P2.029: Temporal Trends in Mortality Attributed to Hypoplastic Left Heart Syndrome in Fontan-Era in the United States, 1999–2020

Background: Hypoplastic Left Heart Syndrome (HLHS) is a severe congenital heart defect characterized by single ventricle physiology with right ventricular dominance, treated through staged Fontan palliation. While Fontan techniques have advanced, their long-term impact on survival at the national level remains unclear. This study aimed to assess temporal trends in HLHS-related mortality in the United States using national population-based data reflecting two decades of significant advancements in the Fontan palliation technique.

Methods: Data was extracted from the Centers for Disease Control and Prevention Wide-ranging Online Data for Epidemiologic Research (CDC WONDER) underlying cause of death database from 1999 to 2020. CDC defines underlying cause of death to be a disease or injury that initiated the sequence of events directly leading to death. Deaths attributed to Hypoplastic Left Heart Syndrome (HLHS) were identified using the ICD-10 code Q23.4. HLHS was selected as the representative lesion for single ventricle physiology given its consistent management using Fontan Palliation. Other single ventricle diagnoses were excluded from this study due to the variable nature of surgical approaches performed. Furthermore, the relatively low prevalence and mortality counts associated with other single ventricle lesions limited the feasibility of robust temporal and subgroup analysis. Annual age-adjusted mortality rates (AAMR) per 100,000 population were extracted and stratified by sex and race. Temporal trends were assessed using linear regression and visualized using line graphs. Due to limited case numbers and inconsistent reporting, Hispanic origin-specific data were excluded from trend analyses.

Results: 6,909 deaths were attributed to HLHS between 1999 and 2020. The AAMR declined during this period, with a slope of –0.0031 and an R² of 0.6657 (Figure 1). This decline reflects major advancements in staged Fontan palliation along with improved perioperative care and follow-up strategies. Male rates peaked at ~0.36 per 100,000 in 2000 and declined to ~0.20 by 2020. Female rates fell from ~0.16 to ~0.10 from 2000 to 2020. The trend reflects improved outcomes despite persistent sex disparities. AAMR was the highest among White infants, followed by Black or African American infants. Rates in White infants declined from ~0.36 to ~0.20 per 100,000, while rates in Black infants dropped from ~0.20 to ~0.10. Mortality rates in Asian or Pacific Islander infants remained consistently low throughout the period. The data highlights persistent racial disparities despite overall improvements (Figure 2).

Conclusion: In this new Fontan era, AAMR due to HLHS has notably decreased. However, persistent disparities by sex and race remain. These findings underscore the importance of equitable access to care and continued surveillance of long-term Fontan outcomes at a national level.