Recurrence Rates and Outcomes After First Detected Atrial Fibrillation Episode in a Contemporary Hypertrophic Cardiomyopathy Center

Background: Atrial fibrillation (AF) is the most common sustained arrhythmia in hypertrophic cardiomyopathy (HCM), occurring in 20–25% of patients and associated with increased morbidity, stroke risk, and symptom burden. Despite this substantial clinical impact, the understanding of the short-term natural history of AF, including recurrence and the effectiveness of treatment strategies in HCM, remains poorly characterized. Methods: We assessed 2016 patients referred to Lahey Hospital and Medical Center for the diagnosis and subspecialty management of HCM, of whom 341 (17%) had a remote history of AF (≥5 years), and 149 (7%) had AF episodes initially detected between January 2020 and June 2025. These 149 patients were included in this retrospective analysis to allow comprehensive short-term assessment of AF recurrence, treatment interventions, and clinical outcomes from first detected AF utilizing contemporary treatments. Results: AF was first detected at a median age of 63 years (IQR 54–70); 63% were male. Most AF episodes (87%) were symptomatic at presentation. Among 146 patients who converted to sinus rhythm, AF recurred in 80 (54%) at a median of 171 days (IQR 53–278; 29% at 6 months, 43% at 12 months). In patients not undergoing rhythm control after first detected AF episode, 60% had spontaneous recurrence (29% at 6 months, 48% at 1 year), while recurrence rates after antiarrhythmic drug (AAD) initiation were 44% (28% at 6 months, 37.5% at 1 year), and after catheter ablation were 27% (9.8% at 6 months, 18% at 1 year). At last follow-up, 1.9 years (IQR 1.2–2.6 years) from first detected AF episode, 133 of 149 patients (89%) were in sinus rhythm. Seven patients (4.7%) died at a median of 1.16 years (IQR 0.74–1.62) after their first detected AF; estimated survival was 98.6% at 1 year and 96.0% at 3 years. Conclusions: AF recurrence occurs at high rates after the initial detected AF episode in HCM regardless of rhythm-control strategy or AAD use. Catheter ablation was associated with lower recurrence rates. These findings characterize the relapsing natural history of HCM-associated AF and underscore the need for further studies to optimize rhythm-control strategies in this population.