Subaortic stenosis (discrete form). Classification and angiocardiographic features.

The angiocardiographic features of 18 cases of discrete form subaortic stenosis (DSAS) are analyzed and four classifications defined: Type I, a thin membranous diaphragmatic stenosis; Type II, a fibrotic ring stenosis; Type III, a fibromuscular additional tissue stenosis; and Type IV, a tunnel-like stricture of the left ventricular outflow tract. This classification allows the distinction of DSAS from muscular hypertrophic stenosis with which it is often confused. Due to the concomitant finding of aortic insufficiency, the types of DSAS are better recognized if selective thoracic aortography as well as selective left ventriculography are performed.