NEW ORLEANS — Women with atrial fibrillation were at higher thromboembolic risk than men in a large prospective study of patients with this most common of arrhythmias, Margaret C. Fang, M.D., reported at the annual scientific sessions of the American Heart Association.
This new finding from the Anticoagulation and Risk Factors in Atrial Fibrillation (ATRIA) study helps resolve a controversy over whether female gender is an independent risk factor for atrial fibrillation-related thromboembolic events, said Dr. Fang of the University of California, San Francisco.
Although atrial fibrillation (AF)is known to increase thromboembolic risk fivefold overall, the degree of risk varies among subgroups of affected patients.
Several schemes for stroke risk stratification in patients with AF—most notably, those based on data from the Framingham Heart Study and Stroke Prevention in Atrial Fibrillation (SPAF) study—rate women with AF as being at higher risk for ischemic stroke and other thromboembolic events than men with the arrhythmia. Women over age 75 are rated as being at particularly high risk. Other risk-stratification strategies, including the one developed by the Atrial Fibrillation Investigators group, don't consider female gender to be a risk factor, she explained.
ATRIA is a prospective cohort study involving 13,559 adults receiving treatment for AF at Kaiser Permanente of Northern California. During a median 2.4 years of follow-up, the annual rate of thromboembolism in women not on warfarin was 3.5%, compared with 1.8% among men not on the drug. Among patients over 75 who weren't taking warfarin, the thromboembolism rate was 5.0% per year in women and 2.9% per year in men. In patients younger than 75, the annualized rate was 1.7% in women and 1.1% in men.
After adjustment for stroke risk factors including hypertension, heart failure, and coronary disease, women with AF not on warfarin still had a highly significant 60% greater relative risk of stroke than men.