Aortic valve stenosis is a aortic valve disease caused by the incomplete opening of the aortic valve. The aortic valve controls the direction of blood flow from the left ventricle to the aorta. When in good working order, the aortic valve does not impede the flow of blood between these two spaces. Under some circumstances, the aortic valve becomes narrower than normal, impeding the flow of blood. This is known as aortic valve stenosis, or aortic stenosis, often abbreviated as AS. The disease is Experimental Factor Ontology entry EFO_0000266 (aortic stenosis). Also known as: AS, AS - Aortic stenosis, Aortic Valve Stenoses, Aortic Valve Stenosis, Aortic valve stenosis (disorder), Aortic valve stenosis, NOS, Stenosed aortic valve, Stenoses, Aortic.