Appearance of the interventricular septum in obstructive lesions of the left ventricular outflow tract.

Measurements of the thickness of the septum were made in 26 cardiac specimens and in 13 patients. There were 10 normal specimens, five with aortic stenosis, two with asymmetric septal hypertrophy, four with hypertensive cardiovascular disease, and five with idiopathic cardiomyopathy. Patient measurements were obtained by visualizing the septum during simultaneous left and right ventriculography on angiograms obtained in the left anterior oblique projection. Four patients were normal, five had aortic stenosis, and four had a symmetric septal hypertrophy. Measurements derived from normal cardiac specimens and angiographic appearance suggested that the normal septum is a smooth-walled structure with right and left ventricular surfaces parallel, diverging only slightly at the apex of the ventricle. In aortic stenosis and idiopathic cardiomyopathy, the septum tends to be biconvex with maximal thickening in its middle third. Hypertensive cardiovascular disease produces uniform septal thickening, resembling an exaggeration of normal. However, in asymmetric septal hypertrophy no consistent patterns of hypertrophy or septal thickening are evident; bulging can be present at any point along the left ventricular surface of the septum.