Predicted Heart Mass and Severe Primary Graft Dysfunction in Donation After Circulatory Death Heart Transplant.

BACKGROUND: Donation after circulatory death (DCD) has expanded the US heart donor pool yet carries a higher risk of severe primary graft dysfunction (PGD) for recipients compared to donation after brain death (DBD). This study addresses an important knowledge gap of exploring the role of heart size mismatch in contributing to the risk of severe PGD in DCD-HT. METHODS: All heart-only, adult transplants from the united network for organ sharing (UNOS) database were collected from 09/2023-06/2025. Univariable (UV) and multivariable (MV) analyses were used to identify associations between various size matching variables and severe PGD in both DCD-HT and DBD-HT. RESULTS: In the DCD-HT MV analysis, no categorical classifications of size mismatch had significant associations with severe PGD. However, various recipient size metrics, including predicted heart mass (PHM) (OR = 1.01 per gram [1.00-1.01], p = 0.002) were independently associated with severe PGD in DCD-HT. When analyzed in the dataset containing both DCD and DBD cases, PHM's association with severe PGD was found to interact with DCD status (β = 0.009, SE = 0.0032, p = 0.004). CONCLUSIONS: Conventional categorical donor-recipient size-mismatch classifications established in DBD-HT were not associated with severe PGD in DCD-HT. In contrast, larger recipient size was independently associated with an increased risk of severe PGD in DCD-HT, whereas no such association was observed in DBD-HT. These findings highlight potential differences in the determinant of severe PGD between DCD-HT and DBD-HT and support further investigation into the role of recipient size in donor-recipient matching for DCD-HT.