSF Medical Center and UCSF Benioff Children’s Hospital San Francisco, as well as other partner and affiliated hospitals and healthcare providers throughout the Bay Area. Please visit www.ucsf.edu/news.