The aorta is the main artery leaving the heart. When blood leaves the heart, it flows from the lower chamber (the left ventricle), through the aortic valve, into the aorta. In aortic stenosis, the aortic valve does not open fully. This restricts blood flow.

As the aortic valve becomes more narrow, the pressure increases inside the left heart ventricle. This causes the left heart ventricle to become thicker, which decreases blood flow and can lead to chest pain. As the pressure continues to rise, blood may back up into the lungs, and you may feel short of breath. Severe forms of aortic stenosis prevent enough blood from reaching the brain and rest of the body. This can cause lightheadedness and fainting.

Aortic stenosis may be present from birth (congenital), or it may develop later in life (acquired). Children with aortic stenosis may have other congenital conditions.

In adults, aortic stenosis occurs most commonly in those who've had rheumatic fever, a condition that may develop after strep throat or scarlet fever. Valve problems do not develop for 5 - 10 years after rheumatic fever occurs. Rheumatic fever is increasingly rare in the United States.

Only rarely do other factors lead to aortic stenosis in adults. These include calcium deposits forming around the aortic valve, radiation treatment to the chest, and some medications.

Aortic stenosis is not common. It occurs more often in men than in women.