Increasing donor-recipient weight mismatch in infant heart transplantation is associated with shorter waitlist duration and no increased morbidity or mortality.

Objectives: Infants awaiting paediatric heart transplantation (PHT) experience long waitlist duration and high mortality due to donor shortage. Using the United Network for Organ Sharing database, we explored if increasing donor-recipient weight ratio (DRWR) >2.0 (recommended cutoff) was associated with adverse outcomes.

Methods: Between 2007 and 2020, 1392 infants received PHT. We divided cohort into 3 groups: A (DRWR ≤1.0, n = 239, 17%), B (DRWR 1.0-2.0, n = 947, 68%), C (DRWR >2.0, n = 206, 15%). Group characteristics and PHT outcomes were analysed.

Results: DRWR ranged between 0.5 and 4.1. Underlying pathology (congenital versus cardiomyopathy), gender, race, renal function and mechanical circulatory support were comparable between groups. Group C patients were more likely to be ventilated, to receive ABO blood group (ABO)-incompatible heart and to have longer donor ischaemic time. Waitlist duration was significantly shorter for group C (33 vs 50 days, P < 0.1). Early outcomes for groups A, B and C were the following (respectively): operative death (6%, 4%, 3%, P = 0.29), primary graft dysfunction (5%, 3%, 3%, P = 0.30), renal failure (10%, 7%, 7%, P = 0.42) and stroke (3%, 4%, 1%, P = 0.36). The DRWR group was not associated with operative death in either congenital (odds ratio (OR) = 0.819, 95% confidence interval (CI) = 0.523-1.282) or cardiomyopathy (OR = 1.221, 95% CI = 0.780-1.912) patients and only significant factor was pre-PHT extracorporeal membrane oxygenation (OR = 4.400, 95% CI = 2.761-7.010). Additionally, survival at 1 year (87%, 87%, 85%, P = 0.80) and 5 years (76%, 78%, 77%, P = 0.80) was comparable between the DRWR groups.

Conclusions: Infants who received PHT with DRWR >2.0, up to 4.1, experienced shorter waitlist duration with no demonstrable increase in peri-transplant complications, operative or late mortality. Historic practice to avoid DRWR > 2.0 due to complications (e.g. hypertension-related stroke, graft dysfunction, death) is not currently supported in infants and stretching DRWR acceptance criteria would decrease PHT waitlist duration and potentially improve waitlist complications and mortality.