Transesophageal echocardiography in the diagnosis of left atrial appendage aneurysm. Intrapericardial left atrial appendage aneurysm is rare. We describe the transthoracic and transesophageal echocardiographic findings in a 42-year-old man with atrial arrhythmia and an abnormal left atrial appendage on chest roentgenogram. Presence of an intrapericardial left atrial appendage aneurysm was confirmed at surgery. 