Unusual cause of recurrent syncope in a child.

A 5-year-old boy with an unremarkable past medical and family history presented with recurrent syncope precipitated by physical activity. Electrocardiogram performed in the emergency room after one of his episodes revealed atrial flutter. He had a structurally normal heart. Exercise stress test revealed atrial fibrillation with rapid ventricular response immediately on commencement of running. Atrial fibrillation subsequently organized into atrial flutter with variable ventricular response followed by spontaneous conversion to sinus rhythm. This case highlights the use of exercise stress test in a preschool child to elicit an unusual cause of syncope.