Age-Related Electrophysiological Changes of the Atrial Myocardium in Patients with Paroxysmal Atrial Fibrillation

Abstract

The process of aging and its effect on the histological appearance of the conduction system of the heart have been scantly described. It is not easy to attribute a certain condition to the aging process because it is often impossible to separate physiological aging from the development of pathological changes due to a concomitant disease. Nevertheless, the fact is that atrial fibrillation (AF) is a common arrhythmia in the elderly, and its incidence rise sharply with age. The increase in prevalence of AF in older persons has been reported to be associated with degeneration of the atrial muscle in pathological studies. Evidence in the human atrial muscle of age-related electrical uncoupling of the side-to-side connections between bundles, related to the proliferation of extensive collagenous tissue septa in intracellular spaces was clearly demonstrated. This translates into electrophysiological changes, hence prolonged and fractionated atrial electrograms are recorded from these areas during sinus rhythm by endocardial mapping of the atrium. These abnormal atrial electrograms are characteristics of paroxysmal AF and were found in a significantly greater proportion in older patients than in younger ones with AF. Advancing age is associated with atrial remodeling characterized by anatomical and structural changes, reductions in atrial voltage with discrete areas of fractionated and prolonged atrial endocardial electrograms, widespread conduction slowing as well as anatomically determined functional conduction delay and block. These electrophysiological changes within the atrial myocardium may be responsible substrate for the increased propensity to develop AF with increasing age.