Echocardiography in Coexisting Hypertrophic Subaortic Stenosis and Fixed Left Ventricular Outflow Obstruction

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Abstract
Echocardiographic study was done on four pediatric patients with coexisting hypertrophic subaortic stenosis (HSS) and fixed left ventricular outflow (LVO) obstruction. One had valvar aortic stenosis, two had discrete subaortic stenosis and one had coarctation of the aorta. Preoperatively, HSS was not suspected in any of these patients because of the classical findings of fixed LVO obstruction. The echocardiographic examination revealed an abnormal systolic anterior movement (SAM) of the anterior mitral leaflet with ventricular septal hypertrophy in all, but these findings were overlooked or thought to be related to a subvalvar diaphragm. One or two years after the surgical removal of their fixed obstruction, all showed clinical pictures of HSS. Postoperative echocardiographic examination showed an abnormal SAM with asymmetrical septal hypertrophy, and cardiac catheterization revealed mild to severe degrees of resting pressure gradients across LVO tracts. Amyl nitrite inhalation produced a more prominent SAM with increasing pressure gradient, and angiotensin infusion abolished the SAM and reduced the pressure gradient. From our present study, echocardiography has the potential for identification of HSS coexisting with a fixed LVO obstruction. We recommend that all patients with LVO obstruction have an echocardiographic examination along with pharmacological testing. The demonstration of an unusually thickened ventricular septum and especially, abnormal SAM of the mitral valve would require careful evaluation of left heart hemodynamics and the determination of the level of the major obstruction during cardiac catheterization for pre and postoperative management.