Abstract Body (Do not enter title and authors here): Background
Advances in surgical and medical care of children born with congenital heart disease (CHD) has improved survival into adulthood. However, cardiac and non-cardiac morbidity and mortality remain common in adults with CHD (ACHD). We present the causes and predictors of mortality in a large cohort of ACHD patients from the USA.

Methods/Approach:
We conducted a retrospective review of ACHD patients followed at Mayo Clinic between 1992 - 2024. Mortality was ascertained using the Accruint national data base. Clinical characteristics and primary cause of death were identified from the electronic record. Kaplan-Meier (KM) survival analysis was performed to compare overall survival stratified by CHD severity. Cox proportional hazards regression was used to identify independent predictors of mortality.

Results/Data:
Amongst 9160 ACHD patients (mean age 38±16y at first visit, 51% males, 23% simple, 59% moderate and 18% severe CHD), mortality occurred in 1430(16%) patients during a mean follow-up of 11±7y. The mean age at death was 68±17 y, 58±17y, and 45±15y in mild, moderate and severe ACHD. KM analysis of survival and cause of death stratified by CHD severity are presented in Figures 2 and 3 respectively. Cause of death could not be ascertained in 33%%. Amongst those with a known cause of death, the proportion of non-cardiac death increased with decreasing severity of CHD. HF death and sudden cardiac death occurred in 11% and 19%. Infection, malignancy and chronic respiratory failure were important non-cardiac causes of death. Significant risk factors for mortality included CHD severity, ventricular arrhythmia, heart failure, declining functional capacity, diabetes and chronic kidney disease as presented in the Fig 1.

Conclusion(s):
Mortality in ACHD patients is associated with CHD severity, heart failure, ventricular arrhythmia and cardiovascular comorbidities. Early recognition and management of these risk factors may improve long-term survival. As patients with ACHD age, management of cardiovascular and noncardiac risk factors will require development of systems of care specific to this vulnerable population.