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Heart Rhythm. 2008 Oct;5(10):1365-72. doi: 10.1016/j.hrthm.2008.07.014. Epub 2008 Jul 17.

Epidemiology and outcomes in patients with atrial fibrillation in the United States.

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1
World Health Information Science Consultants, Wellesley, Massachusetts, USA.

Abstract

BACKGROUND:

Nonrheumatic atrial fibrillation (AF) is a common cause of embolic stroke. Warfarin therapy can reduce stroke risk by two-thirds in patients with AF, but therapy may not always be used or always be used optimally.

OBJECTIVES:

This study sought to document the patterns of anticoagulant use and the determinants and incidence of stroke, intracranial hemorrhage, and arterial thromboembolism in US patients with AF.

METHODS:

Using health insurance claims and laboratory results, we examined events per unit of person-time and used Poisson regression to quantify the association of AF outcomes with the international normalized ratio (INR) and other covariates.

RESULTS:

In 116,969 patients age > or =40 years with an insurance claim for AF or atrial flutter between 1999 and 2005, warfarin was prescribed to 45%, and 48% had no claim for any anticoagulant or antiplatelet agent. Subtherapeutic INR levels (<2.0) raised the incidence of stroke (relative risk [RR]: 2.39, 95% confidence interval [CI]: 1.68 to 3.41) and arterial thromboembolism (RR: 5.68, 95% CI: 1.88 to 17.10) compared with therapeutic INR levels, whereas supratherapeutic INR levels (>3.0) doubled the incidence of intracranial hemorrhage (RR: 2.11, 95% CI: 1.16 to 3.84). Further covariate adjustment had little effect on these estimates.

CONCLUSION:

Warfarin remains underused within the outpatient setting. Nontherapeutic INR levels are associated with increased risk of stroke, bleeding, and thromboembolism compared with therapeutic INR levels.

PMID:
18929320
DOI:
10.1016/j.hrthm.2008.07.014
[Indexed for MEDLINE]
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