Impact of Size Matching on Survival Post Heart Transplant in Infants: Estimated Total Cardiac Volume Ratio is Better Than Donor-Recipient Weight Ratio

Abstract

<h3>Purpose</h3> Total Cardiac Volume (TCV) is a novel method of donor‒recipient size matching in pediatric heart transplantation (HT). However, usage of donor-recipient TCV ratio, instead of the donor-recipient weight ratio (DRWR) is still controversial. This study sought to determine whether estimated (e)TCV ratio is associated with infant post-transplant survival. <h3>Methods</h3> The United Network for Organ Sharing (UNOS) was used to search for infants (age: <1 year) who were listed for and received HT in 1987-2020. Donor and recipient eTCV were calculated from weight using previously published data. This equation is derived and validated from measured TCV in 140 donor-like CT scans. Cubic spline was used to determine optimal eTCV ratio range that significantly predicts survival. Patient cohort was divided according to the significant range and survival was compared. <h3>Results</h3> A total of 2864 infants were identified. The optimal eTCV ratio predictive of infant survival was 1.05-1.85. 70% (n=2166) patients had an optimal TCV ratio, while 16.7% (n=517) were in the lower (LR) and 5.9% (n=181) in the higher (HR) group. Kaplan-Meier analysis showed better survival for patients within the optimal vs LR (p<0.001), and similar survival compared to HR (p=0.08; figure). A 2-year conditional survival showed that LR had similar survival to the optimal group (p=0.76), and HR had worse survival than the other groups (optimal, p=0.002; LR p=0.02) (figure). Infants with optimal eTCV ratio (n=2166) had DRWR ranging from 1.09-5. Of these 33.6% had DRWR 2-3, and 5.8% DRWR>3. <h3>Conclusion</h3> Currently, an upper DRWR limit has not been established in infants. Therefore, the eTCV range determined is important since it identifies a potential upper limit that significantly predicts survival. This also implies that this finding can increase donor utilization since the eTCV range includes DRWR ranges that are frequently not used.