Background: Aging induces structural remodeling, altering atrial electrogram morphology. Over time, structural and consequently electrical remodeling creates a substrate for atrial fibrillation. In structural heart disease, age-induced remodeling comes on top of a pre-existing degree of structural remodeling due to pressure or volume overload. Objective: Investigate the severity of age-related electrical remodeling in patients undergoing surgery for structural heart disease by utilizing a high resolution epicardial mapping approach. Methods: Five seconds of sinus rhythm were recorded intraoperatively at the right atrium (RA), Bachmann's bundle (BB), the left atrium, and the pulmonary vein area. Potential voltage, low-voltage area (LVA) and conduction velocity (CV) were assessed in all regions. Results: 104 patients were included (62,5 % male, age: 26–84 years) and categorized in three age groups: young-age (age <60 years, n = 40), middle-age (age 60–71 years, n = 33), or old-age (age ≥72 years, n = 31) group. Compared to the young-age group, the old-age group had 1) lower median potential voltages at RA (4.65 [3.53–5.62]mV versus 5.94 [4.86–6.79]mV, p = 0.001) and 2) lower CV at RA (87.86 [82.53–96.67]cm/s versus 94.81 [90.14–98.59]cm/s, p = 0.016) and BB (83.38 [67.72–94.96]cm/s versus 98.84 [86.58–102.90]cm/s, p = 0.005). Conclusions: Age-related electrophysiological changes in patients with structural heart disease include reduction in atrial potential voltages and slowing of CV. These changes were less pronounced in the middle-age group. This indicates that electrical remodeling is a combination of both the underlying heart disease and the aging process. However, the less pronounced changes in the middle-age group may reflect a more gradual progression of age-related remodeling.