Echocardiographic assessment of discrete subaortic stenosis in childhood

The validity of Laplace's relation for assessing peak left ventricular pressure has previously been demonstrated in children with congenital aortic valve $\text{s}$tenosis by using the echocardiographically determined end-diastolic $\text{h}\text{r}$ ratio (that is, the ratio of mean left ventricular septal and posterior wall thicknesses to half the minor left ventricular cavity axis). This report examines the applicability of this ratio to the preoperatlve assessment of left ventricular pressure in 17 children with discrete subaortic stenosis. Because the regression equation derived from previously published data on patients with aortic valve stenosis and the present data on children with subaortic stenosis were similar, a pooled estimate of peak left ventricular pressure (LVP) in children $\text{w}$ith left ventricu$\text{l}$ar outflow tract obstruction is presented: $\text{LVP}\text{= 312.23 (}\text{h}\text{r}\text{) ± 28.01 (}\text{h}\text{r}\text{)}$.Additionally, the left ventricular outflow tract was measured as the anteroposterior dimension between the first recognizable closure point of the mitral valve and the interventricular septum and expressed as the left ventricular outflow tract/aortic root dimension ($\text{LVOT}\text{Ao}$) ratio. This ratio was tower in patients with subaortic stenosis than in control subjects and was helpful in differentiating patients with mild stenosis from those with more severe stenosis. The prevalence of echocardiographically observed features such as early systolic closure of the aortic valve and fluttering of the aortic valve leaflets could not be correl$\text{a}$ted with the severity of stenosis. It is concluded that the end-diastolic $\text{h}\text{r}$ ratio and the $\text{VOT}\text{Ao}$ ratio are quantitatively useful in the assessment of subaortic stenosis, whereas the commonly present motion abnormalities of the aortic valve are not indicative of the severity of the subaortic lesion.