Risk Factors for Stroke and Thromboembolism in Relation to Age Among Patients With Atrial Fibrillation: The Loire Valley Atrial Fibrillation Project

Abstract

Background 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. Methods 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. Results 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). Conclusions 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. 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.