MONDO_0042981 (aortic valve stenosis) (AVS) is a condition characterized by narrowing of the heart's aortic valve opening. This narrowing prevents the valve from opening fully, which obstructs blood flow from the heart into the aorta, and onward to the rest of the body. AVS can range from mild to severe. Signs and symptoms typically develop when the narrowing of the opening is severe and may include chest pain (angina) or tightness; shortness of breath or fatigue (especially during exertion); feeling faint or fainting; heart palpitations; and heart murmur. Individuals with less severe congenital AVS (present at birth) may not develop symptoms until adulthood. Individuals with severe cases may faint without warning. AVS can have several causes including abnormal development before birth (such as having 1 or 2 valve leaflets instead of 3); calcium build-up on the valve in adulthood; and rheumatic fever. Also known as: AS, aortic stenosis.