[Four successfully operated cases of ball thrombus in the left atrium].

The authors report four cases of the left atrial ball thrombus associated with mitral stenosis. Three of four which had floating ball thrombus in the left atrium presented with syncopal attacks and systemic embolism. Echocardiography was the most effective method for preoperative diagnosis of ball thrombus in the left atrium and mitralstenosis. After having accurate diagnosis of ball thrombus in the left atrium by echocardiogram, all of cases were treated urgently with removal of the thrombus and mitral valve replacement or mitral commissurotomy. During operation, the head down position and slight right lateral position had been maintained to prevent the impaction of the ball thrombus into mitral valve orifice and the immediate cardiopulmonary bypass by ascending aortic, superior and inferior venous cannulation were placed through midsternal splitting incision. Because of high frequency of peripheral embolism and sudden death, left atrial ball thrombus should be recommended to be removed urgently.