New Assessment Quantifies Risks and Benefits of Warfarin Treatment for Atrial Fibrillation

New Assessment Quantifies Risks and Benefits of Warfarin Treatment for Atrial
Fibrillation
Kaiser Permanente, Mass General Study Finds Benefits Strongest for Oldest
Patients and others at High Stroke Risk

OAKLAND, Calif., Aug. 31 /PRNewswire/ -- Warfarin (an oral anticoagulant)
therapy for patients with atrial fibrillation - the most common type of
significant heart rhythm disorder - appears to be most beneficial for the
oldest patients, for those who have had a prior stroke and for patients with
multiple risk factors for stroke, according to a new study by Kaiser
Permanente and Massachusetts General Hospital researchers. This comparative
effectiveness research study, among the first and largest to quantify
warfarin's net clinical benefit - how much a treatment's potential benefits
outweigh its risks - in the usual clinical care of patients with atrial
fibrillation, appears in the September 1 issue of The Annals of Internal
Medicine.

As part of the ongoing ATRIA (AnTicoagulation and Risk Factors In Atrial
Fibrillation) 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 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. In patients who did and did not take warfarin, the investigators
balanced the reduction in ischemic stroke attributable to treatment against
the increase in intracranial bleeding associated with warfarin. Since
intracranial hemorrhages usually have worse outcomes than ischemic strokes,
bleeding events were given greater weight in the comparison.

While warfarin therapy benefited most atrial fibrillation patients, 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. The benefits of treatment increased dramatically with age,
with no clear benefit in the average patient younger than 65 but a reduction
of more than two strokes per 100 patients in those 85 and older.

Occurring when the upper chambers of the heart quiver instead of contract
smoothly, atrial fibrillation affects more than 2.3 million Americans.
Because the heart rhythm disturbance promotes the formation of blood clots,
which can travel to the brain and block an artery, atrial fibrillation
increases the risk of stroke fivefold. 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 such strokes, but the treatment can be
difficult to control and often leads to hemorrhages. In fact, warfarin is
associated with the most emergency admissions for drug-related adverse
reactions, according to the researchers. Balancing the benefits of warfarin
against its most severe risks is critical to making the best therapeutic
decisions for individual atrial fibrillation patients, explains the study's
senior author Alan S. Go, MD, Director of the Comprehensive Clinical Research
Unit at the Kaiser Permanente Division of Research in Oakland, Calif.

Daniel Singer, MD, of the Massachusetts General Hospital Clinical Epidemiology
Unit, the report's lead author, adds, "This comparative effectiveness study
gives us more information about which atrial fibrillation patients are most
likely to benefit from carefully administered warfarin therapy." He explains
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.

Go explains that Kaiser Permanente physicians in Northern California partner
with pharmacist-run anticoagulation clinics to provide thorough and nimble
administration and careful monitoring of warfarin therapy for atrial
fibrillation patients. This allows for delivery of high-quality
anticoagulation therapy through frequent testing and appropriate dose
adjustment to account for changes in diet, medications and clinical status
that may impact the therapy's narrow therapeutic window.

Singer adds, "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."

Additional researchers on the study are: Yuchiao Chang PhD, and Leila H.
Borowsky, MPH, Massachusetts General Hospital Clinical Epidemiology; Margaret
C. Fang MD, MPH, University of California at San Francisco; and Niela K.
Pomernacki, RD, and Natalia Udaltsova, PhD, Kaiser Permanente Division of
Research.

Funding for the study was provided by the National Institute on Aging, the
National Heart, Lung. Blood Institute and the Eliot B. and Edith C. Shoolman
fund of the Massachusetts General Hospital.

About the Kaiser Permanente Division of Research (http://www.dor.kaiser.org/)
The Kaiser Permanente Division of Research conducts, publishes, and
disseminates epidemiologic and health services research to improve the health
and medical care of Kaiser Permanente members and the society at large. It
seeks to understand the determinants of illness and well-being and to improve
the quality and cost-effectiveness of health care. Currently, DOR's 400-plus
staff is working on more than 250 epidemiological and health services research
projects.

About Kaiser Permanente
Kaiser Permanente is committed to helping shape the future of health care. We
are recognized as one of America's leading health care providers and
not-for-profit health plans. Founded in 1945, our mission is to provide
high-quality, affordable health care services to improve the health of our
members and the communities we serve. We currently serve 8.6 million members
in nine states and the District of Columbia. Care for members and patients is
focused on their total health and guided by their personal physicians,
specialists and team of caregivers. Our expert and caring medical teams are
empowered and supported by industry-leading technology advances and tools for
health promotion, disease prevention, state-of-the art care delivery and
world-class chronic disease management. Kaiser Permanente is dedicated to care
innovations, clinical research, health education and the support of community
health. For more information, go to: www.kp.org/newscenter.

About Massachusetts General Hospital
Massachusetts General Hospital (www.massgeneral.org), established in 1811, is
the original and largest teaching hospital of Harvard Medical School. The MGH
conducts the largest hospital-based research program in the United States,
with an annual research budget of more than $500 million and major research
centers in AIDS, cardiovascular research, cancer, computational and
integrative biology, cutaneous biology, human genetics, medical imaging,
neurodegenerative disorders, regenerative medicine, systems biology,
transplantation biology and photomedicine.

SOURCE Kaiser Permanente

Maureen McInaney of Kaiser Permanente, +1-510-891-3173, McInaney@kp.org; or
Emily Schwartz, +1-415-274-7926, eschwartz@golinharris.com, for Kaiser
Permanente; or Sue McGreevey of Mass. General, +1-617-724-2764,
smcgreevey@partners.org