Effectiveness of risk stratification according to CHADS2 score in Japanese patients with nonvalvular atrial fibrillation.

Cerebrovascular events increase with additional risk factors in patients with nonvalvular atrial fibrillation (NVAF). The relative risk proportional to the number of risk factors in Japanese patients has not been reported. The prevalence of risk factors was investigated for over 2 years in a prospective cohort study of 265 patients with NVAF. The CHADS2 score is a widely used risk stratification scheme that includes age, hypertension, diabetes mellitus, previous stroke, and heart failure. Cerebral infarction occurred in 23 patients. This group was significantly older and had a significantly higher prevalence of hypertension. The ratio of a CHADS2 score of 0 - 2 was 77% among patients without stroke, but 44% in the cerebral infarction group. Univariate logistic regression analysis showed that the predictive factors of cerebral infarction were: age (odds ratio (OR) 1.087 (confidence interval (CI) 1.032 - 1.145, P = 0.002), hypertension (OR 3.288 (CI 1.086 - 9.962, P = 0.03) and CHADS2 score (OR 1.762 (CI 1.222 - 2.543, P = 0.002). Furthermore, a CHADS2 score of 3 - 6 was associated with a greater risk of cerebral infarction (OR 4.420 (CI 1.838 - 10.631, P < 0.001). The CHADS2 score was a useful marker of stroke risk in this Japanese population. An increased CHADS2 score was associated with an approximate 1.8-fold increase in risk.