Abstract 4371994: Impact of Atrial Fibrillation on 1-Year Clinical Outcomes in Hypertrophic Cardiomyopathy: A Multicenter Observational Analysis

Background: Atrial fibrillation (AF) is a common comorbidity in hypertrophic cardiomyopathy (HCM), yet its incremental impact on clinical outcomes remains incompletely defined. We leveraged a large, federated electronic health record network to quantify 1-year risks associated with AF in HCM. Methods: Using TriNetX’s US Collaborative Network, we identified adults (≥18 years) with HCM. Two cohorts were formed: HCM + AF (n = 54 852) and HCM without AF (n = 130,250). After 1:1 propensity score matching for demographics and comorbidities (yielding 51,750 patients per cohort), we assessed 1-year outcomes commencing 1 day post–index date. Outcomes included all-cause mortality, ischemic stroke, heart failure (HF) hospitalization, ventricular arrhythmias, sudden cardiac arrest (SCA), pacemaker/implantable cardioverter-defibrillator (ICD) implantation, and left atrial appendage occlusion (LAAO). Hazard ratios (HRs) with 95% confidence intervals (CIs) were generated using Kaplan-Meier and Cox analyses. Results: In matched cohorts (mean age 72 years, 45% female), HCM + AF was associated with significantly higher 1-year mortality (9.8% vs. 5.1%; HR 1.92 [1.84–2.02]; p < 0.0001). AF conferred a 1.61-fold increase in stroke risk (2.9% vs. 1.8%; HR 1.61 [1.48–1.76]; p < 0.0001) and a 2.21-fold higher risk of HF hospitalization (14.4% vs. 6.7%; HR 2.21 [2.10–2.32]; p < 0.0001). Ventricular arrhythmias were more frequent in HCM + AF (5.7% vs. 2.2%; HR 2.66 [2.48–2.87]; p < 0.0001), as was SCA (1.3% vs. 0.6%; HR 2.38 [2.08–2.74]; p < 0.0001). Device interventions—including pacemaker (3.1% vs. 1.1%; HR 2.70 [2.45–2.97]; p < 0.0001), ICD implantation (1.2% vs. 0.4%; HR 2.95 [2.51–3.45]; p < 0.0001), and LAAO (1.0% vs. 0.05%; HR 19.58 [13.20–29.04]; p < 0.0001)—were significantly more common in the AF cohort. Conclusions: Among HCM patients, AF nearly doubles 1-year mortality risk and substantially increases thromboembolic, heart failure, and arrhythmic events, as well as device/procedural interventions. These findings underscore the necessity for vigilant AF surveillance and tailored management strategies in HCM.