Objectives The purpose of this study was to characterize the pattern of atrial remodeling seen with human aging. Background Atrial fibrillation (AF) occurs in 3%to 4%of the population over 65 years of age. It is associated with thromboe mbolic complications, worsening heart failure, and increased mortality, yet the electrical and structural remodeling that occurs with human aging remains unknow n. Methods Thirteen patients (66.4 ±1.7 years) ≥60 years (group A), 13 patient s (50 ±2.1 years) age 31 to 59 years(group B), and 15 patients(24.7 ±1.0 years ) ≤30 years(group C) underwent conventional electrophysiologic studies and elec troanatomic mapping. We measured atrial refractoriness(ERP) at the distal corona ry sinus(CS); low and high lateral right atrium (LRA) and the high septal right atrium at 600, 500, and 400 ms; maximum corrected sinus node recovery time (CSNR T); P-wave duration(PWD); conduction time(CT) along the CS and LRA; and discret e double potentials(DP) along the crista. Results Aging was associated with an i ncrease in atrial ERP, prolonged CT along the CS, increased PWD and CSNRT. There was no significant change in dispersion of refractoriness or rate adaptation. E lectroanatomic mapping revealed diffuse areas of low voltage with regional condu ction slowing. Both techniques demonstrated a greater number of DPs and fraction ated signals along the crista terminalis with aging. Conclusions Aging is associ ated with regional conduction slowing, anatomically determined conduction delay at the crista, and structural changes that include areas of low voltage. In addi tion, impairment of sinus node function and an increase in atrial ERP occurred w ith aging. This electrical and structural remodeling may explain the increased p ropensity to AF with aging. Objectives The purpose of this study was to characterize the pattern of atrial remodeling seen with human aging. Background Atrial fibrillation (AF) occurs in 3% to 4% of the population over 65 years of age. It is associated with thromboe mbolic complications, worsening heart failure, and increased mortality, yet the electrical and structural remodeling that occurs with human aging remains unknow n. Methods Thirteen patients (66.4 ± 1.7 years) ≥60 years (group A), 13 patient s (50 ± 2.1 years) age 31 to 59 years (group B), and 15 patients (24.7 ± 1.0 years) ≤30 years (group C) underwent conventional electrophysiologic studies and elec troanatomic mapping. We measured atrial refractoriness (ERP) at the distal corona ry sinus high and high lateral right atrium (LRA) and the high septal right atrium at 600, 500 and 400 ms; maximum corrected sinus node recovery time (CSNR T); P-wave duration (PWD); conduction time (CT) along the CS and LRA; and discret e double potentials (DP) along the c Results Aging was associated with an icrecrease in atrial ERP, prolonged CT along the CS, increased PWD and CSNRT. There was no significant change in dispersion of refractoriness or rate adaptation. E lectroanatomic mapping revealed diffuse areas of low voltage with regional condu Both techniques demonstrated a greater number of DPs and fraction ated signals along the crista terminalis with aging. Conclusions Aging is associ ated with regional conduction slowing, anatomically determined conduction delay at the crista, and structural changes that include areas of low voltage. In addi tion, impairment of sinus node function and an increase in atrial ERP occurred w ith aging. This electrical and structural remodeling may explain the increased p rope intensity to AF with aging.