Abstract 15629: Optimal Metrics for Assessing Donor-recipient Size Mismatch in Pediatric Heart Transplantation: A PHTS Multi-institutional Analysis

Introduction: Traditional weight & height ratios as measures of donor-recipient (D-R) matching have been challenged in adult heart transplantation (HT). The optimal metrics for D-R matching in pediatric HT remain unclear, and were evaluated in the present study. Methods: All primary pediatric HT recipients in the Pediatric Heart Transplant Society database transplanted from 1993-2019 were included. Multiple metrics of size matching - height, weight, body mass index (BMI), body surface area (BSA), predicted heart mass (PHM) and total cardiac volume (TCV) were assessed to identify the metrics that would best predict 1-year post-transplant (PTx) graft loss (death/re-transplant). Kaplan-Meier analyses (risk unadjusted) and multivariate Cox proportional hazard models (risk adjusted) were used to assess the effect of differences of various size matching metrics on survival. Results: Among 6903 D-R pairs, multivariable hazard modeling identified the following risk factors for PTx mortality: female sex, black race, bilirubin, ECMO, VAD, mechanical ventilation, ICU admission at the time of transplant, presence of congenital heart disease, early era of transplant, donor ischemic time and cardiopulmonary bypass time. After adjusting for all covariates, increasing size mismatch by height, BSA, or PHM was associated with increased 1-year PTx graft loss, with a disproportionately higher hazard for undersized donors than oversized donors (Figure). Weight, BMI and TCV were not predictive of 1-year PTx graft loss on multivariate analysis. Conclusions: In pediatric HT recipients, increasing size mismatch by height, BSA and PHM is associated with increased 1-year PTx graft loss. Undersizing donors appears to carry a higher risk than oversizing.