Owen Monroe's heart was born sick. The little boy suffered from a very complex heart disease, very rare; If he was not repaired urgently, he was doomed to death. The large arteries of his heart, the aorta and the pulmonary arteries, they were fused and it barely had one valve (in healthy hearts, there are two, one for each vessel) to control the flow of blood. Time was against her, her heart was suffering every moment and her doctors at Duke University Hospital (North Carolina, USA) were studying all the options against the clock. They even included him on the list for a heart transplant, although they suspected that he would not arrive in time: he had just been born and already had severe respiratory failure that put his future in jeopardy. “Every day seemed to last an eternity. With each passing day you could feel that the wait was weighing on all the ICU staff. It was tense for everyone to have to wait day after day without news knowing that Owen was slowly dying,” recalls Tayler Monroe, the little boy's mother.
The traditional solution in cases of newborns with irreparable heart valve dysfunction is usually to replace the failures with artificial valve implants or from cadaver donors, but these tissues have a drawback: since they are inert grafts, they do not grow with the patient; and as the child develops, they have to be changed through new surgeries to adapt them to the size of the heart. In Owen's case, however, his doctors wanted to try a pioneering technique: a partial heart transplant, the first in the world, to implant living tissue in order to avoid successive operations to replace his valves. The family approved this novel approach and in the spring of 2022, when she was barely 18 days old, surgeons transplanted a part of a donor heart into the baby to reconstruct the affected vessels and valves. The intervention was a success. So much so that a study by his doctors published in the magazine Jamafrom the American Medical Association, reveals that his heart is working correctly and the implanted tissue grows with him, just as the doctors expected.
However, in Owen's case, it was already detected in prenatal check-ups that there were problems in the embryonic development of these large arteries of the heart: “Owen had a rare congenital heart defect called truncus arteriosus. Instead of having two arteries and valves coming out of the heart, he only had one, and that valve leaked terribly. We knew this from prenatal ultrasounds before he was born, so we were able to prepare for this innovative procedure before he was born,” explains Joseph Turek, chief of pediatric cardiac surgery at Duke and one of the architects of the partial heart transplant. .
The medical team knew that the traditional approach, with the replacement of valves through artificial grafts or from a cadaver donor, was not free of additional risks and inevitably led patients to more future interventions because the tissue was not going to grow. “Traditionally, there is an initial mortality of 50% with this approach and an additional mortality of 15% each year thereafter, due to the need for numerous risky operations to replace these non-growing valves,” Turek explains. So they decided to try a new alternative that emerged from their own clinical experience with heart transplants, the doctor says by email. ”The valves and arteries grow when we perform whole heart transplants, so why wouldn't just the valves and arteries grow if they are obtained from a donor and the recipient patient receives some level of anti-rejection medications?” . And they launched into it.
With the family's approval and as soon as they had an organ available from a donor and suitable for this type of case – Turek clarifies that it must be a heart that is not suitable for a complete transplant – they implanted a part in Owen. “This involved sewing both the new aorta (with the aortic valve) and the pulmonary artery (with the pulmonary valve). We also had to reimplant the coronary arteries into the new aorta and close the hole between the pumping chambers of the heart,” explains the doctor.
Outside the operating room, the wait seemed endless for Tayler and Nick Monroe, the little boy's parents. “It was the longest nine hours of our lives. We tried to eat pizza, but we couldn't. We were just sitting there looking at the clock in the hall [del hospital]”, says the mother by email. Every hour or half an hour, yes, they received a call from the operating room nurse to inform them how the operation was going and, around midnight, the doctors confirmed that everything had gone well.
The intervention was a success and a month after the surgery, the child left the hospital in the arms of his parents. Subsequent follow-up for more than a year proved that, indeed, these transplanted arteries and valves worked perfectly and, furthermore, grew as if they were Owen's own. “This is the first demonstration that a valve implant can grow in a human being. “This solves a number of problems we face in children who need tissues that grow with them and can save countless risky reoperations in these babies and children,” defends the Duke cardiac surgeon and author of the study published in Jama.
