DIAGNOSTIC METHODS VALVULAR HEART DISEASE Prediction of the severity of left ventricular outflow tract obstruction by quantitative two-dimensional echocardiographic Doppler studies

In this study we explored the use of continuous wave Doppler echocardiography guided by simultaneous two-dimensional echocardiographic imaging as a method for noninvasively estimating pressure gradients in patients with discrete forms of left ventricular outflow tract obstruction. We studied 16 children, ages 6 months to 17 years, with valvular aortic stenosis (n = 12) or with discrete subaortic stenosis (n = 4) and compared maximal Doppler velocities in the aorta with pressure gradients obtained at cardiac catheterization. Examinations could be performed from the suprastemal notch view or from the apical left ventricular outflow tract view with equal accuracy for the study of flow in the left ventricular outflow tract, and results were comparable in both views. With a simplified Bernoulli relationship (gradient = 4 x [maximal velocity12), results suggested that Doppler echocardiography could be used to predict the severity of obstruction in our patients with a correlation coefficient of r = .94 (SEE + 7.5 mm Hg) between Doppler-estimated gradients and gradients obtained at catheterization. The method appears promising for initial evaluation and for serial management of patients with discrete forms of left ventricular outflow tract obstruction. Circulation 68, No. 2, 348-354, 1983. THE CLINICAL DIAGNOSIS of aortic stenosis in children is usually not difficult. However, clinical estimation of severity of left ventricular outflow tract obstruction is sometimes difficult. ' Because several forms of left ventricular outflow tract obstruction in childhood can follow a progressive course in the absence of clinical changes,2 a method for noninvasive estimation of severity would be very useful. Noninvasive diagnostic methods such as electrocardiography and especially electrocardiography performed during exercise3 are of some value in detecting patients at risk for significant aortic stenosis but do not quantify the severity of aortic stenosis. Several echocardiographic studies"7 have suggested M mode and two-dimensional echocardiographic methods to quantify the degree of obstruction of the left ventricular outflow tract at both valvular and subvalvular levels, but none of these methods has proved From the Department of Pediatrics, University of Arizona, Health Sciences Center, Tucson, and the Departamento de Cardiologia, Casa de Saude Campinas, Campinas, Sao Paulo, Brazil. Address for correspondence: David J. Sahn, M.D., Department of Pediatrics (Pediatric Cardiology), University of California, San Diego, University Hospital CTF B 102, 225 W. Dickinson St., San Diego, CA 92103. Received Jan. 18, 1983; revision accepted April 7, 1983. 348 to be highly accurate, especially in patients after surgery. However, in preliminary studies Doppler echocardiography has been shown to be a promising technique for quantifying the severity of stenotic valvular lesions.'"2 With the simplified Bernoulli equation, both Holen et al.9 and Hatle et al.'I'2 showed that a Doppler echocardiographic method could be used to relate peak flow velocities (measured in the jet distal to stenotic mitral or aortic valve orifices) to transvalvular gradients (measured at cardiac catheterization). The purpose of this prospective study was to assess the capability and accuracy of a two-dimensional echocardiographic Doppler method to predict the severity of discrete subvalvular or valvular aortic stenosis in children by providing a noninvasively derived estimate of hemodynamic gradient measured in patients at rest.