Objective To examine whether warfarin use and outcomes differ across CHADS2 and CHA2DS2-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 CHADS2 risk score (0), 27.5% were intermediate risk (1), and 49.8% were high risk (≥2). The CHA2DS2-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 CHADS2 (p for trend=0.85) or CHA2DS2-VASC (p=0.35). In multivariable adjusted analyses, warfarin use was associated with substantially lower rates of death or cerebrovascular events for patients with CHADS2 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 CHA2DS2-VASc scores of ≥2 (OR 0.60, 95% CI 0.53 to 0.68).
Conclusions In elderly patients with NVAF and elevated CHADS2 or CHA2DS2-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.
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This study is based, in part, on de-identified data provided by Alberta Health and Wellness through the Alberta Cardiac Access Collaborative; however, the interpretation and conclusions contained herein do not necessarily represent the views of the government of Alberta nor Alberta Health and Wellness.
Funding JAE is supported by the Canadian Institutes of Health Research and Alberta Innovates-Health Solutions (AIHS). FAM is supported by AIHS.
Competing interests None.
Ethics approval Alberta Health Research Ethics Board.
Provenance and peer review Not commissioned; externally peer reviewed.
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