Weight Matching in Infant Heart Transplantation: Analysis of the United Network for Organ Sharing Database

Abstract

<h3>Purpose</h3> Infants (0-12 months) account for a significant proportion of pediatric heart transplants, 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. <h3>Methods</h3> Infant heart transplantations reported to UNOS from 01/1994 to 09/2019 were retrospectively analyzed. 2159 heart transplantation recipients were divided into quintiles (Q1-Q5) based on donor-to-recipient weight ratios (DRWR). Primary endpoint was graft survival at one year. <h3>Results</h3> The median DRWR for each quintile was 0.90 (0.36 to 1.04), 1.17 (1.04 to 1.29), 1.43 (1.29 to 1.57), 1.74 (1.58 to 1.97), and 2.28 (1.97 to 5.00). Pairwise comparisons showed improved survival for the middle quintile over the bottom two quintiles (Q1: p=0.006; Q2: p=0.006) and the top quintile (Q5: p=0.04). Q4 demonstrated improved survival over Q2 (p=0.04) (Figure 1). In multivariate Cox regression, the top three quintiles (Q3, Q4, Q5) were protective against graft failure when compared to Q2 (HR: 0.48, p<0.0001; HR: 0.61, p=0.007; HR: 0.61, p=0.01) and Q1 (HR: 0.49, p=0.0002; HR: 0.63, p=0.01; HR=0.63, p=0.02). There was no difference in hazard amongst the top three quintiles. Significant covariates included ischemic time (HR: 1.11, p=0.01), serum bilirubin (HR: 1.05, p<0.0001), number of previous transplantations (HR: 2.72, p<0.0001), transplant year (HR: 0.96, p<0.0001), diagnosis of dilated cardiomyopathy (vs congenital heart disease; HR: 0.43, p<0.0001), and ECMO at transplantation (HR: 3.68, p<0.0001). Gender, female-to-male transplantation, and mechanical circulatory support at transplantation were not significant in univariate analyses. <h3>Conclusion</h3> Modest oversizing by DRWR 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.