How effective are dose-adjusted warfarin and aspirin for the prevention of stroke in patients with chronic atrial fibrillation?

Stephan Rietbrock; Jonathan M. Plumb; Arlene M. Gallagher; Tjeerd P. van Staa

doi:10.1160/TH08-08-0499

Thrombosis and Haemostasis, Table of Contents

Thromb Haemost 2009; 101(03): 527-534
DOI: 10.1160/TH08-08-0499

Cardiovascular Biology and Cell Signalling

Schattauer GmbH

How effective are dose-adjusted warfarin and aspirin for the prevention of stroke in patients with chronic atrial fibrillation?

An analysis of the UK General Practice Research Database

Authors

Stephan Rietbrock

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

²Boehringer Ingelheim, Ingelheim am Rhein, Germany
Arlene M. Gallagher

¹General Practice Research Database, Medicines and Healthcare products Regulatory Agency, London, UK
Tjeerd P. van Staa

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

³Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, the Netherlands

Abstract

Summary

The objective of this study was to evaluate the rate of stroke associated with aspirin and warfarin in routine clinical practice. The study included patients aged 40+ with chronic atrial fibrillation (cAF) registered in the UK General Practice Research Database. The outcome was the rate of stroke during current, past and no use of aspirin and warfarin. The study included 51,807 cAF patients. There was no difference in the rate of stroke between current and past use of aspirin (relative rate [RR]=1.04 [95% confidence interval (CI) 0.94 – 1.15]), while the rate of stroke was reduced during current warfarin use compared to past use (RR=0.62 [95% CI 0.54 – 0.71]). For warfarin, a pattern of lower rates of stroke during current exposure and higher rates with past exposure was seen only in patients treated for at least 6–12 months. For aspirin, no changes in the rates of stroke were observed with discontinuation of aspirin. The effectiveness of warfarin was dependent on the level of anticoagulation, with optimal risk reduction occurring within the recommended international normalised ratio (INR) range of 2.0 to 3.0. The proportion of patients achieving a stable INR within the target therapeutic range was at its lowest during the first three months of warfarin treatment. In conclusion, the results of this study support the effectiveness of warfarin treatment to reduce the rate of stroke in cAF patients in the general clinical practice setting, however the risk reduction is lower than that reported in clinical trials.

Keywords

Stroke prevention - epidemiological studies - risk factors

Full Text

References

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