Study: Warfarin Best For Oldest Atrial Fibrillation Patients

Study: Warfarin Best For Oldest Atrial Fibrillation Patients

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 saying.

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