According to the latest European guidelines on the management of nonvalvular atrial fibrillation (NVAF), all patients aged ≥ 65 years should be treated with oral anticoagulation (if not contraindicated). Therefore, stroke risk factors should be investigated exclusively in patients with NVAF aged < 65 years.
Patients diagnosed with NVAF in a four-hospital institution between 2000 and 2010 were identified. Event rates of stroke/thromboembolism were calculated according to age category (ie, age < 65, 65-74, and ≥ 75 years). Independent risk factors of stroke and thromboembolism were investigated in univariate and multivariate Cox regression models including patients with NVAF aged < 65 years only. The effect of adding vascular disease to the CHADS2 (congestive heart failure, hypertension, age ≥ 75 years, diabetes, previous stroke) score was examined by net reclassification improvement (NRI) and integrated discrimination improvement (IDI) models.
Among 6,438 patients with NVAF, 2,002 (31.1%) were aged < 65 years. In patients with no CHADS2 risk factors who were not treated with anticoagulation (n = 1,035), the stroke/thromboembolic event rate per 100 person-years was 0.23 (95% CI, 0.08-0.72), 2.05 (95% CI, 1.07-3.93), and 3.99 (95% CI, 2.63-6.06) in those aged < 65, 65-74, and ≥ 75 years, respectively. Heart failure, previous stroke, and vascular disease were significantly associated with increased risk of stroke/thromboembolism in both univariate and multivariate analyses, and vascular disease significantly improved the predictive ability of the CHADS2 score (NRI, 0.40; IDI, 0.031).
Patients with NVAF aged ≥ 65 years have event rates that merit oral anticoagulation. In patients with NVAF aged < 65 years, the risk of stroke/thromboembolism is independently increased by the presence of heart failure, previous stroke, or vascular disease. As proposed in the new CHA2DS2-VASc (congestive heart failure, hypertension, age ≥ 75 years, diabetes, previous stroke, vascular disease, age 65-74 years, sex category [female]) score, stroke risk stratification by the CHADS2 score can be improved by the addition of age 65 to 74 years and vascular disease.