Sex-stratified trends in hypoplastic left heart syndrome-related mortality among children and young adults in the United States, 1999-2024: a pre- and post-COVID-19 analysis.

Background: Hypoplastic left heart syndrome (HLHS) is a congenital heart disease that accounts for approximately 3% of congenital heart defects, making it a leading cause of mortality in this population. Timely staged palliation, such as Norwood, Glenn, and Fontan, are required to reduce the incidence of adverse outcomes. Data over the long term suggest that only about 31% of patients with HLHS are alive at age 35 years after Fontan completion. However, national mortality trend data stratified by sex, extending through 2024 and spanning the COVID-19 era, have not been characterised. Methods: Data for this study were obtained from the CDC WONDER (Centres for Disease Control and Prevention Wide-ranging Online Data for Epidemiologic Research) Multiple Cause of Death database using ICD-10 code Q23.4 from 1999 through 2024 in individuals aged 0-24 years. Joinpoint regression was used to analyse trends. Analyses were conducted using a Poisson variation model with Monte Carlo permutation testing. Statistical significance was defined as Results: A total of 10,138 deaths were identified in the United States during the study period. Among these, 4,285 were females, and 5,853 were males. Joinpoint regression identified a declining trend from 1999 to 2021 (APC: -2.22%; 95% CI: -3.08 to -1.89; Conclusion: HLHS mortality has declined following surgical advances and perioperative care management. Persistent higher mortality rates were noted among males than females throughout both pre- and post-COVID eras. The rise in post-pandemic mortality is a new and concerning trend that warrants close national monitoring. These trends emphasise the need for uninterrupted staged palliation and continued population-level surveillance of HLHS outcomes.