(A) Observed stroke rate and rate predicted by CHA2DS2-VASc and CHA2DS2-VASc-R: for African-American patients only. (B) Observed stroke rate and rate predicted by CHA2DS2-VASc and CHA2DS2-VASc-R: for non-African-American patients only. CHA2DS2-VASc = congestive heart failure, hypertension, age ≥75 years, diabetes, previous stroke, vascular disease, age 65 to 74, and female sex; CHA2DS2-VASc-R = congestive heart failure, hypertension, age ≥75 years, diabetes, previous stroke, vascular disease, age 65 to 74, female sex, and African American ethnicity.