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Severity of diabetes is key determinant of heart transplant success

November 07, 2006

Having diabetes should not automatically disqualify you from being considered for a heart transplant, according to a study published in Circulation: Journal of the American Heart Association.

During a 10-year period, heart transplant recipients with uncomplicated diabetes lived just as long as non-diabetic recipients, according to data from the United Network for Organ Sharing (UNOS), a national organization that coordinates transplant organ procurement and distribution. However, heart recipients with severe diabetes-related organ damage, such as a history of kidney disease or stroke, had significantly worse long-term survival compared to recipients without diabetes.

Previous studies examining the impact of diabetes on survival after heart transplantation involved relatively few patients who were followed for a fairly short period. In addition, these studies failed to consider that some people have more severe forms of diabetes than others. Therefore, the impact of diabetes on survival after heart transplantation remained controversial. While no national transplantation rules disqualify people with diabetes from receiving donor hearts, each transplantation center has its own rules, and some centers exclude people with diabetes.

Diabetes significantly increases the risk of heart disease, which is the leading cause of death among people with diabetes. Diabetics are also twice as likely to develop heart failure as those without diabetes.

"The question is not whether a person has diabetes but how much damage the diabetes has done," said Mark Russo, M.D., M.S., one of the study's authors and a researcher at Columbia University's International Center for Health Outcomes and Innovation Research in New York and a postdoctoral residency fellow in surgery at New York-Presbyterian Hospital/Columbia University Medical Center. "A person should not be disqualified from transplantation solely because of diabetes."

Russo and his co-authors examined post-transplant survival in more than 20,000 people aged 18 years and older (average age 52) who received heart transplants between 1995 and 2005, including 3,687 people who were diabetic at the time of transplantation. Because all patients undergoing heart transplantation in the United States during this period were included in the UNOS database, the study offers a nationwide perspective on the issue of diabetes and heart transplantation.

Researchers assessed the severity of the patients's diabetes by their number of diabetes-related complications. Complications were defined as stroke, kidney failure, peripheral vascular disease (diseased blood vessels in the extremities) and severe obesity (body mass index ¡Ã35). The majority (76.1 percent) of the diabetics did not have diabetes-related organ damage.

Transplant recipients with uncomplicated diabetes had a median survival of 9.3 years, which was not significantly different from recipients without diabetes who had a median survival of 10.1 years.

The presence of complications related to diabetes prior to transplantation, however, was associated with worse post-transplant survival in diabetic transplant recipients. The median survival of diabetic recipients with one complicating condition was 6.7 years, while median survival was almost half that (3.6 years) when diabetes was combined with two or more complications. Furthermore, the risk of post-transplant complications increased significantly with increasing severity of diabetes.

It is currently estimated that 60,000 people in the United States could benefit from heart replacement therapies. Median survival following heart transplantation exceeds 10 years, and many recipients live 20 years or more after receiving a transplant. However, due to a critical shortage of donor organs, fewer than 2,500 people undergo this procedure in any given year. Therefore the findings in this study have important implications for the allocation of hearts available for transplantation.

"Many patients with end-stage heart failure, even those with severe diabetes, will live longer after heart transplantation," said the study's senior author, Yoshifumi Naka, M.D., Ph.D., director of Cardiac Transplantation at New York-Presbyterian Hospital and the Herbert Irving Assistant Professor of Surgery at Columbia University College of Physicians and Surgeons.

He emphasized, however, that given the limited number of organs available, it is important to understand the risks and benefits associated with various groups of patients; this will enable the benefits from these limited resources to be maximized. "In the pre-transplant screening, we must identify diabetic patients who have severe end-organ damage," Naka said. "Those patients do not do as well after transplantation; so we must consider alternative treatment strategies for these patients. However, diabetics with only minimal damage should be considered for transplant."

For patients with severe heart failure and severe diabetes, alternatives to transplantation include the use of left ventricular assist devices, small electrical pumps placed in the heart, or the use of "alternative" wait lists for high-risk heart transplant candidates.

Columbia University Medical Center