Abstract 4364292: The Overlap of Atrial Fibrillation and Sudden Cardiac Death Unmasking the Hidden Role of Hypertrophic Cardiomyopathy in the US Population From 1999 to 2020

Introduction: Hypertrophic cardiomyopathy with atrial fibrillation and sudden cardiac death represents a high-risk triad. Despite advances in care, national trends in HCM-related arrhythmic deaths remain underexplored. Evaluating long-term patterns from 1999 to 2020 may reveal key disparities in diagnosis, management, and outcomes. Hypothesis: We hypothesised that HCM-related arrhythmic mortality involving AFib and SCD would show significant variation by demographic and geographic factors among U.S. adults aged ≥25 years between 1999 and 2020. Methods: We used CDC WONDER Multiple Cause of Death data (1999–2020) to identify decedents aged ≥25 years with HCM (I42.1,I42.2) and coexisting AFib/SCD (I46.0, I46.1, I46.9, I48, R96.0, R96.1). Age-adjusted mortality rates per 100,000 were calculated using the 2000 US Standard Population. Trends were analyzed using Joinpoint regression with APC and AAPC, stratified by sex, age, race/ethnicity, region, and urbanization.Significance was set at p < 0.05 Result: Between 1999 and 2020, 6,963 deaths from hypertrophic cardiomyopathy (HCM) with coexisting atrial fibrillation (AFib) and sudden cardiac death (SCD) were reported in the U.S., with the age-adjusted mortality rate (AAMR) rising slightly from 0.154 to 0.179 per 100,000 (overall AAPC: -0.18%; 95% CI: -1.49 to 1.15). In 1999, AAMRs were equal for males and females (0.157), but by 2020, males had a higher rate (0.167 vs. 0.134). The West had the highest AAMR in both 1999 (0.237) and 2020 (0.225), while the South had the lowest (0.104 and 0.095, respectively). Black individuals had the highest AAMR in 1999 (0.235), declining to 0.214 by 2020; Hispanics had the lowest rate in 2020 (0.066), while Whites recorded the lowest in 1999 (0.154). Urban areas had higher AAMRs in both years (0.159 to 0.188); rural rates increased from 0.099 to 0.146. The highest crude rate was in adults aged ≥85 (1.733 in 1999 to 1.443 in 2020), while the lowest was in those aged 35–44 (0.047 to 0.059). The sharpest decline occurred in the 75–84 group (AAPC: -1.71%; 95% CI: -2.90 to -0.50). No significant trends emerged by gender, region, or race/ethnicity. Conclusion: Despite stable overall mortality, significant disparities persisted by sex, race, region, and age. Higher burdens were observed among older adults, urban populations, and Black individuals, highlighting the urgent need for equitable prevention in HCM-related arrhythmic deaths.