Pulmonary embolism due to right atrial free-floating thrombus during echocardiographic examination: a case of a pulmonary saddle thrombus.

A 69-year-old female with polymyositis was referred to our hospital with a chief complaint of dyspnea. Transthoracic echocardiography showed right ventricular overloading. In addition to two-dimensional echocardiography, observation of the abnormal free-floating string-like mass by three-dimensional echocardiography provided superior visualization of the features of the mass which protruded into the right ventricle across the tricuspid valve during diastole. These findings enabled us to confirm the diagnosis of venous thrombus. The thrombus disappeared during the echocardiographic examination. Multidetector-row computed tomography showed a string-like thrombus across the bifurcation of the main pulmonary artery. Anticoagulation therapy was initiated with heparin and warfarin, and fondaparinux was started on the fourth day. Three-dimensional echocardiography was useful in characterizing the motion and extent of the thrombus.