Echocardiographic Assessment of Idiopathic Hypertrophic Subaortic Stenosis

¹ Section of Cardiovascular Medicine, Departments of Medicine and Physiology, University of California, School of Medicine, Davis, Calif.; Section of Cardiovascular Diseases, Departments of Medicine and Surgery, University of Kansas Medical Center, Kansas City, Kans

Echocardiography provides a reliable, sensitive and practical noninvasive means for the accurate diagnosis of idiopathic hypertrophic subaortic stenosis (IHSS) and the sequential assessment of severity of left ventricular outflow obstruction in the management of this condition. The principal echocardiographic features of IHSS have been demonstrated to include: (1) anterior displacement of the anterior mitral valve in midejection; (2) asymmetric ventricular septal hypertrophy; (3) anterior position of the mitral valve at the onset of systole; (4) forward systolic movement of the posterior mitral leaflet; (5) reduced rate of anterior mitral valve closure in diastole; and (6) partial closure of the aortic leaflets in midejection. The characteristic abnormalities of anterior systolic leaflet motion observed on mitral valve echogram and the response of the leaflet to provocative maneuvers and surgical treatment strongly support the importance of the role of obstruction in IHSS and the apposition of the anterior mitral leaflet, with the hypertrophied ventricular septum as the site of subaortic stenosis.