Introduction: Atrial septal defect (ASD), mostly type II, often remains undetected until adulthood and may contribute to atrial fibrillation (AF) onset. Percutaneous ASD closure is the method of choice if there is enough margin (4-5 mm) for the „umbrella” implantation, particularly in the elderly, otherwise surgical closure is advised. Sinus rhythm frequently reappears within a few months after closing. (1-3) We present four such patients.

Case reports: Case 1. 67-years-old lady underwent catheter ablation for AF with tachyarrhythmia. At the same time ASD was detected and surgically closed. During the follow-up period her sinus rhythm is maintained with good cardiorespiratory function. Case 2. In 66-years-old lady paroxysmal AF was recurrently drug-converted to sinus rhythm. Eventually ASD type II was diagnosed and percutaneously occluded. The follow-up visits confirm stable sinus rhythm with excellent clinical outcome.Case 3. 59-years-old patient had recurrent paroxysms of AF in 2013. At that time ASD was detected and percutaneously closed. Three weeks later because of atrial undulation he underwent successful electrocardioversion and from that time on she maintains stable sinus rhythm. Case 4. Since 2007 a 59-years-old hypertensive patient is enduring paroxysmal AF attacks; in 2011 he underwent transvenous occlusion of recently diagnosed ASD followed by stable sinus rhythm for 6 months, when an AF relapse was successfully electrocardioverted. Nevertheless, five years later ensued permanent AF.

Conclusion: ASD discovered in adulthood is often associated with AF. After its closure a stable sinus rhythm may often be achieved.