Ultrasound in the Diagnosis and Evaluation of Therapy of Idiopathic Hypertrophic Subaortic Stenosis

Twenty patients with idiopathic hypertrophic subaortic stenosis (IHSS) were studied with cardiac echography. Eight of these patients were studied during left heart catheterization. The echographic pattern of mitral valve motion during systole was altered in a characteristic manner when hemodynamically significant left ventricular outflow obstruction was present in the eight patients studied at catheterization. The abnormal systolic pattern was abolished by spontaneous loss of outflow obstruction or loss of obstruction induced by beta-adrenergic blockade. An abnormal systolic mitral valve pattern was seen on the echogram in 17 of the 20 patients with proven IHSS. The abnormal pattern was lost after the institution of chronic propranolol therapy in one patient. The three patients not showing an abnormal systolic pattern were also taking propranolol. The pattern of mitral valve motion during diastole indicated an impaired rate of left ventricular filling. The basic abnormalities and variability in the degree of abnormality seen with echography of the left ventricular outflow tract are consistent with the proposed anatomy and pathophysiology of IHSS.