Warfarin is safe and effective as a preventive against stroke in patients with atrial fibrillation
Warfarin is safe and effective as a preventive
against stroke in patients with atrial fibrillation, according to
an article in the November 26th issue of The Journal of the American
Medical Association.
According to background information in the
article, multiple randomized clinical trials have demonstrated warfarin
to be highly effective in reducing the risk of ischemic stroke in
patients with atrial fibrillation with relatively low rates of bleeding.
However, concerns persist about the effectiveness and safety of
warfarin use in typical clinical settings because the randomized
trials enrolled highly selected patients, included few very elderly
people, and closely monitored patients' level of anticoagulation.
In the current study, Alan S.Go, M.D., and
his American colleagues evaluated the effect of warfarin on risk
of thromboembolism, hemorrhage, and death in patients with atrial
fibrillation within a usual care setting. The study was conducted
between July 1, 1996, and December 31, 1997, with follow-up through
August 31, 1999, in one large integrated-health care system. A total
of 11,526 adults were included in the study (women, 43 percent;
average age, 71 years). None of the participants had atrial fibrillation
associated with a valvular condition.
Among 11,526 patients, 397 thromboembolic
events occurred (372 ischemic strokes). Warfarin therapy was associated
with a 51 percent lower risk of thromboembolism and stroke compared
with no warfarin therapy (either no antithrombotic therapy or aspirin)
after adjustment for potential confounders and likelihood of receiving
warfarin.
"Warfarin was effective in reducing thromboembolic
risk in the presence or absence of risk factors for stroke,"
the authors wrote. An "analysis estimated a 64 percent reduction
in odds of thromboembolism with warfarin compared with no antithrombotic
therapy. Warfarin was also associated with a reduced risk of all-cause
mortality [death, 31 percent lower risk]. Intracranial hemorrhage
was uncommon, but the rate was moderately higher among those taking
warfarin versus those not taking warfarin. However, warfarin therapy
was not associated with an increased adjusted risk of nonintracranial
major hemorrhage."
"Our results materially extend ... prior
findings by providing contemporary and precise estimates of thromboembolism
and hemorrhage rates in a broad population of individuals with atrial
fibrillation, along with more complete adjustment for potential
confounders and attempts to control for the likelihood of receiving
warfarin over time," they added.
"Overall, our results demonstrate
that findings of the randomized trials of anticoagulation for atrial
fibrillation translate well into clinical practice. Our study adds
further support for the routine use of anticoagulation for eligible
patients with atrial fibrillation who are at moderate to high risk
for stroke, particularly when well-organized management of anticoagulation
can be provided," the researchers concluded.
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