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
Stephan Rietbrock
1  General Practice Research Database, Medicines and Healthcare products Regulatory Agency, London, UK
,
Jonathan M. Plumb
2  Boehringer Ingelheim, Ingelheim am Rhein, Germany
,
Arlene M. Gallagher
1  General Practice Research Database, Medicines and Healthcare products Regulatory Agency, London, UK
,
Tjeerd P. van Staa
1  General Practice Research Database, Medicines and Healthcare products Regulatory Agency, London, UK
3  Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, the Netherlands
› Author Affiliations
Financial support: The study was funded by Boehringer Ingelheim International GmbH (BI). BI has a compound in clinical development for stroke prevention in patients with atrial fibrillation.
Further Information

Publication History

Received: 05 August 2008

Accepted after major revision: 03 February 2008

Publication Date:
24 November 2017 (online)

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.