Pathophysiology
Aortic Stenosis occurring during systole. The turbulence causing the murmur is being caused by obstruction of the blood flow during left ventricular ejection. The left ventricle hypertrophies to obtain normal flow during the valve. End-diastolic pressure will increase to achieve adequate filling of the ventricle. Systolic function is maintained despite the increasing overload but the ventricle will eventually become stiff and non-compliant.

The early progression may be slow, and is only regarded critical once the open valve area is reduced to less than 1 cm2 (about one-quarter its normal size). At this time peak systolic pressure has increased to a level above 50 mmHg to maintain normal flow, and symptoms may occur.