Congenital left atrial appendage aneurysm diagnosed by fetal echocardiography

A newborn infant was evaluated because of a large cystic mass adjacent to the left atrium on prenatal ultrasound. The diagnosis was an aneurysm of the left atrial appendage. Most cases of this rare lesion are recognized between the 2nd and 4th decades of life. The present case, however, was detected on fetal echocardiography. The patient showed significant mitral regurgitation caused by the compression of the left atrioventricular groove. Simple aneurysmectomy without mitral valvuloplasty was sufficient to relieve significant mitral regurgitation in this case.