Atrial septal defects (ASDs) are the most common congenital cardiac abnormalities in adults. Patients frequently present with symptoms for the first time at adult age. One of the most common late complications of an ASD is the development of atrial tachyarrhythmias (ATs), especially atrial fibrillation (AF). In a large population-based study from Ontario, the prevalence of AT was 19% in adult patients with ASD, which is fourfold higher than that in the general population.1 The incidence of AT continues to increase with age.2 ,3 This vulnerability to AT is not surprising considering the long-standing haemodynamic derangements due to left-to-right shunting causing atrial stretch, RV dilatation, elevated pulmonary arterial pressure and atrioventricular valve regurgitation. The resultant atrial electrical remodelling with increased dispersion of atrial refractoriness may predispose to AT. Furthermore, in surgically corrected patients, the presence of patches and suture lines may create the substrate for macroreentry AT.

The current guidelines recommend closure of an ASD when there are signs of RV volume overload (in the absence of pulmonary hypertension) or if there is a suspicion of paradoxical embolism. In earlier studies, the prevalence of prior AT at the time of surgical closure at adult age is approximately 20%.2 ,3 ASD closure is associated with reduction in right atrial and ventricular volume and an increase in RVEF. However, atrial electrical and structural remodelling …