Abstract Body (Do not enter title and authors here): Introduction: Clinical trial data and professional guidelines support rhythm control strategies over rate control in patients with comorbid atrial fibrillation (AF) and heart failure (HF). Studies have also shown that males and females experience differences in symptom burden, comorbidities, management strategies, and outcomes. Catheter ablation utilization between sex has not been well described.

Research Questions: We sought to analyze rates of catheter ablation for comorbid AF and HF by patient-reported sex.

Methods: Using the Epic Cosmos database, which provides nationally-representative data by combining electronic health record data from over 1,500 electronic health record systems, we examined trends in catheter ablation rates over time, stratified by sex. Patients were identified if they had at least two encounters between 2015 and 2024 with ICD-10 codes for each of AF and HF. The primary outcome was catheter ablation for AF. Patients were followed until the outcome of interest or 12/31/2024, whichever was earlier.

Results: A total of 2,646,219 patient records with comorbid AF and HF were identified, of which 44.3% were women. There were 137,260 catheter ablations (5.2%). Overall, 5.9% of men and 4.2% of women underwent catheter ablation. Women were 29% less likely to receive catheter ablation (RR = 0.713; 95% CI = 0.705 - 0.721). The catheter ablation rate per 100 new AF diagnoses per year increased by 1.3% among men and 0.9% among women from 2015 to 2024 (p = 0.045) (Figure 1). Under the age of 65, men are significantly more likely to undergo ablation than are women of similar age (p < 0.05) (Figure 2). Above the age of 65, the overall ablation rate decreases, and there is no apparent difference by sex (Figure 2).

Conclusion: Men undergo catheter ablation more frequently than women. Moreover, the difference in ablation rates persists over time despite increasing use of AF ablation overall. Ablation rates are attenuated > 65 years of age, partially masking marked sex-based differences in ablation rates among younger patients, especially those <55 years.