Enlargement of the Excluded Left Atrial Appendage With Thrombus.

We report progressive enlargement of the excluded left atrial appendage (LAA) with a thrombus in a patient who had undergone valve surgery and endocardial suture closure of the LAA previously. Echocardiography and CT detected no communication between the LAA and the left atrium. Magnetic resonance imaging showed the LAA was filled with fresh and old thrombi. Coronary arteriography demonstrated small left coronary artery-LAA fistulae. At surgery, successful exclusion of the LAA was confirmed after removal of the thrombi. Persistent inflow of blood through the coronary artery fistulae to the excluded LAA may be the primary mechanism of this pathology.