Left Atrial Remodeling and Functional Maladaptations in Obesity: An Invasive Pressure-Volume Analysis

BACKGROUND: Obesity is a major risk factor for atrial fibrillation and heart failure. We aimed to characterize left atrial (LA) structural and functional changes across body mass index (BMI) strata in patients with atrial fibrillation referred for catheter ablation. METHODS: We studied 1040 consecutive patients (67% male; mean age, 62 years; 71% in sinus rhythm). Participants were stratified by BMI (<25.0, 25–29.9, 30–34.9, and ≥35 kg/m 2 ). Comprehensive echocardiographic assessment of LA structure and function was integrated with invasive LA pressure measurements obtained via transseptal access during the ablation procedure. Associations across BMI strata were evaluated using regression analyses. RESULTS: Patients with higher BMI had larger estimated total blood and plasma volumes along with higher LA volumes and pressures, greater cyclic wall stress, and a rightward shift of the estimated LA pressure-volume relationship. Conversely, estimated operant LA stiffness did not differ across BMI strata. BMI-related differences in LA volume were attenuated by body surface area indexing but preserved with height-based indexing. Conventional volumetric indices of LA phasic function were similar across BMI strata, whereas available LA strain indices (n=107) were lower with greater adiposity, consistent with worse LA phasic function. Compared with patients without heart failure, those with heart failure exhibited more pronounced structural, functional, and hemodynamic atrial remodeling, consistent with a more advanced atrial myopathy phenotype. CONCLUSIONS: In patients undergoing atrial fibrillation ablation, higher BMI is associated with a predominantly load-related pattern of LA remodeling, characterized by larger LA volume and pressures, greater cyclic wall stress, and a rightward shift of the estimated pressure-volume relationship. BMI-associated early atrial remodeling may precede overt atrial dysfunction, potentially contributing to the link between excess adiposity, atrial fibrillation, and heart failure with preserved ejection fraction.