Aortic Stenosis: Definition

AS is defined as a restricted opening of the valve cusps causing an obstruction to left ventricular (LV) outflow.

LV outflow obstruction can also be produced by a congenital abnormality above the valve (supra-valvular aortic stenosis) or by sub-valvular obstruction due to muscular hypertrophy as seen in hypertrophic cardiomyopathy.

AS is severe once the valve area has decreased to 1cm2 or less (normal 3-4cm2).