Aortic stenosis is a narrowing (stenosis) of the heart valve between the left ventricle of the heart and the aorta. This impedes the delivery of blood through the aorta to the body. A normal aortic valve has three leaflets or cusps, but a stenotic valve may have only one cusp (unicuspid) or two cusps (bicuspid), which are thick, stiff and stenotic. Some children with aortic stenosis have chest pain, unusual fatigue, dizziness or fainting. Many children have few or no symptoms. Treatment is usually surgical.