Revisions to allocation policy did not lower pediatric heart transplant waitlist mortality
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Key takeaways:
- Mortality for pediatric patients on the waitlist for heart transplantation fell from 1999 to 2023.
- The decline was not due to the 2016 revisions in the UNOS pediatric heart transplant allocation policy.
The 2016 revisions to the United Network for Organ Sharing pediatric heart transplant allocation policy were not independently associated with a drop in waitlist mortality, researchers reported.
“The goals of the current allocation system are to improve waitlist mortality and to allocate organs ethically and fairly,” Christopher Almond, MD, professor of pediatrics at Stanford Medicine Children’s Health, said in a press release. “Waitlist mortality has declined, which is a very good thing, but based on our analysis, it doesn’t look like the allocation changes made the difference. Although the intent behind the current system is to prioritize the children based on medical urgency, we saw that the system is not actually sequencing patients according to their risk.”
According to the study background, in 2016, the United Network for Organ Sharing (UNOS) revised its three-tier medical urgency criteria for pediatric heart allocation, with the goal of improving risk differentiation.
Almond and colleagues used data from the Organ Procurement and Transplantation Network to evaluate 12,408 pediatric patients listed for heart transplantation from 1999 to 2023. The patients were stratified by era, with the first era covering 1999 to 2006, the second era covering 2006 to 2016, the period after broader regional sharing of donor hearts was implemented, and the third era covering 2016 to 2023, the period after the revisions to the UNOS allocation policy were made.
During the study period, the rate of waitlist mortality declined from 21% in the first era to 17% in the second era to 13% in the third era (P < .01), the researchers found.
At the time of listing, children from the third era were less sick than children from the first era, with extracorporeal membrane oxygenation use decreasing by 6 percentage points, ventilator use dropping by 11 percentage points and dialysis use declining by 1 percentage point (P < .01 for all), according to the researchers.
Compared with the first era, in the third era, ventricular assist device use increased by 13 percentage points and ABO-incompatible listings rose by 27 percentage points, whereas “nonwhite” patient mortality dropped by 10 percentage points and blood group O infant mortality fell by 13 percentage points (P < .01 for all), Almond and colleagues found.
When the researchers conducted a multivariable analysis, they found that the 2016 allocation policy revisions were not significantly associated with reduced waitlist mortality, but VAD use, ABO-incompatible transplants, improved patient selection and narrowing of racial disparities were.
In match-run analyses, Almond and colleagues found that the correlation between individual waitlist mortality risk and the match-run order was poor.
‘It is really complicated’
“It’s very challenging because if a patient is on full life support and their organs are shutting down, that person is very sick and may not survive the waitlist period. And if you transplanted them, those same risk factors mean they may not have a good outcome with transplant,” Almond said in the release. “It is really complicated to figure out how to do this well, but it appears there is still room for improvement.”
UNOS is expected to propose a new allocation system for donor hearts in 2025, according to the release.
Policy change ‘missed the mark’
In a related editorial, David L.S. Morales, MD, executive co-director of the Heart Institute and director of the division of cardiothoracic surgery at Cincinnati Children’s Hospital and James Scott Tweddell Chair of Congenital Heart Surgery and professor of pediatrics and surgery at the University of Cincinnati, and Benjamin S. Mantell, MD, PhD, pediatric cardiologist at Cincinnati Children’s Hospital and assistant professor of medicine at the University of Cincinnati, wrote that the 2016 “policy change missed the mark in aligning medical urgency with listing status.”
“Although an artificial intelligence system may or may not be many years away, a rank-order continuous listing allocation system using multiple patient- and donor-specific factors to best determine which donor/recipient match results in maximized overall survival (both pre- and post-transplantation survival) would be an improvement over the current three-tier system,” they wrote. “This would be an important first step toward improving survival for all children who need a heart transplant.”
References:
- Heart transplant list doesn’t rank kids by medical need, Stanford Medicine-led study finds. https://med.stanford.edu/news/all-news/2024/08/heart-transplant-pediatrics.html.Published Aug. 5, 2024. Accessed Aug. 5, 2024.
- Morales DLS, et al. J Am Coll Cardiol. 2024;doi:10.1016/j.jacc.2024.06.009.
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