Out of sequence heart transplants: Why, how many, and to whom

Abstract

Background: Heart transplantation (HT) is governed by the Organ Procurement and Transplantation Network, which commissions 56 organ procurement organizations (OPO) to perform allocation. Each allocation follows a match list of eligible donors ranked by urgency. We sought to describe the prevalence of OOS HT, characterize donor and recipient characteristics, and assess if the centers and recipients of OOS donors differ from non-OOS donors.

Methods: Using the Scientific Registry of Transplant Recipients all adult (≥18 years), single organ HT recipients between 1/18/2018-1/1/2024 were identified. We performed network analysis and compared in sequence vs OOS donors with multivariable logistic regression.

Results: Among 18,394 HT, 880 (4.8%) were involved an OOS allocation for any reason (52% were OPO initiated). Four transplant centers received one-quarter (4.3%-8.5% each) of hearts allocated OOS. Six OPOs accounted for 27% of OOS allocations (4.0%-6.6% each). Graft survival was similar at 1-year between groups (90.6% vs 90.9%, p=0.79). Recipient characteristics most associated with OOS heart allocation included blood type O, UNOS Status 4 or 6, and the absence of surgical mechanical circulatory support (MCS). The most common reason for OOS allocation was expedited heart placement and the frequency was stable over time.

Conclusions: OOS heart allocation occurs in 4.8% HT. Nearly all centers and OPOs participated in OOS allocation, but certain were more prevalent. Recipients of OOS hearts more commonly had a lower priority status (Status 4 or 6), blood type O, and did not have surgical MCS. Further study is needed to ensure a balance between utility and equity.

Keywords: Heart Transplant; Organ allocation; Out of sequence; Outcomes; SRTR.