Aortic valve stenosis is a narrowing of the aortic valve between the lower left chamber of the heart and the aorta, which supplies blood to the body. A narrowed aortic valve forces the lower left chamber of the heart to pump harder to get enough blood through the valve.

Aortic valve stenosis can be caused by a structural problem called bicuspid aortic valve, which develops before a baby is born (congenital heart defect). In these cases, the valve has only two flaps, or leaflets, instead of the normal three.

Aortic valve stenosis also occurs as a person ages and the valve becomes hard and thick from calcium buildup. Most cases of aortic valve stenosis caused by calcium buildup occur in people who are older than 65.