Causes

Your heart has four valves that keep blood flowing in the correct direction. These valves include the mitral valve, tricuspid valve, pulmonary valve and aortic valve. Each valve has flaps (cusps or leaflets) that open and close once during each heartbeat. Sometimes, the valves don't open or close properly. If a valve doesn't fully open or close, blood flow is reduced or blocked.

In aortic valve stenosis, the aortic valve between the lower left heart chamber (left ventricle) and the aorta does not open completely. The area through which blood moves out of the heart to the aorta is narrowed (stenosis).

When the aortic valve opening is narrowed, your heart must work harder to pump enough blood into the aorta and to the rest of your body. The extra work of the heart can cause the left ventricle to thicken and enlarge. Eventually the strain can cause a weakened heart muscle and can ultimately lead to heart failure and other serious problems.

Aortic valve stenosis causes include:

• Congenital heart defect. Some children are born with an aortic valve that has only two cusps (bicuspid aortic valve) instead of three (tricuspid aortic valve). Rarely, an aortic valve may have one (unicuspid) or four (quadricuspid) cusps.

  Having a congenital heart defect such as a bicuspid aortic valve requires regular checkups by a doctor. The valve defect may not cause any problems until adulthood. If the valve begins to narrow or leak, it may need to be repaired or replaced.

• Calcium buildup on the valve. Calcium is a mineral found in your blood. As blood repeatedly flows over the aortic valve, calcium deposits can build up on the heart valves (aortic valve calcification).

  The calcium deposits may never cause any problems. Aortic valve stenosis that's related to increasing age and calcium deposit buildup usually doesn't cause symptoms until ages 70 or 80. However, in some people — particularly those with a congenital aortic valve defect — calcium deposits result in stiffening of the valve cusps at a younger age.

  Heart valve calcium deposits aren't linked to taking calcium tablets or drinking calcium-fortified products.

• Rheumatic fever. This complication of strep throat infection may result in scar tissue forming on the aortic valve. Scar tissue can narrow the aortic valve opening or create a rough surface on which calcium deposits can collect.

  Rheumatic fever may damage more than one heart valve, and in more than one way. While rheumatic fever is rare in the United States, some older adults had rheumatic fever as children.