Echocardiographic features of a mycotic aneurysm of the left ventricular outflow tract caused by perforation of mitral-aortic intervalvular fibrosa.

We present the apparently unique M-mode and two-dimensional echocardiographic features of a surgically confirmed pseudoaneurysm of the left ventricular outflow tract, which probably developed as a result of perforation of the mitral-aortic intervalvular fibrosa. Echocardiographic studies revealed an aneurysmal sac situated between the aortic root and the left atrium. The aneurysm expanded in systole and collapsed or emptied in diastole, suggesting direct communication with the left ventricle. Such an aneurysm must be differentiated from various pathologic findings of the aortic root. The location and characteristic motion during the cardiac cycle should alert the clinician to the correct diagnosis of such an aneurysm.