Angiographic Anatomy of the Left Ventricle and Mitral Valve in Idiopathic Hypertrophic Subaortic Stenosis

The angiographic features of the left ventricle were examined in patients with idiopathic hypertrophic subaortic stenosis who had clinical and hemodynamic evidence of obstruction. Of 36 combined hemodynamic and angiographic studies considered to be technically satisfactory, 33 showed a characteristic combination of abnormalities. In the frontal projection in systole, a linear radiolucent area extended across the left ventricular outflow tract 2 to 2.5 cm below the aortic annulus, at a level corresponding to the site of intraventricular pressure change. In the left oblique and lateral projections, the mitral leaflets did not swing posteriorly in a normal fashion, but projected into the outflow tract during mid and late systole. The radiolucent line, seen in the frontal views, was considered to represent contact of the leading edge of the leaflet with the hypertrophied muscular interventricular septum. The jet of mitral regurgitation, when present, was seen immediately below the anterior mitral leaflet. Severe hypertrophy was also seen to involve the inferior portion of the muscular septum, causing displacement of the papillary muscles superiorly and to the left. This maldirection of the papillary muscles was postulated to cause abnormal traction on the chordae tendineae and to prevent normal movement of the mitral leaflets away from the septum during systole. The leaflets, held in the outflow tract, form the posterior component of the obstruction, the anterolateral component of which results from severe, asymmetric septal hypertrophy. It was proposed that this mechanism plays an important part in producing the intraventricular pressure gradient in many patients with idiopathic hypertrophic subaortic stenosis.