Valves for life
In the absence of broader studies over time on the evolution of Owen and other children with a partial heart transplant, the researchers theorize that, although the long-term results of a complete heart transplant are limited and the organ ends up failing —”[los resultados] are limited by inevitable ventricular dysfunction,” they say in the article—“partial heart transplants spare the native ventricles and, therefore, are expected to last a lifetime.”
Carlos Velasco, cardiovascular surgeon at the University Hospital Complex of A Coruña (CHUAC), points out that this therapeutic approach “is of interest” in a specific situation: in case the donor organ is discarded because it is not valid for a complete transplant. “The transplant of neonates is an absolute rarity, it is very difficult to transplant them because there are no organs. So, when you have obtained an organ that does not work, but the valves do work, it is interesting that you can have part of an organ that otherwise would not be used,” explains Velasco.
Turek confirms that, indeed, in Owen's case, “the heart [del donante] “He was not suitable for a full heart transplant.” “We do not use hearts from the entire waiting list for heart transplants. First of all, these hearts should be considered unsuitable for a full heart transplant,” agrees the American doctor. Of all the hearts that are donated, the doctor estimates, only half meet the criteria to be used for a complete transplant, but the other 50% could potentially be used to take advantage of the valves, he says.
13 partial heart transplants have already been performed in the world, nine of them at Duke Children's Hospital
Velasco, who has not participated in the study, also believes that using an optimal heart from a donor to use only the valves would make sense, in any case, “if immunosuppressants did not have to be given” to the patient. These drugs, which are administered to transplant recipients to prevent the recipient's body from rejecting an organ received, also have their long-term risks, warns the CHUAC cardiac surgeon: “There is a risk of neoplasms [cáncer] derived from immunosuppression and also infections.”< /p>
Turek limits his technique to a very specific patient profile and defends that the doses of immunosuppressants are lower: “Most complete heart transplants are necessary because the heart muscle does not function well. Partial heart transplant is for patients with valve problems. Fortunately, the amount of immunosuppression needed in these cases appears to be only a quarter of that used in whole heart transplants. “This is a non-life-altering dose.”
For his part, cardiologist Ferran Gran, pediatric heart transplant coordinator at the Vall d'Hebron Hospital in Barcelona, considers this new therapeutic approach “very novel, interesting and promising.” “It is novel because in these pathologies, when denatured valves are inserted, they tend to malfunction and do not grow: the child grows and the graft does not. And this means that you have to reoperate many times. Theoretically—and this is what is being seen for now—this can greatly extend the life of the graft,” celebrates the cardiologist, who has not participated in the research either. Gran also considers that this technique “is a better alternative than what was available” and adds that it would even “be applicable to other patients with less serious pathologies.”
Domino partial heart transplant
By Turek's calculations, 13 partial heart transplants have already been performed in the world, nine of them at Duke Children's Hospital. The doctor also defends that this technique “has opened several more doors to maximize donations to help children in need.” He refers to two new approaches in transplant dynamics: the so-called domino partial heart transplants and split root partial heart transplants.
With them, a single organ can end up saving two lives. “In domino partial heart transplant, there is a child who receives a complete heart transplant. So what happens to that boy's old heart? It is generally discarded. However, if you allow the patient to donate his old heart when it is removed, the valves usually work well. These valves can then be used in another child as a partial heart transplant. To date, five of these domino-shaped partial heart transplants have been performed, three of them here at Duke. For partial split root heart transplants, a donor heart has two valves leading from the heart (aortic and pulmonary). If you split these two roots, you can perform a partial heart transplant on two different children who only need one valve each. One heart helps two children! Two of these types of cases have been done at Duke,” explains Turek.
A few months after two years of the pioneering operation, Owen's heart beats strong and vigorous. “It's very nice! He has some developmental delays that are common in cardiac babies, but he walks and can feed himself. He likes to investigate everything, opening and closing doors… He really loves his second chance at life,” the mother celebrates. The little boy left the hospital with 17 drugs a day, but now he only takes two and does not require special care. He's just “a normal kid on some medication,” Monroe says. She adds: “With traditional trunk repair, Owen would have already had three open-heart surgeries to change the valves as he grew, but he won't have any for the rest of his life if all goes well. ”.
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