Left atrial bacterial mural endocarditis. An unusual case of Staphylococcus aureus endocarditis confined to the mural left atrium is presented. Echocardiographic studies revealed a 1.5 x 2.0-cm vegetation mimicking a myxoma situated in the path of a mitral regurgitant jet on a color Doppler test. Emboli to upper and lower extremities and brain complicated the patient's preoperative course. Surgical excision and pathologic examination confirmed this rare occurrence. 