AHA 2008: Gender-Matched Heart Transplants Lead to Better Survival

Shelley Wood

November 21, 2008

November 21, 2008 (New Orleans) — In the largest study to date looking at the issue, researchers report that survival in heart-transplant recipients is significantly reduced if recipients receive a heart from a donor of the opposite sex.

According to Dr Eric Weiss (Johns Hopkins Medical Institutions, Baltimore, MD), who presented the analysis during the American Heart Association 2008 Scientific Sessions, the findings should help transplant programs choose the best recipient for a heart transplant when a donor organ becomes available.

In an interview with heartwire , Weiss explained that gender matching has been explored in other solid-organ transplants and even in the setting of heart transplantation, but in small numbers, typically at single-center institutions. For his study, Weiss and colleagues used the United Network for Organ Sharing, containing information on more than 18 000 heart-transplant recipients who underwent transplantation between 1998 and 2007.

They found that 77% of men and 51% of women had actually been matched by gender to their donor and that gender-matching was associated with a 15% reduction in adjusted, all-cause, cumulative mortality. Patients at greatest risk of dying over the study follow-up were women who had received hearts from male donors, a statistically significant 23% increased risk as compared with men who received hearts from male donors, followed by males who received hearts from female donors, a 15% increased risk. By far, male recipients of male hearts had the lowest mortality out to nine years--61%, as compared with 54% in women who'd received a heart from a male donor, a statistically significant difference (p<0.001 by log rank test).

In secondary analyses, the authors also looked at gender mismatch and transplant rejection and found that gender mismatch was associated with organ rejection only in men who'd received hearts from female donors. In fact, female recipient gender in itself was a risk factor for rejection, regardless of the sex of the donor.

According to Weiss, gender is already taken into account during donor-recipient selection, in part due to the size of the chest cavity. Many women, for example, cannot physically accommodate a larger (male) heart due to the constraints placed by the chest wall. Physiologically, he added, sex matters in terms of functional capacity. "The heart needs to have the functional reserve, the beating power, to pump to a large body," Weiss explained.

Other factors include the minor histocompatibility antigen on the Y chromosome, believed to be an important cause of transplant rejection, and what Weiss called the "hormonal milieu," which appears to confer benefit when the donor and recipient are of the same gender. But overall, he said, the reasons underpinning gender-matching are incompletely understood and were not something that could be probed in any depth in the current study.

"With these multi-institutional databases, it's a little hard, because we are at the mercy of the variables that individual institutions have collected," Weiss said. "So this study would have been designed a bit differently if we had been collecting the variables ourselves."

According to Weiss, the current study is part of an ongoing effort to create a risk score for predicting patient outcomes. "Our focus is on understanding factors that lead to improved outcomes after heart transplantation. This is one factor, and clearly there are other factors--as we learn more about this we can improve our ability to match donors and recipients."

He emphasized that patients who have received a heart from someone of the opposite sex or physicians with patients whose hearts are "gender mismatched" should not be overly concerned. "We don't want people to think that this somehow means they're going to have a poor outcome. It still is muchbetter to receive a transplant than to live with end-stage heart failure, even if you have a mismatched organ, especially if the organ is matched in a lot of other ways, from a [human leukocyte antigen] standpoint or an age standpoint--that kind of thing."

But he also emphasized that the information could help guide decision-making, particularly since the number of patients needing heart transplantation far exceeds the number of donor organs. "If all else is equal and you're trying to decide which recipient should get a heart, it would probably be better to take a donor of the same sex," he said.

Weiss disclosed having no conflicts of interest.

The complete contents of Heartwire , a professional news service of WebMD, can be found at www.theheart.org, a Web site for cardiovascular healthcare professionals.


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