Children who are born with heart valve defects often undergo surgery to receive frozen valves from cadavers. Because thawed cadaver tissue is dead and doesn’t grow, however, the child must periodically have operations to get larger valves—which can lead to a poor prognosis. But in a new procedure known as a partial heart transplant, living valves and parts of blood vessels can be transplanted and grow along with a child.
In 2022 a newborn named Owen Monroe became the first infant to receive such a transplant from a brain-dead newborn donor. Owen was born with a rare condition called truncus arteriosus: he had only one blood vessel coming out of his heart and one corresponding “truncal” valve, instead of the usual two. This defect causes oxygen rich and oxygen-poor blood to mix, which in turn makes blood pool in the lungs and requires the heart to work harder. Plus, Owen’s existing truncal valve was too leaky for him to survive with. Doctors replaced the valve (and associated blood vessel) with part of a donor aorta and valve, as well as part of a pulmonary artery and valve.
Owen’s transplant was functioning well a year after the procedure, according to a new report in JAMA from Joseph W. Turek, chief of pediatric cardiac surgery at Duke Health, and his colleagues. “As he grows, the valves are proportionately growing. The valves function perfectly,”says Turek, who performed the surgery, adding that Owen is “meeting all of his milestones.” They also found that Owen had not suffered any immune rejection.
Like any transplant recipient, Owen receives medications that prevent his immune system from rejecting the foreign tissue. But these drugs have risks, so Turek and his colleagues aimed to use the lowest dose possible. Around Owen’s first birthday, they were able to reduce his medications to just one—at half the initial dose. “Immunosuppressing a kid is not without risk,” says Jennie Kwon, a resident in cardiac surgery at the Medical University of South Carolina, who conducted some of the research that led to the new study. But given that these valves don’t have much blood supply, researchers hope immune cells can’t get to them as easily—meaning recipients won’t need as much immunosuppression. “Just to get a year out [with the transplanted valves], I think, is a great win,” Kwon says.
A dozen such transplants have since been performed in the U.S., Turek says. Last May doctors at NewYork-Presbyterian Morgan Stanley Children’s Hospital performed the first “domino” partial heart transplant in infants: they transplanted a complete donor heart into one baby who needed a new heart muscle and then immediately transplanted that baby’s original heart valves into another infant, saving two lives at once.
“This is the first study that shows that the valves are at least growing, which is huge,” says Andrew B. Goldstone, a pediatric heart surgeon who helped to perform the domino transplant. But he cautions that it’s “still very early days.”
The biggest remaining challenges, Goldstone and others say, are logistical and regulatory. There’s currently no established system for matching valve donors and recipients or for monitoring how well recipients do afterward. But Turek hopes that the procedure will ultimately benefit many more children. “I look at it as wonderful stewardship of precious organs,” he says. “We’re just trying to help as many babies as we can.”