A Bigger Donor Pool for Tiny Hearts
Date: February 28, 2010
Until recently, a physician faced double jeopardy in treating an infant in need of a heart transplant. Not only were there the risks associated with the procedure itself, but there was a 40 percent chance the baby would die because the paucity of infant donor hearts made finding one of a matching blood type extremely difficult.
The odds have now improved. A study by Luca Vricella, chief of pediatric heart and lung transplantation, has confirmed that infants up to 14 months of age can accept a donor heart of a different blood type without increasing the risk of rejection. The reason is that their immature immune systems are producing few if any isohemagglutinins.
Vricella’s experience is more than theoretical. Last summer, an infant was brought to Johns Hopkins in dire need of a transplant. She had been operated on at age 3 days to correct congenital defects, tetralogy of Fallot and pulmonary atresia, but her condition nevertheless worsened, leading to heart failure at 6 weeks that required her to be placed on extra-corporeal membrane oxygenation. A transplant was critical to the infant’s survival, but with no matching donor heart available, Vricella decided to move ahead with an ABO-incompatible organ.
In his study, Vricella had looked at data collected by the United Network for Organ Sharing between 1999 to 2007 involving 591 infants undergoing transplant. Of 556 who received ABO-compatible hearts, two died from transplant rejection. Among 35 ABO-incompatible transplants, there were no deaths. Survival after three years was 75 percent for both groups.
A transplant with an ABO-incompatible organ still requires special precautions, though. “We wipe out the immune system, purge it of any antibodies that may have formed,” says Vricella.
Despite that safeguard and what his study had shown, the outcome with his 6-week-old patient was at first far from certain. “It was a bit nerve-wracking,” he says. “It was being done in a small baby who had just had surgery. She was not the ideal candidate.”
A year later, however, that infant is a playful, laughing baby girl. Equally significant is that she represents an important step forward in infant cardiac care. “The real issue here,” Vricella says, “especially in a state like Maryland where there aren’t a lot of donors, is that our ability to do these operations widens the donor pool.”