Discrete subaortic valvular stenosis: the clinical utility and limitations of transesophageal echocardiography.

Transesophageal echocardiography (TEE) is a useful technique in the diagnosis and intraoperative assessment of discrete subaortic stenosis (DSS). It allows clear visualization of the subaortic membrane, which may be missed by transthoracic echocardiography, differentiates DSS from other causes of left ventricular outflow tract obstruction, and accurately detects the presence of associated aortic regurgitation and bacterial endocarditis. Limitations in its use include inadequate visualization of the left ventricular outflow tract by TEE in the presence of a prosthetic mitral valve or mitral annular calcification, and improper alignment of the Doppler cursor across the outflow tract.