Risks of stroke and mortality associated with suboptimal anticoagulation in atrial fibrillation patients

Arlene M. Gallagher; Efrosini Setakis; Jonathan M. Plumb; Andreas Clemens; Tjeerd-Pieter van Staa

doi:10.1160/TH11-05-0353

Thrombosis and Haemostasis, Table of Contents

Thromb Haemost 2011; 106(05): 968-977
DOI: 10.1160/TH11-05-0353

New Technologies, Diagnostic Tools and Drugs

Schattauer GmbH

Risks of stroke and mortality associated with suboptimal anticoagulation in atrial fibrillation patients

Authors

Arlene M. Gallagher

¹General Practice Research Database, Medicines and Healthcare products Regulatory Agency, London, UK
Efrosini Setakis

¹General Practice Research Database, Medicines and Healthcare products Regulatory Agency, London, UK
Jonathan M. Plumb

³Boehringer Ingelheim, Ingelheim am Rhein, Germany
Andreas Clemens

³Boehringer Ingelheim, Ingelheim am Rhein, Germany
Tjeerd-Pieter van Staa

¹General Practice Research Database, Medicines and Healthcare products Regulatory Agency, London, UK

²Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, the Netherlands

Abstract

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Summary

Atrial fibrillation (AF) carries an increased risk of ischaemic stroke, and oral anticoagulation with warfarin can reduce this risk. The objective of this study was to evaluate the association between time in therapeutic International Normalised Ratio (INR) range when receiving warfarin and the risk of stroke and mortality. The study cohort included AF patients aged 40 years and older included in the UK General Practice Research Database. For patients treated with warfarin we computed the percentage of follow-up time spent within therapeutic range. Cox regression was used to assess the association between INR and outcomes while controlling for patient demographics, health status and concomitant medication. The study population included 27,458 warfarintreated (with at least 3 INR measurements) and 10,449 patients not treated with antithrombotic therapy. Overall the warfarin users spent 63% of their time within therapeutic range (TTR). This percentage did not vary substantially by age, sex and CHA₂DS₂-VASc score. Patients who spent at least 70% of time within therapeutic range had a 79% reduced risk of stroke compared to patients with ≤30% of time in range (adjusted relative rate of 0.21; 95% confidence interval 0.18–0.25). Mortality rates were also significantly lower with at least 70% of time spent within therapeutic range. In conclusion, good anticoagulation control was associated with a reduction in the risk of stroke.

Keywords

Atrial fibrillation - anticoagulation - stroke - treatment - warfarin

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References

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