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Updated: Sep 14, 2025
A Modified Method for Heterotopic Mouse Heart Transplantion
Published on: June 23, 2014
Out of sequence heart transplants: Why, how many, and to whom
Kevin J Clerkin1, Gabriel Sayer1, Ersilia M DeFilippis1
1Seymour, Paul, and Gloria Milstein Division of Cardiology, Department of Medicine, Columbia University Irving Medical Center/NewYork-Presbyterian Hospital, New York, NY.
Insights
Out-of-system (OOS) heart transplants occur in 4.8% of cases, often for expedited placement. Recipients typically have lower priority status and blood type O, with similar graft survival to standard allocations.
Area of Science:
- Transplantation Medicine
- Organ Allocation Systems
- Cardiovascular Surgery
Background:
- Heart transplantation (HT) allocation is managed by the Organ Procurement and Transplantation Network (OPTN) through 56 organ procurement organizations (OPOs).
- Urgency-based match lists prioritize eligible donors for recipients.
- Understanding out-of-system (OOS) heart transplant prevalence and characteristics is crucial for optimizing allocation.
Purpose of the Study:
- To describe the prevalence of OOS heart transplantation (HT).
- To characterize donor and recipient demographics in OOS HT.
- To assess differences between OOS and in-system donors, centers, and recipients.
Main Methods:
- Analysis of adult, single-organ HT recipients from the Scientific Registry of Transplant Recipients (2018-2024).
- Network analysis and multivariable logistic regression comparing in-sequence versus OOS donors.
- Comparison of donor and recipient characteristics.
Main Results:
- 4.8% of 18,394 HTs involved OOS allocation (52% OPO-initiated).
- Specific transplant centers and OPOs accounted for a disproportionate share of OOS allocations.
- Recipients of OOS hearts often had blood type O, UNOS Status 4 or 6, and lacked surgical mechanical circulatory support (MCS).
- One-year graft survival was similar between OOS and in-system groups (90.6% vs 90.9%).
Conclusions:
- OOS heart allocation is a notable, though not predominant, component of HT, occurring in 4.8% of cases.
- While most centers and OPOs participate, OOS allocation is more concentrated in certain entities.
- OOS heart recipients frequently present with specific characteristics, including lower UNOS status and blood type O.
- Further research is warranted to balance organ allocation utility and equity.
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.
