[Cerebral embolism due to left atrial ball thrombus without mitral stenosis--usefulness of the transesophageal echocardiography for the diagnosis].

We reported two cases of cerebral embolism associated with atrial fibrillation. Left atrial ball thrombus without mitral stenosis was diagnosed by the transesophageal echocardiography, followed by successful removal. Left atrial ball thrombus has a risk for lethal complications, and a high incidence of systemic embolism even during anticoagulation therapy. An immediate surgical treatment is needed. The transthoracic echocardiography is not useful in diagnosis for left atrial ball thrombus. It is important to examine left atrial ball thrombus by the transesophageal echocardiography in patients with cerebral embolism associated with atrial fibrillation.