Abstract Body: Background: Non-ischemic cardiomyopathy is a major contributor to heart failure and sudden cardiac death in the United States. Atrial fibrillation (AF), the most common sustained cardiac arrhythmia, frequently coexists with cardiomyopathy, further compounding cardiovascular risk. Despite the clinical burden imposed by these conditions, national trends and disparities in non-ischemic cardiomyopathy-related mortality among patients with comorbid AF remain insufficiently characterized.

Hypothesis: We hypothesized that non-ischemic cardiomyopathy-related mortality among patients with comorbid AF has increased over the past two decades and exhibits significant disparities across sex, race, and geographic location.

Methods: We analyzed national mortality data from the CDC WONDER database for individuals aged >35 years from 1999 to 2020. Non-ischemic cardiomyopathy (ICD-10: I42.x) was designated as the underlying cause of death, with AF (I48) as a contributing cause. Age-adjusted mortality rates (AAMRs) per 1,000,000 were calculated, and Joinpoint regression was employed to assess temporal trends and annual percent change (APC). Demographic and regional variations were also evaluated.

Results: A total of 49,155 deaths were attributed to non-ischemic cardiomyopathy with comorbid AF. AAMRs increased significantly from 11.0 (95% CI, 10.4–11.5) in 1999 to 15.4 (95% CI, 14.9–16.0) in 2020, with an APC of 1.6% (p<0.001). Males had nearly double the AAMR of females (18.0 [95% CI, 17.8–18.2] vs. 9.4 [95% CI, 9.3–9.5]). Racial disparities were evident, with African Americans exhibiting the highest AAMR (14.0 [95% CI, 13.6–14.4]), followed by White individuals (13.1 [95% CI, 13.0–13.2]), American Indians (9.0 [95% CI, 7.8–10.3]), and Asians (7.0 [95% CI, 6.5–7.4]). AAMRs were elevated in medium metropolitan areas (13.9 [95% CI, 13.7–14.2]) compared to rural noncore regions (11.4 [95% CI, 11.0–11.8]). Geographically, the West region had the highest AAMR (14.6 [95% CI, 14.4–14.9]), followed by the Midwest (13.7 [95% CI, 13.5–14.0]), South (12.4 [95% CI, 12.2–12.6]), and Northeast (11.7 [95% CI, 11.5–12.0]).

Conclusions: Non-ischemic cardiomyopathy-related mortality with comorbid AF has risen significantly over the past two decades, disproportionately affecting males, African Americans, and urban populations. These findings underscore the need for targeted prevention and management strategies to mitigate these disparities and reduce mortality risk in high-burden populations.