Types of Aortic Stenosis: Obstruction to left ventricular outflow is commonly at the valvar level. Less commonly it is at the sub valvar or supra valvar level. Sub valvar obstruction could be discrete as in a fibromuscular septum type or tunnel stenosis or hypertrophic obstructive cardiomyopathy (HOCM). Valvar aortic stenosis may be of congenital, rheumatic or degenerative aetiology.