Risk stratification schemes, anticoagulation use and outcomes: The risk - Treatment paradox in patients with newly diagnosed non-valvular atrial fibrillation

Abstract

Objective: To examine whether warfarin use and outcomes differ across CHADS 2 and CHA 2DS 2-VASc risk strata for non-valvular atrial fibrillation (NVAF). Design: Population-based cohort study using linked administrative databases in Alberta, Canada. Setting: Inpatient and outpatient. Patients: 42 834 consecutive patients ≥20 years of age with newly diagnosed NVAF. Main outcome measures: Cerebrovascular events and/or mortality in the first year after diagnosis. Results: Of 42 834 NVAF patients, 22.7% were low risk on the CHADS 2 risk score (0), 27.5% were intermediate risk (1), and 49.8% were high risk (≥2). The CHA 2DS 2-VASc risk score reclassified 16 722 patients such that 7.8% were defined low risk, 13.8% intermediate risk and 78.4% high risk. Of the elderly cohort (≥65 years) with definite NVAF visits (at least two encounters 30 days apart, n=8780), 49% were taking warfarin within 90 days of diagnosis. Warfarin use did not differ across risk strata using either the CHADS 2 (p for trend=0.85) or CHA 2DS 2-VASC (p=0.35). In multivariable adjusted analyses, warfarin use was associated with substantially lower rates of death or cerebrovascular events for patients with CHADS 2 scores of 1 (OR 0.52, 95% CI 0.41 to 0.67) or ≥2 (OR 0.61, 95% CI 0.53 to 0.71), or CHA 2DS 2-VASc scores of ≥2 (OR 0.60, 95% CI 0.53 to 0.68). Conclusions: In elderly patients with NVAF and elevated CHADS 2 or CHA 2DS 2-VASC scores, warfarin users exhibited lower rates of cerebrovascular events and mortality. However, warfarin use did not differ across risk strata, another example of the risk - treatment paradox in cardiovascular disease.