Out-of-Sequence Donor Heart Allocation: A United Network for Organ Sharing Registry Analysis.

Background: Out-of-sequence (OOS) allocation is a mechanism by which donor organs are offered outside the standard match run, typically to expedite the placement of hard-to-match or time-sensitive allografts. Rising OOS rates are described in abdominal organ transplantation, but limited data exist regarding OOS practices in heart transplantation.

Methods: The United Network for Organ Sharing (UNOS) was used to identify all adult heart transplant recipients and corresponding donors between January 2015 and March 2024. The Potential Transplant Recipient file was then used to classify each donation as either in-sequence or out-of-sequence. We assessed temporal trends and practice patterns in relation to OOS allocation. Additionally, we evaluated donor and recipient characteristics and post-transplant survival outcomes.

Results: Within the study period, there were 25,608 heart transplantations, of which 509 (2%) were from OOS donors. OOS allocation increased 2-fold over the study period (1.4%-3.1%). Use varied across Organ Procurement Organizations (OPOs) (0-5.4%) and transplant centers (0-16.7%), with a small subset of OPOs accounting for the majority of OOS allocations. Recipients of OOS-allocated allografts were more likely to be nonhospitalized older females with type O blood group. There was no significant difference in overall survival rates between OOS and in-sequence recipients at 1 year (93.1% vs 91.6%, respectively).

Conclusions: OOS heart allocation, while rare, is increasing, and varies by geography and OPO. The OOS mechanism may provide an opportunity to improve organ recovery and support transplant access for harder-to-match candidates. However, standardization of OOS practices is needed to ensure equity in transplant access.