Cross-sectional echocardiographic localization of sites of left ventricular outflow tract obstruction

Real time two-dimensional echocardiographic studies of left ventricular outflow tract cross-sectional anatomy were obtained by the multicrystal echocardiographic method (Bom system) in 35 patients with various types of outflow obstruction as delineated by clinical, hemodynamic and angiographic studies. In each patient the noninvasive test allowed prediction of the site of obstruction. In valvular aortic stenosis, echocardiographic diagnostic findings included poststenotic dilatation of the ascending aorta, thickened aortic cusp tissue and increased superior-inferior cusp excursion (doming). The site of supravalvular aortic stenosis was readily observed although echocardiographic findings often underestimated the degree of obstruction recorded at cardiac catheterization. In patients with discrete subvalvular aortic stenosis, the major finding was a localized thickening of the septum and anterior mitral anulus producing a narrowing of the left ventricular outflow tract that was present in diastole and persisted throughout the cardiac cycle. The combination of discrete subvalvular and valvular aortic stenosis could be identified as well as mitral valve abnormalities associated with left ventricular outflow tract obstruction. Asymmetric septal hypertrophy and systolic anterior motion of the mitral leaflets were noted in six patients with idiopathic hypertrophic subaortic stenosis. This new echocardiographic approach allowed accurate localization of the site of left ventricular outflow tract obstruction and detection of associated malformations. The method has substantial merit as an initial test to establish diagnosis and allows more appropriate planning of a subsequent hemodynamic study.