What would be the forward and backward effects of aortic stenosis?

Several: The heart must push harder which is a strain and causes "muscle bound" left ventricular hypertrophy and later heart failure. The muscle needs more oxygen to pump and coronary flow is interfered with causing angina or heart attack in some. Low forward flow can lead to fainting syncope. It is related to degree if stenosis- narrowing of this door! think of it as a door which does not open fully.