Muscular Subaortic Stenosis

Two types of intraventricular pressure difference within the left ventricle of man are described. The first type was encountered in eight consecutive patients with muscular subaortic stenosis in whom the outflow tract pressure distal to the stenosis was low and equal to the aortic systolic pressure, whereas all ventricular pressures proximal to the stenosis, including that just inside the mitral valve (the initial inflow tract pressure) were high. The second type was encountered in five of 10 patients with nonobstructive cardiomyopathy when a cardiac catheter was advanced to the left ventricular wall where it became entrapped or imbedded in cardiac muscle in systole and recorded a high ventricular pressure that was believed to reflect subendocardial intramyocardial tissue pressure. In this second type of intraventricular pressure difference, the initial inflow tract pressure, as well as all truly intracavitary pressures, were low and equal to the aortic systolic pressure. By defining two types of intraventricular pressure difference, the recent controversy as to the nature of such pressure differences in man may be resolved, and the obstructive nature of muscular subaortic stenosis reaffirmed.