The world's first partial heart transplant has achieved what researchers have hoped for more than a year: functioning valves and arteries that grow with the young patient, as hypothesized by the pioneering team behind the procedure at Duke Health.
A study conducted by doctors at Duke Health found that the new way of obtaining valves used during the transplant of partial heart resulted in two well-functioning valves and arteries that are growing in concert with the baby as if they were native vessels.
The results of research were published in the Journal of the American Medical Association.
First partial heart transplant: here's how it was possible
The first partial heart transplant procedure was performed in spring 2022, in a newborn baby who needed heart valve replacement. The previous standard of care, which used nonliving valves, would not grow with the baby, requiring frequent replacements and involving surgical procedures that carry a 50 percent mortality rate.
“This publication is proof that this technology works, this idea works, and it can be used to help other children,” said Joseph W. Turek, M.D., Ph.D., first author of the study and chief of pediatric cardiac surgery at Duke, who conducted the basic procedure.
The study also found that the partial heart transplant procedure requires about a quarter of the amount of immunosuppressant drugs as a full heart transplant, potentially sparing patients from harmful side effects that could worsen over decades.
Turek said the innovation paved the way for domino heart transplantation, in which one heart can save two lives. During a domino heart transplant, a patient who has healthy valves but needs a stronger heart muscle receives a complete heart transplant; their healthy valves are then donated to another patient in need, creating a domino effect.
“It could potentially double the number of hearts used to benefit children with heart disease,” Turek said. “Of all donated hearts, about half meet the criteria to be used for complete transplantation, but we believe there are an equal number of hearts that could be used for valves.”
“If you introduce donated hearts that have not been used into the supply chain and add valves from domino heart transplants, that can create a substantial change,” Turek said.
The partial heart transplant procedure has been performed 13 times at four centers worldwide, including nine at Duke, many of which were domino heart transplants.
Turek said bringing this innovation into a clinical trial would be the next step in achieving the volume of procedures that would dramatically change the availability of hearts.
“This innovation adds so much to the entire donation community,” Turek said, “because it allows more children to be treated while honoring the wishes of the altruistic donor parents who made the ultimate gift. It allows them to offer hope to another child in the process.”
The partial heart transplant procedure had only been performed on pigs, doctors said. During an eight-hour surgery in April 2022, surgeons at Duke University fused living arteries and valves from a donor heart to a human heart for the first time, potentially creating a new field of cardiac surgery.
“I think this is really one of the most profound developments in pediatric heart surgery in a long, long time,” said Dr. Joseph Turek, who led the partial heart transplant surgery: “This will really change the way children they will be taken care of in the future.”
Owen Monroe, the tiny patient who underwent a partial heart transplant, was born with an extremely rare condition that fuses the two main arteries of the heart together. On top of that, the valve he had lost badly, allowing blood to pool in his heart.
“It's like winning the unlucky lottery,” Nick Monroe said. Doctors initially presented Owen's parents with two options.
The first was to replace the entire heart, which could have required up to six months of waiting to find a donor organ. In all likelihood, Owen would have died before a heart was available, said Turek, chief of pediatric cardiac surgery at Duke.
The second option was to use tissue from a cadaver to repair its heart, an extremely risky procedure for children with leaky valves.
Even if this were successful, the dead tissue would not grow with the rest of the heart, and Owen would have to undergo numerous other heart operations over the course of his life, each riskier than the last.
Neither option seemed likely to save her son's life, doctors said. The situation became so complicated that the baby's parents began to consider whether Owen, who was less than a week old, was destined to become an organ donor for another child.
Then they heard about the experimental partial heart transplant surgery: “Necessity is truly the mother of invention,” said Dr. Michael Carboni, a pediatric transplant cardiologist.
One of the most challenging aspects of performing heart surgery on a child is that he and his heart eventually grow: “When their valves need to be replaced or their arteries need to be replaced, we need those arteries and valves grow together with them,” Turek said.
Before now, heart surgeons could replace the organ entirely and condemn the patient to a lifetime of anti-rejection drugs or frequently replace pieces to fit the growing heart, subjecting patients to numerous open-heart surgeries.
Partial heart transplant promises to combine the benefits of each approach. Unlike patients with a completely new heart, patients with a small amount of donor tissue may not have to take as many anti-rejection drugs, which puts them at risk for other diseases because the drugs suppress their immune systems.
Unlike the dead valve tissue that is typically implanted, the live valves used in partial heart transplant can grow with the child's heart, hopefully eliminating the need for future surgery.
Partial heart transplant can allow doctors to tap into a reserve of donor hearts that remain unused due to shortages. Carboni estimates that about half of donated hearts fall into this category.
The organ used in Owen's surgery, for example, had been set aside because the heart muscle was too weak. The valves, however, were completely intact. That could have huge implications for the nearly a quarter of children on the waiting list for heart donors who die before receiving an organ, Carboni said.
There are unknowns about partial heart transplants that doctors are trying to understand. They don't know how many anti-rejection drugs Owen will need or whether he will eventually be able to wean them off altogether. Turek said he hopes to carry out clinical trials on patients who undergo the surgery in the future to understand it better.
“The intellectual part of me wants to say that this is a whole new world and we're entering an exciting new arena and all that stuff,” Carboni said. “The real person inside me says I don't know what the hell I'm doing and I hope I can do what's best for Owen down the road.”
But so far everything has gone well. Owen Monroe, at home with his parents in Brunswick County, is no longer in the midst of a medical emergency. Just like a normal five-month-old, he holds his head high, rolls over and has begun to venture into the realm of solid foods, Tayler said.
Echocardiograms showed that the implanted valves were growing along with the rest of the heart, as hoped. The thin scar along his sternum has begun to fade. “If you met him on the street, you would have no idea anything happened,” Tayler said.
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