Background:The numberof patients awaiting heart transplantation (HTx) substantially exceeds the number of donor hearts transplanted each year, yet nearly 65% of eligible donor hearts are discarded rather than transplanted. Methods: Deceased organ donors listed within the UNOS Deceased Donor Database between 2010 and 2020 were reviewed. Those greater than 10 years old and consented for heart donation were included and randomly separated into training (n = 48 435) and validation (n = 24 217) cohorts. A discard risk index (DSRI) was created using the results of univariable and multivariable analyses. Discard data were assessed at DSRI value deciles, and stratum-specific likelihood ratio (SSLR) analysis and Kaplan-Meier survival function were used for mortality data. Results: Factors associated with higher DSRI values included donor age > 45, LVEF, HBV-core antibodies, hypertension, and diabetes. The DSRI C-statistic was .906 in the training cohort and .904 in the validation cohort. The DSRI did not reliably predict 30day or 1-year mortality after transplantation (C-statistic .539 and .532, respectively). Conclusions:The factors leading to heart allograft discard are not correlated to the same degree with post-transplant outcomes. This suggests that optimizing utilization of certain allografts with slightly higher risk of discard could increase the heart donor pool with limited impact on posttransplant mortality. K E Y W O R D Sdeceased, donors and donation, donation after brain death (DBD), donor evaluation, organ acceptance, risk assessment/risk stratification INTRODUCTIONOrthotopic heart transplantation (HTx) exists as a crucial therapy for patients with end-stage heart disease. While the number of HTxs performed annually has increased over the last 2 decades, the number of patients on the waiting list also continues to grow. 1 Heart transplantation is limited by the availability of deceased donor heart allografts, yet a high proportion of potential donor hearts are discarded rather than transplanted. 2 Finding ways to bridge the gap between the supply and demand for donor hearts is of critical importance,