Practice Changes at U.S. Transplant Centers After the New Adult Heart Allocation Policy

Abstract

Background: In October 2018, the U.S. heart allocation system expanded the number of priority "status" tiers from 3 to 6 and added cardiogenic shock requirements for some heart transplant candidates listed with specific types of treatments.

Objectives: This study sought to determine the impact of the new policy on the treatment practices of transplant centers.

Methods: Initial listing data on all adult heart candidates listed from December 1, 2017 to April 30, 2019 were collected from the Scientific Registry of Transplant Recipients. The status-qualifying treatments (or exception requests) and hemodynamic values at listing of a post-policy cohort (December 2018 to April 2019) were compared with a seasonally matched pre-policy cohort (December 2017 to April 2018). Candidates in the pre-policy cohort were reclassified into the new priority system statuses by using treatment, diagnosis, and hemodynamics.

Results: Comparing the post-policy cohort (N = 1,567) with the pre-policy cohort (N = 1,606), there were significant increases in listings with extracorporeal membrane oxygenation (+1.2%), intra-aortic balloon pumps (+ 4 %), and exceptions (+ 12%). Listings with low-dose inotropes (-18%) and high-dose inotropes (-3%) significantly decreased. The new priority status distribution had more status 2 (+14%) candidates than expected and fewer status 3 (-5%), status 4 (- 4%) and status 6 (-8%) candidates than expected (p values <0.01 for all comparisons).

Conclusions: After implementation of the new heart allocation policy, transplant centers listed more candidates with extracorporeal membrane oxygenation, intra-aortic balloon pumps, and exception requests and fewer candidates with inotrope therapy than expected, thus leading to significantly more high-priority status listings than anticipated. If these early trends persist, the new allocation system may not function as intended.

Keywords: allocation; ethics; heart transplantation.

Figure 1:. Predicted and Observed Status Distribution in the New US Heart Allocation System.

Predicted (top) Status distribution was created by applying the Status 1–6 listing criteria to the seasonally matched pre-policy cohort. Observed (bottom) Status distribution is histogram of actual listing Statuses utilized during the post-policy cohort. See supplement for details regarding classification of the pre-policy cohort into Statuses 1–6. Colors correspond to the treatment listed on the justification form for each status level.

Figure 2:. Trends in Adult Heart Transplant Candidates Subject to Hemodynamic Requirements in the New Heart Allocation System.

Trends in the number of candidates listed with low-dose inotropes, high-dose inotropes (with invasive hemodynamic monitoring), and IABP from December 2017 to April 2019. Listings prior to policy implementation are stratified by whether or not the candidates met the hemodynamic requirement for their respective therapy. ECMO and percutaneous temporary mechanical circulatory support devices were excluded due to low numbers of candidates listed each month (see Table 2).

Figure 3:. Cardiac Index of Adult Heart Transplant Candidates subject to hemodynamic criteria in the new allocation system.

Trends in the mean cardiac index of candidates listed with low-dose inotropes, high-dose inotropes (with invasive hemodynamic monitoring), and IABP from December 2017 to April 2019. Mean cardiac index values recorded on the transplant candidate registration form (pink) are typically entered by a transplant coordinator after listing looking back in the medical record. Mean cardiac index values from the Status justification form are those used to qualify for status in real-time and are subject to the hemodynamic requirements post-policy. Only pairs of measurements where inotropic support at the time of measurement were concordant (i.e. both on or both off) were included. Error bars correspond to 95% confidence intervals of the means. ECMO and percutaneous temporary mechanical circulatory support devices were excluded due to low numbers of candidates listed each month (see Table 2).

Central illustration:. Trends in treatments used to list adult heart transplant candidates during the transition to the new heart allocation policy

Trends in the 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.