OUP user menu

Initiation of warfarin in patients with atrial fibrillation: early effects on ischaemic strokes

Laurent Azoulay, Sophie Dell'Aniello, Teresa A. Simon, Christel Renoux, Samy Suissa
DOI: http://dx.doi.org/10.1093/eurheartj/eht499 First published online: 19 December 2013


Aims An increased risk of stroke was observed in two atrial fibrillation (AF) trials of oral factor Xa inhibitors, when patients were transitioned to open label warfarin at the end of the study. The objective of this study is to determine whether initiation of warfarin is associated with an increased risk of stroke in patients with AF.

Methods and results Using the UK Clinical Practice Research Datalink, a nested case–control analysis was conducted within a cohort of 70 766 patients with AF between 1993 and 2008. Stroke cases were randomly matched with up to 10 controls on age, sex, date of AF diagnosis, and time since AF diagnosis. Conditional logistic regression was used to estimate adjusted rate ratios (RRs) with 95% confidence intervals (CIs) of stroke associated with current warfarin use classified according to time since initiation of treatment (<30 days, 31–90 days, and >90 days), when compared with non-use. A total of 5519 patients experienced a stroke during follow-up. Warfarin was associated with a 71% increased risk of stroke in the first 30 days of use (RR: 1.71, 95% CI: 1.39–2.12), while decreased risks were observed with initiation >30 days before the event (31–90 days: RR: 0.50, 95% CI: 0.34–0.75 and >90 days: RR: 0.55, 95% CI: 0.50–0.61, respectively).

Conclusion Patients initiating warfarin may be at an increased risk of stroke during the first 30 days of treatment, supporting the biological plausibility of a transient hypercoagulable state at the start of the treatment, although additional studies are needed to confirm these findings.

  • Atrial fibrillation
  • Stroke
  • Warfarin
  • Hypercoagulable state
  • Population-based
View Full Text

Sign In

ESC members if your subscription is provided via the European Society of Cardiology, either as a member or an ESC Congress delegate, select the 'ESC Member and Congress Delegate Sign In' link in the list below. Discover if you are an ESC member here. Note: after sign in you will be redirected to the journal's home page. 'ESC member' will display at the top of the page to indicate you have full access rights for this session.

Otherwise, if your subscription is via OUP, enter your OUP username and password, or select an alternative sign in option below.

List of OpenAthens registered sites, including contact details.