麻豆传媒

NATIONAL HARBOR, Md. -- Four years after a major revision of the U.S. heart transplant allocation rules, deliberations are again underway on how to curb gaming of the United Network for Organ Sharing (UNOS) system.

The recent explosion in Status 2 transplant candidates with advanced heart failure would improbably suggest that "suddenly the entire country has sicker patients," said Shelley Hall, MD, chief of transplant cardiology at Baylor Scott & White Health in Dallas and chair of the cardiac committee for UNOS.

More likely, centers are gaming the system to get their patients faster access to sought-after hearts, Hall suggested during the annual meeting of the Heart Failure Society of America (HFSA).

Instead of patients actually becoming higher-acuity, the crowding of Status 2 is probably related to people getting devices -- intra-aortic balloon pumps (IABPs), for example -- to move to the near top of the transplant waitlist. "Are we putting balloon pumps in less ill patients? I'll leave it there," Hall said.

The balloon pump phenomenon has been observed elsewhere. Fellow panelist Maryjane Farr, MD, of UT Southwestern Medical Center in Dallas, pointed out that, when the U.K. moved IABP patients from urgent to super-urgent priority for hearts, people quickly crowded into this category.

Hall said that work is starting now on changing the UNOS heart allocation system once again, with goals including prioritizing the sickest patients first to reduce waitlist deaths, improving long-term survival after transplant, and increasing opportunities for patients who are medically harder to match. Flexibility, equity, and agility are being stressed as well.

Specifically, one change would be dropping IABP patients down to Status 3 in UNOS.

The U.S. might also take a page from France's allocation playbook, which organizes the heart transplant waitlist by candidate risk score, donor-recipient age-matching, and a transplant risk score combining recipient and donor variables, according to Farr.

Hall suggested that UNOS is considering a points-based ranking system designed to smooth out hard boundaries and improve equity in access. This would take the form of a composite score that weighs medical urgency, post-transplant survival, candidate biology, patient access, and placement efficiency.

A preliminary proposal is slated to be released by the end of 2023 and a final version of the new framework is projected for the year 2027, she announced.

The maxim that "it takes 10 years to create new policy" just won't cut it for the transplant community, Hall emphasized to the HFSA audience. "We're not going to be able to survive 7, 8 years with our Status 2s."

UNOS currently places patients supported with veno-arterial extracorporeal membrane oxygenation (VA-ECMO) or surgically implanted, non-dischargeable mechanical circulatory support (MCS) devices at Status 1, the highest priority for a heart transplant, whereas those with IABP or percutaneous MCS are right behind them in Status 2.

The current six-tier system, implemented in 2018, was itself created in response to a historical excess of patients meeting top-priority Status 1A criteria for a heart transplant, making it difficult to organize the list within that highest tier.

That change reduced the waitlist time to transplant from a median 226 days to 85 days nationwide, accompanied by a trend for improved waitlist survival overall, according to Hall.

Nevertheless, the additions to the waitlist continue to outpace the number of hearts available. So far in 2022, there have been at least 3,531 people placed on the list versus 2,826 hearts transplanted, according to HFSA session discussant Gregory Ewald, MD, of Washington University School of Medicine in St. Louis.

"The delta keeps growing every year," he lamented.

Indeed, "with a finite resource of donors and an ever-increasing list of candidates, allocation systems merely rearrange the line order but never [shorten] the line," Hall said.

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