Published: Oct. 2, 2007
Updated: Oct. 3, 2007
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By Duke Medicine News and Communications
DURHAM, NC – Women who might have benefited from the use of an implantable heart monitor following a cardiac arrest were far less likely than men to have one prescribed, according to experts at the Duke University Medical Center.
Researchers looked at the records of more than 236,000 Medicare patients between 1999 and 2005 and found that the vast majority of patients who appeared to be eligible for an implantable cardioverter-defibrillator (ICD) didn't get one. But when ICDs were prescribed, men were two to three times more likely than women to receive them.
An ICD is a three-inch device that constantly monitors heart rhythms and uses electrical shocks to help control erratic rhythms that could cause the heart to stop beating.
"Clinical trials show that ICDs save lives, so the sex difference in treatment rates is worrisome," says lead author Lesley Curtis, a health services researcher and assistant professor in the Duke Clinical Research Institute (DCRI).
The findings appear in the October 3 issue of the Journal of the American Medical Association. A companion paper from Duke researchers in the same issue examines ICD use among patients in a subset of U.S. hospitals involved in the American Heart Association's heart failure quality improvement program, "Get With The Guidelines – Heart Failure," and finds essentially the same thing.
"We don't know why the difference exists, but we do know that this is bad news for women," says senior author Kevin Schulman, M.D., an internist and health policy expert at DCRI.
Earlier studies revealing sex differences in ICD use were conducted before Medicare expanded its coverage for the devices, leaving open the possibility that the difference stemmed from income disparities between men and women. In the current study, the influence of income was reduced, because Medicare pays most of the cost of recommended ICDs.
"We found that the use of ICDs overall increased significantly over the study period, but in each year, the use among women lagged way behind that in men," Curtis says.
In addition, there appears to be a racial disparity. The data show that white men are more likely to get ICDs than black men, and white women are more likely to get them than black women.
The researchers say they do not know why ICD use should differ across sex and racial lines, but Curtis says one reason may be because physicians might perceive men to be at higher risk than women. In addition, she says there may be cultural or religious beliefs that may affect a patient's decision to have an ICD.
Schulman says it is discouraging to find such stark differences. "There is definitely an unconscious bias and there are definitely issues of access, but at the end of the day, I think it is about complexity. Our most vulnerable patients – those who need care the most – don't know how to navigate the system."
The study does have some limitations that may have affected the results. An important part of determining eligibility for ICD implantation in the primary prevention group is the heart's ejection fraction (EF), a measure of the heart's ability to pump. ICDs are recommended for people who have ejection fractions of 30 percent or less, but Curtis says women with heart failure are less likely than men to have low ejection fractions. Medicare records do not include that data, so it is possible that some of the women in the study who did not get an ICD were ineligible on that basis.
The study was funded by grants from the National Institute on Aging and the National Heart, Lung, and Blood Institute.
Study co-authors include Sana Al-Khatib, MD; Adrian Hernandez, MD; Alisa Shea, MPH; and Bradley Hammill, MS, all from the Duke Clinical Research Institute.
Several of the study authors, including Curtis and Schulman, have received financial support from pharmaceutical companies and device manufacturers that create products for heart failure care.