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Thursday, March 16, 2017

Patients with High-Risk Atrial Fibrillation and Potentially Treatable Strokes Are Not Receiving Anticoagulants, Study Finds


Eighty-four percent of patients who had an acute ischemic stroke and a history of atrial fibrillation were not receiving guideline-recommended therapeutic anticoagulation before the stroke, according to a new study published online on March 14 in the Journal of the American Medical Association.

Those who did receive adequate anticoagulation before the stroke had better stroke severity scores, lower in-hospital mortality, and better functional outcomes, the study authors found.

The findings, the study authors wrote, demonstrate that there are "potentially preventable strokes in high-risk patients with AF who either were not treated with anticoagulants or did not receive adequate anticoagulation" and "highlight the opportunities for stroke prevention by improving appropriate AF treatment."

Atrial fibrillation (AF) is a substantial, but potentially modifiable, risk factor for stroke, and guidelines recommend treatment for patients with AF with vitamin K antagonists (warfarin) and non-vitamin K antagonist oral anticoagulants (NOACs). Previous studies have suggested these medicines are underused, but they tended to examine treatment patterns for AF only post-stroke. The present study, instead, examines how patients with acute ischemic stroke were treated prior to the event.

"A substantial number of strokes may be due to underuse of or inadequate anticoagulation in AF," the study authors, led by Ying Xian, MD, PhD, assistant professor of neurology and assistant professor of clinical pharmacology at the Duke University Medical Center and Duke Clinical Research Institute, wrote.

For their retrospective, observational study, researchers at Duke analyzed 94,474 patients who were participating in the Patient-Centered Research into Outcomes Stroke Patients Prefer and Effectiveness Research (PROSPER) study. All participants had been diagnosed with AF, had a stroke between October 2012 and March 2015, and had been admitted to hospitals participating in the American Heart Association/American Stroke Association's Get With The Guidelines-Stroke registry program. The research assessed anticoagulant use in the study population at the time of hospital admission.

They found that 7,176 (7.6 percent) of participants were receiving warfarin, and 8,290 (8.8 percent) were receiving NOACs. That left 79,008 patients (83.6 percent) who were receiving no anticoagulation therapy. Moreover, among the 91,155 patients defined as having a high risk of stroke according to their CHA2DS2–VASc score, which is designed to estimate the risk of stroke in patients with AF, 83.5 percent were not receiving adequate therapeutic anticoagulation (either warfarin or NOACs) before their stroke.

Those patients who did receive adequate anticoagulation before a stroke had lower rates of moderate or severe stroke:  15.8 percent (warfarin) and 17.5 percent (NOACs) compared with 27.1 percent [no therapy), 24.8 percent (antiplatelet therapy only), and 25.8 percent (subtherapeutic warfarin). Likewise, patients who received anticoagulation had lower rates of in-hospital mortality: 6.4 percent (warfarin) and 6.3 percent (NOACs) compared with 9.3 percent (no therapy), 8.1 percent (antiplatelet therapy only), and 8.8 percent [subtherapeutic warfarin).

Finally, patients receiving anticoagulation pre-stroke had higher odds of a better functional outcome, defined as a modified Rankin score (a functional scale measuring degree of disability or dependence after stroke, with higher scores indicating worse outcomes) of 0-1 or 0-2 at discharge.

The researchers noted several limitations to their study. Among them, the fact that the study analyzed treatment prior to stroke prevented randomization; the study excluded patients with AF who did not have a stroke, which prevented a case-control design; and some patients did not have available measures of stroke severity or functional outcome.

Look for expanded coverage of this study in an upcoming edition of Neurology Today​.