Atrial myocardial pathoelectrophysiology in adults with a secundum atrial septal defect is unaffected by closure of the defect. A study using high resolution signal-averaged orthogonal P-wave technique

Atrial conduction disturbances in middle-aged patients with ASD, manifested as a prolonged P-wave duration, do not change after ASD closure and are not related to the dilatation of the right and left atria. It is suggestive that atrial conduction disturbance associated with ASD develop early and early intervention is required to prevent the development of late atrial fibrillation.