Validation of risk stratification schemes for predicting stroke and thromboembolism in patients with atrial fibrillation: nationwide cohort study

• Published in: BMJ 2011-01, Vol.342 (7792), p.320-320
• Main Authors: Olesen, Jonas Bjerring, Lip, Gregory Y H, Hansen, Morten Lock, Hansen, Peter Riis, Tolstrup, Janne Schurmann, Lindhardsen, Jesper, Selmer, Christian, Ahlehoff, Ole, Olsen, Anne-Marie Schjerning, Gislason, Gunnar Hilmar, Torp-Pedersen, Christian
• Format: Article
• Language: English
• Subjects: Acute coronary syndromes; Age; Aged; Antagonists; Arrhythmias; Aspirin; Atrial fibrillation; Atrial Fibrillation - complications; Atrial Fibrillation - mortality; Cardiac arrhythmia; Cardiovascular disease; Chad; Classification; Cohort analysis; Cohort studies; Congestive heart failure; Coronary vessels; Diabetes; Diabetes mellitus; Drugs: Cardiovascular System; Electrocardiography; Epidemiologic Studies; Female; Fibrillation; Heart Failure; Hospital admissions; Hospitalization - statistics & numerical data; Humans; Hypertension; Kaplan-Meier Estimate; Male; Mortality; Patients; Predictive ability; Predisposing factors; Risk Assessment - standards; Risk factors; Risk groups; Statistics; Stratification; Stratigraphy; Stroke; Stroke - etiology; Stroke - mortality; Strokes; Substance abuse treatment; Thromboembolism; Thromboembolism - etiology; Thromboembolism - mortality; Validation; Venous Thromboembolism; Vitamin K; Vitamin K - antagonists & inhibitors
• ISSN: 0959-8138; 0959-535X; 1468-5833; 1756-1833
• DOI: 10.1136/bmj.d124

Objectives To evaluate the individual risk factors composing the CHADS2 (Congestive heart failure, Hypertension, Age≥75 years, Diabetes, previous Stroke) score and the CHA2DS2-VASc (CHA2DS2-Vascular disease, Age 65-74 years, Sex category) score and to calculate the capability of the schemes to predict thromboembolism.Design Registry based cohort study.Setting Nationwide data on patients admitted to hospital with atrial fibrillation.Population All patients with atrial fibrillation not treated with vitamin K antagonists in Denmark in the period 1997-2006.Main outcome measures Stroke and thromboembolism.Results Of 121 280 patients with non-valvular atrial fibrillation, 73 538 (60.6%) fulfilled the study inclusion criteria. In patients at “low risk” (score=0), the rate of thromboembolism per 100 person years was 1.67 (95% confidence interval 1.47 to 1.89) with CHADS2 and 0.78 (0.58 to 1.04) with CHA2DS2-VASc at one year’s follow-up. In patients at “intermediate risk” (score=1), this rate was 4.75 (4.45 to 5.07) with CHADS2 and 2.01 (1.70 to 2.36) with CHA2DS2-VASc. The rate of thromboembolism depended on the individual risk factors composing the scores, and both schemes underestimated the risk associated with previous thromboembolic events. When patients were categorised into low, intermediate, and high risk groups, C statistics at 10 years’ follow-up were 0.812 (0.796 to 0.827) with CHADS2 and 0.888 (0.875 to 0.900) with CHA2DS2-VASc.Conclusions The risk associated with a specific risk stratification score depended on the risk factors composing the score. CHA2DS2-VASc performed better than CHADS2 in predicting patients at high risk, and those categorised as low risk by CHA2DS2-VASc were truly at low risk for thromboembolism.