Survival trajectories in post-transplant patients receiving "acceptably" undersized donor hearts: a long-term analysis
S Kumar, M Berman, H Smail, S Bhagra, S Moule, S PettitAbstract
Background
Appropriate organ size matching between donor and recipient is associated with improved survival after heart transplantation. Predicted heart mass (PHM) ratio has been used for donor-recipient size matching in recent years. Recent International Society of Heart and Lung Transplantation guidelines state that a donor-recipient PHM ratio under 0.86 is a predictor of increased one-year mortality. However, the longer-term prognostic impact of more "acceptably" undersized hearts (PHM between 0.86 and 1.00) compared to oversized hearts is less well studied.
Purpose
This study compared long-term survival trajectories of patients receiving "acceptably" undersized (PHM ratio between 0.86 and 1.00), oversized (PHM ratio over 1.00), and "severely" undersized (PHM ratio less than 0.86) donor hearts.
Methods
We examined all adult patients undergoing heart transplantation at a single UK centre between January 2012 and October 2025. PHM was calculated for donors and recipients using the multi-dimensional Reed formula (incorporating height, weight, age, and sex). Patients were stratified into three groups: "severely" undersized (PHMR <0.86), "acceptably" undersized (0.86≤ PHMR ≤ 1.00), and oversized (PHMR >1.00). The primary endpoints were death or acute re-transplantation. Survival was analysed using the Kaplan-Meier method and Cox proportional hazards models adjusted for donor and recipient age and sex.
Results
Of 543 patients undergoing heart transplantation during the study period, 508 were included in the final analysis with a median follow-up of 66.0 months (IQR 27.7–106.7 months). 43 patients (8.5%) received a "severely" undersized heart, 161 (31.7%) patients received an "acceptably" undersized heart, and 304 (59.9%) received an oversized heart. "Acceptably" undersized hearts demonstrated comparable long-term survival with oversized hearts (unadjusted HR 0.83, 95% CI 0.56-1.22, p = 0.334; adjusted HR 0.72, 95% CI 0.47-1.10, p = 0.126) and significantly improved long-term survival compared to "severely" undersized hearts (unadjusted HR 1.71, 95% CI 1.01-2.92, p = 0.048; adjusted HR 1.79, 95% CI 1.02-3.13, p = 0.043). Primary graft dysfunction accounted for 30.0% of deaths in the "severely" undersized group compared to 4.9% of deaths in the "acceptably" undersized group (p = 0.016).
Conclusions
Our study suggests patients receiving "acceptably" undersized hearts have comparable long-term survival to those receiving oversized hearts and better long-term survival than those receiving "severely" undersized hearts. Higher rates of primary graft dysfunction in recipients of "severely’ undersized hearts may explain this difference. Future studies will explore whether the association between donor-recipient size-matching and survival is influenced by any other donor, recipient, or operative characteristics.Figure 1For image description, please refer to the figure legend and surrounding text.