UC Irvine

BACKGROUND: Infants account for a significant proportion of pediatric heart transplantation but also suffer from a high waitlist mortality. Donor oversizing by weight-based criteria is common practice in transplantation and is prevalent in this group. We sought to analyze the impact of oversizing on outcomes in infants. METHODS: Infant heart transplantations reported to the United Network for Organ Sharing from January 1994 to September 2019 were retrospectively analyzed. 2384 heart transplantation recipients were divided into quintiles (Q1-Q5) on the basis of donor-to-recipient weight ratio (DRWR). Multivariate Cox regression was used to estimate the effect of DRWR. The primary end point was graft survival at 1 year. RESULTS: The median DRWR for each quintile was 0.90 (0.37-1.04), 1.17 (1.04-1.29), 1.43 (1.29-1.57), 1.74 (1.58-1.97), and 2.28 (1.97-5.00). Pairwise comparisons showed improved survival for Q3 and Q4 over each of the bottom 2 quintiles and the top quintile. Regression analyses found that Q3 and Q4 were protective against graft failure compared with the bottom 2 quintiles. There was no difference in hazard among the top 3 quintiles. Significant covariates included primary diagnosis, ischemia time, serum bilirubin level, transplantation year, mechanical ventilation at transplantation, and extracorporeal membrane oxygenation at transplantation. Sex, female-to-male transplantation, and mechanical circulatory support at transplantation were not significant in univariate analyses. CONCLUSIONS: Modest oversizing by DRWR (1.29-1.97) is associated with increased survival and lower risk in infant heart transplantation. Additional investigation is needed to establish best practices for size matching in this population.