Echocardiographic assessment of the severity of aortic stenosis in children and adolescents.

The magnitude of ventricular hypertrophy in response to afterloading is determined by wall stress, with wall thickness increasing in proportion to ventricular load until systolic wall stress is normalized. With use of echocardiographic measurements of left ventricular end-systolic wall thickness (Ws) and cavity transverse dimension (Ds), the pressure constant k was calculated in 16 patients without left heart obstruction according to the formula k = P-Ds/Ws. The mean value for k was 225 +/- 6.7 (standard deviation) mm Hg. From this value, left ventricular pressure was estimated in 13 patients with aortic stenosis aged 4 to 17 years using the formula P = k-Ws/Ds. No subject had evidence of cardiac failure. Peak systolic aortic pressure difference (delta P) was calculated by subtracting cuff-measured brachial arterial peak systolic pressure from the estimated left ventricular pressure. Excellent correlation was obtained between the estimated delta P and that found at cardiac catheterization (r = 0.89). In two patients, echocardiographic data predicted significant obstruction in the presence of normal electrocardiographic, vectorcardiographic and vector lead tracings. Echocardiography offers a noninvasive method for estimating the severity of aortic stenosis, in the absence of myocardial failure; it appears to be more sensitive than other currently employed techniques.