The dangerous fifth chamber: congenital left atrial appendage aneurysm.

Aneurysms of the left atrial appendage are extremely rare. Enlargement of the left atrial appendage can be congenital or acquired. Dysplasia of the left atrial muscles leads to congenital left atrial appendage aneurysm and usually presents as atrial tachyarrhythmia or embolic events in the second or third decade of life. We report a case of an asymptomatic 12-year-old child with a congenital left atrial appendage aneurysm. Transthoracic and transoesophageal echocardiography demonstrated a large left atrial appendage aneurysm without thrombus or spontaneous echo-contrast. The patient was successfully treated with surgical resection of the aneurysm.