Idiopathic hypertrophic subaortic stenosis. I. Interventricular septum during the systolic contraction

Biplane left ventricular cineangiographies in 4 patients with typical obstructive idiopathic hypertrophic subaortic stenosis (IHSS) and in control patients with normal left ventricles were analysed. In the protruding hypertrophic muscular interventricular septum of IHSS a markedly reduced shortening occurs in either direction during the systolic contraction. It does not bend towards the right ventricle. It is suggested that the septum of IHSS acts as a suspender during the systolic contraction, thereby accounting for the fast stroke volume ejection and the high ejection fraction of IHSS.