During 3.6 years of mean follow-up , first occurrence of stroke , transient ischemic attack , or systemic embolism occurred in 386 patients.The strongest independent predictors of embolic events were age 75 years ( hazard ratio 2.55 ; confidence interval , 1.85-3 .53 ) , prior stroke or transient ischemic attack ( hazard ratio 2.07 ; 95 % confidence interval , 1.65-2 .60 ) , and female sex ( hazard ratio 1.37 ; confidence interval , 1.11-1 .69 ) .