AbstractBackgroundIt is unknown which features of unipolar atrial electrogram (U-AEGM) morphology are affected by ageing and whether age-related changes in U-AEGM morphology are equally distributed throughout the right and left atria.Patients and methodsEpicardial high-resolution mapping was performed in patients undergoing coronary artery bypass grafting surgery during sinus rhythm (SR). Mapping areas include the right atrium (RA), left atrium (LA), pulmonary vein area (PVA) and Bachmann’s bundle (BB). Patients were categorized into a young (age < 60) and aged (age ≥ 60) group. U-AEGM were classified as single potentials (SPs, one deflection), short double potentials (SDPs, deflection interval ≤ 15ms), long double potentials (LDPs, deflection interval > 15ms) and fractionated potentials (FPs, ≥3 deflections).ResultsA total of 213 patients (age: 67 (59–73) years; young groupN= 58, aged groupN= 155) were included. Only at BB, the proportion of SPs (p= 0.007) was significantly higher in the young group, while the proportion of SDPs (p= 0.051), LDPs (p= 0.004) and FPs (p= 0.006) was higher in the aged group. After adjusting for potential confounders, older age was associated with a reduction in SPs [regression coefficient (β): −6.33, 95% confident interval (CI): −10.37 to −2.30] at the expense of an increased proportion of SDPs (β: 2.49, 95% CI: 0.09 to 4.89), LDPs (β: 1.94, 95% CI: 0.21 to 3.68) and FPs (β: 1.90, 95% CI: 0.62 to 3.18).ConclusionsAge-related remodeling particularly affects BB as indicated by the decreased amount of non-SP at this location in the elderly.Key MessagesAgeing preferentially affects the morphology of unipolar atrial electrograms recorded at Bachmann’s bundle.At Bachmann’s bundle, the proportion of short double-, long double- and fractionated potentials increase during ageing at the expense of a decrease in the proportion of single potentials, reflecting aggravation of abnormalities in conduction.The increase in abnormal unipolar atrial electrograms at Bachmann’s bundle during ageing supports the concept that Bachmann’s bundle may play an important role in development of age-related arrhythmias such as atrial fibrillation.