March 9, 2006
Stroke-prevention drug underutilized in minorities
NEW YORK (Reuters Health) - Despite its proven efficacy in
reducing the risk of stroke in patients with abnormal heart
rhythm, the blood thinner warfarin is less commonly given to
racial minorities, even though their risk of stroke is higher
than that of whites, a new study shows.
Furthermore, only about half of older patients in the
United States hospitalized with abnormal heart rhythm, also
referred to as atrial fibrillation, are prescribed warfarin
when they are discharged, according to a report in the journal
Stroke. Atrial fibrillation increases the risk of blood clot.
By "thinning" the blood, warfarin can prevent the formation of
these clots, which are the most common cause of strokes.
In a second journal paper, researchers found that
physicians often don't prescribe warfarin for patients over the
age of 80 who have atrial fibrillation, even though their risk
of stroke is high. Failure to prescribe the drug is frequently
attributed to other existing conditions that would put the
patient at risk for complications.
Dr. Brian F. Gage, from Washington University School of
Medicine in St. Louis, and his associates created a National
Registry of Atrial Fibrillation II data set. Their analysis
included Medicare beneficiaries (i.e., at least 65 years old)
hospitalized with atrial fibrillation between April 1998 and
March 1999. The study consisted of 16,007 non-Hispanic whites,
797 blacks, and 468 Hispanic subjects.
Warfarin was prescribed for 49.1 percent of patients at
discharge. Even among "ideal candidates" -- those with a high
risk of stroke and few reasons for not receiving the drug --
warfarin was prescribed for only 64.6 percent.
Overall, warfarin was prescribed for 49.7 percent of
whites, 43.2 percent of blacks, and 40.2 percent of Hispanics.
Compared with whites, blacks and Hispanics who were prescribed
warfarin were more likely not to be monitored during the first
90 days (9.7 percent, 21.3 percent and 16.7 percent,
respectively) and at regular interval after 90 days.
Warfarin use was associated with a 35-percent reduction in
strokes, which compares poorly to the 65-percent reduction
observed in clinical trials, the authors note. The drug was
even less effective in preventing stroke among minority
Gage's team suggests that poor follow-up probably
contributes to warfarin's reduced efficacy among blacks and
Hispanics, as well as their increased risk of strokes unrelated
to blood clots (for which warfarin provides less effective
prevention) and their higher risk of diabetes and high blood
To determine the reasons why physicians don't prescribe
warfarin for patients with atrial fibrillation, Dr. Elaine M.
Hylek at Boston University School of Medicine and her
associates followed 405 patients age 65 or older who were
admitted to a hospital for atrial fibrillation between 2001 and
They found that 51 percent of the patients were started on
warfarin: 75 percent of those 65 to 69 years old, 59 percent of
those 70 to 79, 45 percent of those 80 to 89, and 24 percent of
those age 90 or older.
The most common reasons that physicians cited for not
prescribing warfarin were hemorrhage (33 percent), falls (32
percent) and patient refusal or history of nonadherence (14
percent). Other reasons included mental impairment, alcohol
abuse and advanced illness.
Approximately 75 percent of those not prescribed warfarin
were put on aspirin or aspirin plus clopidogrel, which are less
effective than warfarin at preventing stroke.
Strategies are needed to increase treatment eligibility of
elderly patients, particularly reducing the risk of hemorrhage
and falls, Hylek's team maintains. They also call for research
to find alternative stroke prevention strategies that don't
increase hemorrhagic risk.
SOURCE: Stroke, April 2006.