Donor organs are exceedingly scarce, so much so that one in five people on the waiting list for a heart transplant in the U.S. dies or is removed from the list before receiving a transplant.
In a new paper published in JAMA, researchers from the University of Chicago, in collaboration with federal policymakers, proposed a new organ allocation policy to address this problem by using a score that prioritizes wait list candidates using objective, laboratory-based measurements of heart failure.
In an analysis of more than 45,000 “match runs” that generate a ranked list of transplant candidates, the new system did a better job of prioritizing the sickest patients for transplant than the current system, which is based on the treatments patients receive.
“Our match run analysis of an actual novel policy is strongly suggestive that if we move from the current system to this policy, we could save even more lives with heart transplant,” said William F. Parker, MD, PhD, Associate Professor of Medicine and Public Health Sciences at UChicago and senior author of the study. “We took a really important step closer to the goal of developing an objective medical urgency score for heart transplant.”
Objective measures over treatment decisions
The proposal uses the U.S. Candidate Risk Score (US-CRS), a new measure first described by Parker and his team in another JAMA paper in 2024. US-CRS is designed to predict the likelihood that a patient will die if they don’t receive a heart transplant within six weeks of being placed on the waiting list. The current heart allocation system uses a six-status model that places patients into different levels of severity based on the treatments they are receiving, such as mechanical circulatory support devices or aortic balloon pumps. Since treatment choices are subjective, this system can be manipulated by putting patients on more aggressive treatments to bump them up to a higher status on the list.
The US-CRS considers treatments, but it also includes clinical and laboratory measurements associated with end-stage heart failure, such as levels of molecules in the blood associated with heart, liver, and kidney failure. The result is a score that better identifies the sickest patients by objective measures.
“The current system provides a natural incentive for well-meaning heart transplant physicians to treat their patients with more aggressive treatments than they might have otherwise, in order to get them higher priority status on the list,” Parker said. The current system also allows physicians to file exceptions requesting higher status for their patients, giving them even more room to negotiate their way up the list.
Making a proposal a practical reality
Collaboration with the Scientific Registry of Transplant Recipients (SRTR), a national database of transplant statistics and analyses under the Health Resources and Services Administration (HRSA), and the policymaking Organ Procurement and Transplant Network (OPTN) heart committee was key to the success of the project. First author Grace Lyden, PhD, an SRTR contract biostatistician, designed improvements to the original US-CRS by including more advanced measures of heart function, more detailed treatment information, and improved methods.
Importantly, the team didn’t just improve a risk score; they developed a new heart allocation algorithm that could be adapted for policy. This algorithm handles other factors, like the distance between the donor and candidate.
“Our proposed policy would both save more lives and reduce the distance that the heart had to travel, which would prioritize sicker candidates and get them a transplant more quickly,” Parker said.
The US-CRS will need to go through many more administrative hurdles, testing, and revision before it can be officially adopted as national heart transplant policy. But Parker said he is encouraged by the progress the team has made refining and proving the new model over the past few years.
“Working directly with key policymakers was good because they gave us critical feedback about making this a practical reality,” Parker said. “My dream would be that we can implement this within a few years, so we lose fewer patients and finally have a more fair system that doesn't depend on arbitrary subjective decision making but instead reflects the true medical urgency of the heart transplant candidates.”
