Effect of ischemic time on pediatric heart transplantation outcomes: is it the same for all allografts?

Abstract

Studies have shown that the optimal ischemia time (IT) threshold in pediatric heart transplantation (PHT) is up to 4h, independent of other donor organ factors. The purpose of this study was to examine the relationship between IT and donor left ventricular ejection fraction (LVEF) and study their impact on PHT outcomes. This is a retrospective cohort study of PHT (<18years) identified in UNOS between January 2000 and March 2020. Post-transplantation survival analysis of patients receiving donor hearts with IT<4, 4-6, and >6h was performed using Kaplan-Meier curves. Cohort was divided according to donor LVEF median value, and survival was analyzed. Cox regression was performed. Median LVEF was 65% in the study cohort (6669 PHT). Overall, IT>6h was associated with worse survival compared to <4h regardless of donor LVEF. For allografts with LVEF<65%, IT=4-6h was associated with worse survival compared with IT<4h (p=.006) but had similar survival compared with IT>6h (p=.315). For allografts with LVEF≥65%, IT=4-6h had similar survival compared with <4h (p=.175) but improved survival compared with >6h (p=.003). After adjusting for donor and recipient variables, Cox regression showed that IT=4-6h was not associated with increased mortality for LVEF≥65%. The IT threshold of 4h does not apply to all allografts. Recipients of hearts with LVEF≥65% can tolerate an IT up to 6h without any detriment to survival. Routine acceptance of these donor hearts could mitigate longer waiting times and poor donor availability for many candidates.