Warfarin management in AF patients has improved
MedWire News: The rate of stroke in patients with atrial fibrillation (AF) who are taking warfarin has declined in recent years, say the authors of a meta-analysis.
The annual rate of stroke or systemic embolism in the current analysis was 1.66%, compared with 2.09% in a previously published meta-analysis, say Venu Menon (Cleveland Clinic, Ohio, USA) and colleagues.
"This reduction may be secondary to a considerable improvement in the quality of anticoagulation as reflected by a greater proportion of time spent in therapeutic anticoagulation," they write in the Archives of Internal Medicine.
The latest analysis includes patients from the warfarin arms of eight trials of anticoagulation in AF patients. The trials were conducted between 2003 and 2011, and included 32,053 patients.
The target international normalized ratio (INR) was 2.0-3.0 in all these studies, and the average proportion of time patients were within the target INR range (TTR) varied from 55% to 68%, with the average being above 60% for seven of the eight studies.
The previous meta-analysis included six studies published between 1989 and 1993. The target INR was variable, with the lower limit ranging from 1.4 to 2.8 and the upper limit from 2.7 to 4.5. The TTR ranged from 42% to 83%, with just two studies achieving an average above 60%.
Rates of major bleeding ranged from 1.40% to 3.40% in the current analysis and from 0.62% to 2.56% in the older analysis, but the definitions of major bleeding varied between individual studies.
In the latest analysis, the highest stroke rates occurred among elderly patients, women, patients with previous stroke, and those who had not previously used a vitamin K antagonist. Stroke rates also rose with increasing vascular risk, as assessed with the CHADS2 score.
In an accompanying commentary, Daniel Singer (Massachusetts General Hospital, Boston, USA) and Alan Go (Kaiser Permanente Northern California, Oakland, USA) note that the new alternatives to warfarin do not require monitoring and dose adjustment and, in some cases, are more effective and carry a lower risk for intracranial hemorrhage, relative to warfarin.
But they observe that, based on the current findings, "patients who are comfortable with warfarin therapy and whose TTR is above 75% should be in no hurry to switch."
Singer and Go welcome the "new, very promising era" of anticoagulation in AF patients, but note that "warfarin management has also evolved […] likely slowing the ultimate transition to modern anticoagulant agents."
MedWire (www.medwire-news.md) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2012
By Eleanor McDermid