Abstract
We describe an unusual case of spontaneously occurring intramural atrial hematoma with no communication with either atrium. The diagnosis of left atrial mass was made from transthoracic echocardiography. Subsequent examination with transesophageal echocardiography confirmed a large mass essentially filling the whole left atrium but failed to provide an etiologic diagnosis, which was eventually made at surgery. (J Am Soc Echocardiogr 1999;12:1101-3.)