Atrial septal defect presenting as atrial flutter in early infancy.

Atrial septal defects (ASD) may lead to supraventricular arrhythmias, notably atrial flutter and fibrillation, as a consequence of right atrial volume overload resulting from left-to-right shunting, which alters the electrophysiological properties of the right atrium. While ASDs can be associated with atrial flutter, its manifestation in infancy is exceedingly uncommon. We present the case of an infant with ostium secundum ASD who developed atrial flutter, successfully treated with direct current cardioversion.