Atrial arrhythmias complicate the clinical course of adult patients with an atrial septal defect. Atrial flutter is more prevalent in younger patients, and frequently regresses after surgical defect closure. Atrial fibrillation however, which results from a chronic underlying disease, rarely reverts to sinus rhythm after surgical repair. While younger patients with atrial flutter clearly benefit from defect closure alone, this is not evident in older patients with fibrillation, who may need an additional anti-arrhythmic procedure concomitant to defect closure.