Left atrial ball thrombus in a patient without mitral valve disease.

We experienced a large left atrial ball thrombus in a patient without mitral valve disease. By transthoracic echocardiography the mass was appeared to be free-floating and swinging randomly in the left atrium. An urgent operation was performed successfully. Operative findings revealed the mass to be a large ball thrombus loosely attached to atrial wall. We suggest that surgical removal is indicated as soon as possible, because of a very high risk of embolism or circulatory collapse.