The little boy is doing well a year after the operation, assures heart surgeon Joseph Turek from Duke University Medical Center in North Carolina. The new heart valves worked well and had even grown a bit. The latter is not a given. So far, there are only replacement valves available for babies and children that cannot keep up with the growth of the heart: heart valves from deceased donors from tissue banks that no longer contain any living cells. Once they become too small, they need to be replaced. This is not only a great burden, says Turek, but is also associated with high risks with every operation and an overall risk of death that increases by 15 percent every year.
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The prospects of the little boy, who had severe congenital heart defects, were particularly poor. He didn’t just need two new heart valves. To do this, a hole in the partition between the two halves of the heart had to be closed. Finally, the surgeons had to turn a common outlet vessel on the heart into two separate ones so that the oxygen-rich blood for the body does not mix with the oxygen-poor blood. Turek’s team therefore decided on a new strategy to spare him the follow-up operations.
Heart valves and arteries transplanted
Doctors transplanted two living heart valves from a fresh donor heart from another newborn to the baby when he was 18 days old. “We call it a partial heart transplant,” says Turek. Perhaps a bit exaggerated, especially since they used the same surgical technique that is used to replace dead heart valves, but it is intended to show that it is living tissue. A piece of the adjacent arteries was also transplanted with the flaps, which makes sewing them in easier. The doctors have the case in the specialist journal Journal of the American Medical Association published.
That’s exactly why the little recipient needs a drug that slows down his immune system and prevents it from rejecting the new valves. “Instead of the full dose of two immunosuppressive drugs, we only need half the dose of one,” says Turek. The heart surgeon considers the risk of rejection of the heart valves to be relatively low: “We think that they are quite – what we call immune-privileged -. We don’t think that they cause rejection to the same extent as a whole heart.” Nevertheless, they are necessary. However, you obviously have to find suitable donors in each case.
The heart surgeon hopes that the new heart valves will last a very long time, much longer than whole donor hearts. “If we transplant a new heart into a newborn, it only lasts about 20 years,” says Turek. However, this is due to the heart muscle, which is slowly failing, not to the heart valves, which are still fit. A total of 13 children aged up to three years have been operated on using the new method, nine of them by Turek’s team.
Domino effect with a donor heart
The new method has also opened up the possibility of so-called domino transplants, says the heart surgeon. If a child with severe heart failure needs a new heart, the heart valves are usually still in good condition. They could be donated as soon as the child receives a new donor heart. Sometimes the heart valves went to different recipients, so that a new heart can save two or more lives through the domino effect. It also means that children with life-threatening heart valve defects do not have to wait for a completely healthy new heart.
“The advantage of the new method is that the valves, as living material, can theoretically grow,” says Arjang Ruhparwal, head of the clinic for cardiac, thoracic, transplant and vascular surgery at the Hannover Medical School. “You have to look over the long term to see whether they grow with you. It’s always so ungrateful with heart valves because you only know ten or 20 years later whether what you were thinking about is actually true.”
The main disadvantage, however, is “that you have to suppress the immune system, like with a heart transplant.” Ruhparwal is not convinced that the heart valves with the adjacent piece of vessel have little risk of rejection. “Studies have to show whether this is the case. Basically, a living, foreign heart tissue is implanted and it is rejected in the same way as if a whole heart were taken,” says the heart specialist. It is important to show that the previous cases were not a coincidence.
In fact, Turek’s team is planning a clinical trial with infants who each need a new heart valve. It should run for at least two years and show that the method enables heart valves to grow and that less immunosuppression is sufficient.
(jl)
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