Abstract Body (Do not enter title and authors here): Background: The purpose of this study was to describe outcomes after heart transplantation in adults with congenital heart disease (CHD) based on the experience from a high volume transplant center.

Method: Retrospective cohort study of adults with CHD who underwent heart transplantation at Mayo Clinic Rochester, MN (2003-2024).

Results: Of 89 patients (age 40 [9;66], 52% males) who underwent heart transplantation, 67 (75%) had biventricular physiology while 22 (25%) had Fontan physiology. Fifty (56%) and 39 (44%) receives single organ versus multi-organ transplantation, respectively. The proportion of patients with Fontan palliation undergoing heart transplantation was higher in the late (after 12/31/2023) era 31% [21 /67] versus 5% [1/22], p=0.005.The 30-day, 1-year, and 5-year survival rates were 97%, 91%, and 87%, respectively, and these rates were higher than the estimates from national registries. Patients with Fontan physiology had lower post-transplant survival compared to biventricular physiology, but Fontan physiology was not an independent predictor of mortality. The predictors of post-transplant mortality were longer cardiopulmonary bypass time, mechanical ventilation duration and postoperative mechanical circulatory support.

Conclusions: We observed a higher post-transplant survival compared to historical estimates. Post-transplant mortality was related to operative and postoperative factors, and not to CHD physiology. There was a high proportion of patients requiring multi-organ transplantation, and a rising proportion of patients with Fontan physiology who underwent transplant in the later part of the study. These findings highlight important demographic changes, importance of institutional expertise, and the need for improvements in risk stratification and referral patterns to align with these changes.