Donor organs are an absolutely scarce healthcare resource. Below are the numbers of American patients currently on waitlists for organ transplants.
(Obtained from the Organ Procurement and Transplantation Network, 2024)
Heart
Lung
Kidney
Liver
Therapy-based heart allocation system undermines the ability of the system to save lives
Heart transplantation is the definitive treatment for end-stage heart failure, but the demand for donor hearts far exceeds the supply.
The current heart transplant candidate priority ranking system is based on treatment intensity rather than on objective markers of illness severity. Our work using the national Scientific Registry of Transplant Recipients (SRTR) database shows that some transplant centers systematically over-treat candidates to increase their waitlist priority for transplantation (Parker et al., 2019).
Our analyses revealed a significant association between the transplant center of listing and the survival benefit of transplant (Parker et al., 2019):
- High benefit centers save more lives by using the allocation system as intended (i.e., reserving intensive supportive therapies for the sickest candidates, who have the highest survival benefit from transplantation).
- Low benefit centers tend to escalate treatments for more medically stable candidates, transplanting relatively stable patients who could have survived longer on the waitlist.
These results suggest that the current therapy-based heart allocation policy does not meet federal requirements to make the best use of donor hearts by ranking candidates from “most to least medically urgent” (Parker et al., 2019). An improved heart allocation system is needed.
Relationship Between Candidate Survival on the Waiting List, Posttransplant Outcomes, and the Benefit of Heart Transplant for Each US Heart Transplant Center (Parker et al., 2019)
We found a significant association between the status-adjusted medical urgency of candidates listed by each center (as measured by the risk of death on the waiting list) and the benefit of transplant measured by 5-year survival benefit (panel A). For every 10% decrease in expected candidate waiting list survival, there was an increase of 6.2% (95% CI, 5.2% to 7.3%) in estimated survival benefit associated with heart transplant. In contrast, there was no significant association between survival after transplant and center survival benefit (survival difference, 1.5% [95% CI, −3.8% to 0.83%]) (panel B).
In 2016, the OPTN Thoracic Committee recognized the U.S. heart allocation system was not making best use of donor hearts by ranking candidates from “most to least medically urgent”.
- The sickest patients were not prioritized for heart transplantation.
- In 2017, prevalent use of high-dose inotrope and continuous-flow left ventricular assist device (LVAD) therapies placed most waiting adult heart transplant candidates in status 1A, which was intended for critically ill candidates. This increased wait times and variation of candidate illness severity.
- OPTN updated the US heart allocation system in October 2018.
- Status levels were increased from 3 to 6, and top priority was restricted to candidates in cardiogenic shock.
Trends in Treatments Used to List Adult Heart Transplant Candidates During the Transition to the New Heart Allocation Policy (Parker et al., 2020a).
Trends in number of adult heart transplant candidates listed in each month, stratified by treatment at initial listing. Colors correspond to the treatment listed on the status justification form at initial listing. The dashed line represents October 2018, when the policy was implemented. ECMO = extracorporeal membrane oxygenation; IABP = intra-aortic balloon pump; LVAD = left ventricular assist device; MCS = mechanical circulatory support.
Determining the effects of the new 2018 heart allocation policy on transplant center practices and recipient outcomes
We evaluated the changes in transplant outcomes and practices associated with the 2018 policy shift in several widely-sited papers (e.g., Lazenby et al., 2022; Parker et al., 2020a; Parker et al., 2020b; Ran et al., 2021).
- Practice shifts predicted by our previous work occurred – almost all transplant centers chose aggressive treatment options to increase waitlist priority ranking (Parker et al., 2020a; Ran et al., 2021).
- Because the new policy was intended to prioritize sicker candidates, many transplantation experts feared that post-transplant survival would decline. Indeed, pre-post analyses revealed dramatically lower patient survival (Ran et al., 2021).
Initial studies of post-policy post-transplant survival were limited by heavy censoring, potentially biasing results (Parker et al., 2020b)
Follow-up analyses including an unbiased estimate of the one-year survival metric post-policy period revealed no change relative to the pre-policy period (Lazenby et al., 2022).
These results shaped the narrative in the transplant community;
- An American Journal of Transplantation editorial discussed the importance of our post-transplant survival findings.
- National policy committees repeatedly cited our work in their evaluation of the new allocation system.