W.: Pressure-flow studies in hypertrophic subaortic stenosis

outflow tract of the left ventricle might be ob-structed by an asynchronous contraction of the deep bulbo spiral muscle bundle. Brock described a clinical entity resulting from muscular obstruc-tion to the left ventricular outflow tract in 1957 (2). The pathological anatomy in eight such cases of muscular obstruction was presented by Teare in 1958 (3). Since these reports were published, there have been numerous studies dealing with the symptomatology, physical find-ings, and laboratory data in well-documented cases of hypertrophic subaortic stenosis (4-7). Although the exact nature of left ventricular ejection in these patients is unknown, Brachfeld and Gorlin postulated that the initial phase of cardiac ejection is relatively unencumbered and that the obstruction to outflow produced by the hypertrophied septal muscle occurs late in sys-tole (4). This concept was based primarily on pressure data, since the phasic aortic blood flow had not been measured. The pressure gradient technique provides a method whereby the in-stantaneous aortic blood flow can be estimated in the intact patient (8). The purpose of this re-port is to present the instantaneous blood flow and pressure obtained by this technique in the aorta of five patients with hypertrophic subaortic stenosis. Methods Five male patients were studied. The clinical (4), electrocardiographic (9), and roentgenographic (5) findings were consistent with the diagnosis of hyper-trophic subaortic stenosis. The diagnosis was confirmed in all patients by routine cardiac catheterization studies, including the demonstration of a significant pressur