Study: Warfarin Best For Oldest Atrial Fibrillation
Reported September 07, 2009
(Ivanhoe Newswire) -- Elderly patients with multiple risk factors for
stroke benefit most from warfarin therapy for atrial fibrillation – the most
common type of heart rhythm disorder, according to a new study.
Atrial fibrillation occurs when the upper chambers of the heart quiver
instead of contracting smoothly, and promotes the formation of blood clots
that can travel to the brain and block an artery. Atrial fibrillation
increases the risk of stroke fivefold and affects more than 2.3 million
Americans. The condition is highly age-dependent and affects 10 percent of
those over age 80.
Researchers have long known that warfarin is effective in preventing
strokes, but the treatment can be difficult to control and often leads to
hemorrhage. In fact, warfarin is associated with the most emergency
admissions for drug-related adverse reactions. Balancing the benefits of
warfarin against its most severe risks is critical to making the best
therapeutic decisions for individual atrial fibrillation patients, the
study's senior author Alan S. Go, MD, director of the Comprehensive Clinical
Research Unit at the Kaiser Permanente Division of Research, was quoted as
As part of the ongoing ATRIA (AnTicoagulation and Risk Factors In Atrial
Fribrillation) study, researchers followed 13,559 adults with atrial
fibrillation treated within Kaiser Permanente of Northern California from
1996 to 2003. To evaluate the risks and benefits of warfarin treatment and
to give patients and physicians quantitative guidance in making therapeutic
decisions, the researchers analyzed rates of the two most significant
adverse events associated with warfarin therapy – ischemic stroke, the type
produced by arterial blockage, and intracranial hemorrhage, bleeding within
and around the brain.
While warfarin therapy showed no clear benefit in the average patient
younger than 65, the benefits of treatment increased strikingly with age.
Researchers observed a reduction of more than two strokes per 100 patients
in those 85 and older. The balance of benefits over risks was greatest in
those at highest risk of stroke – those with multiple risk factors, those
with a history of stroke and the oldest patients.
Daniel Singer, MD, of the Massachusetts General Hospital Clinical
Epidemiology Unit, the report's lead author, was quoted as saying, "This
comparative effectiveness study gives us more information about which atrial
fibrillation patients are most likely to benefit from carefully administered
warfarin therapy." He explained that by assessing warfarin within a "real
world" practice setting, the study provides a more contemporary assessment
of the therapy's overall effects than do older clinical studies.
Singer added, "One of our distinctive findings is that stroke risk continues
to increase in patients age 85 and older and that warfarin provides
substantial net protection for these elderly patients. A caution is that all
these patients were presumably judged by their physicians to be reasonable
candidates for warfarin therapy, so these results do not automatically apply
to all elderly atrial fibrillation patients."
SOURCE: Annals of Internal Medicine, September 1, 2009