[Ball thrombus in the right atrium: report of a case].

: A 63-year-old man visited our hospital because of intermittent claudication due to an embolic episode in the left femoral artery. He had a long history of arterial fibrillation but had received no anticoagulant therapy. Echocardiography showed a large floating ball-shaped shadow in the right atrium, without any sign of tricuspid stenosis. Pulmonary perfusion scintigram was normal. At the operation, the thrombus which attached to the superior atrial septum with a thin string was removed. The thrombus was 54 x 40 x 25 mm in size and 23.8 g in weight, whose cut surface was in layers. There was neither atrial septal defect nor foramen ovale to suggest possibility of paradoxical embolism. The postoperative course was uneventful and he was discharged on the 9th postoperative day. Although the mechanism of the thrombus formations is unknown, it is considered to be important to continue anticoagulant therapy to avoid reccurence of intracardiac thrombus.