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UNOS considering new US adult heart allocation system
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The heart subcommittee of the United Network for Organ Sharing is in the process of proposing a six-tier system that would replace the current three-tier system used for allocating hearts to adults in the United States who need transplantation.
The proposed system aims to reduce wait-list mortality without decreasing posttransplant survival, Dan M. Meyer, MD, former chairman of the UNOS heart subcommittee and an author of the proposal published in the American Journal of Transplantation, told Cardiology Today.
Dan M. Meyer
“While there were very positive results from previous interventions to change the system, [UNOS] did notice that the waiting-list mortality in the highest acuity statis, Status 1A, was still higher than optimal,” said Meyer, surgical director of mechanical circulatory support at Scripps Health in La Jolla, Calif., and professor of thoracic and cardiovascular surgery at the University of Texas Southwestern Medical Center in Dallas.
In the current system, patients awaiting a heart transplant are classified into one of three tiers: status 1A, for those with highly acute conditions; status 1B, for those with moderately acute conditions; and status 2, for those with stable HF, Meyer said.
The proposed system includes six tiers that better stratify patients by how sick they are, Meyer said.
- Tier 1: patients with extracorporeal membrane oxygenation, mechanical ventilation, a nondischargeable ventricular assist device (VAD) or mechanical circulatory support with life-threatening ventricular arrhythmia;
- Tier 2: patients with an intra-aortic balloon pump, ventricular tachycardia or ventricular fibrillation without mechanical support, mechanical circulatory support with a device malfunction or mechanical failure, a total artificial heart or a dischargeable biventricular VAD or right VAD;
- Tier 3: patients with an LVAD for up to 30 days; a Status 1A exception under the current system; multiple inotropes or single high-dose inotropes with continuous hemodynamic monitoring; or mechanical circulatory support with device-related complications not included in Tier 1 or Tier 2;
- Tier 4: patients diagnosed with certain kinds of congenital heart disease, ischemic heart disease with intractable angina, hypertrophic cardiomyopathy or amyloidosis; those stable on an LVAD after 30 days; inotropes without hemodynamic monitoring; those requiring a retransplant; and those with a Status 1B exception under the current system;
- Tier 5: patients approved for a heart-lung, heart-liver or heart-kidney transplant; and
- Tier 6: all remaining active candidates; equivalent to status 2 in the current system.
“The issue [with the current system] is that once a patient is listed as 1A, they are on the list, and any other 1A candidate that is listed is behind that patient. It is urgency-based but it also reflects time on the waiting list,” Meyer said. “As more and more patients are getting 1A status, it’s really whoever is 1A first, within the blood group and weight range, is going to get the organ first, no matter if you have a patient that is stable with an LVAD for 30 days, or if you have a patient [requiring extracorporeal membrane oxygenation]. We want to make it so the highest acuity patients are getting the organs.” He noted that since 2005, the number of patients listed as status 1A and status 1B has tripled, as more patients with HF have survived longer because of advances in medical management and mechanical support.
Another goal was to better address patients who had status 1A and 1B exceptions under the current system, according to Meyer. “These are patients with ventricular arrhythmias, congenital heart disease, different cardiomyopathies and [other conditions] that are not represented adequately in the system or disenfranchised,” he said. “They weren’t getting an opportunity to get a higher allocation status. Finally, the modified allocation proposal will also model different options for improved zonal or geographic sharing of donor organs.”
The proposed system has undergone testing in a thoracic simulation allocation model, which showed that compared with the current system, it decreased waiting-list mortality and did not affect posttransplant survival, Meyer said.
After further fine-tuning, the proposal will go out for public comment, likely in June, and then the UNOS thoracic committee will decide what changes to make based on those comments and whether it should be released for public comment again. Once all changes are incorporated, the proposal will be sent to the UNOS board for final approval and changes will have to be made to information technology systems to reflect the new scheme, he said. It will likely take 18 to 24 months before the new system is implemented.
The proposal does not include a heart allocation score, but one might be developed in the future, according to Meyer. “Part of that process involves prospective collection of important data elements,” he said, noting that a well-designed allocation score “can really ensure that the highest-acuity patients and the patients that benefit most from transplant will be getting the organs.” – by Erik Swain
For more information:
Dan M. Meyer, MD, can be reached at Scripps Cardiovascular and Thoracic Surgery, 9850 Genesee Ave., Suite 560, La Jolla, CA 92037; email: meyer.dan@scrippshealth.org.
Disclosure: Meyer reports no relevant financial disclosures.
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