More than 1.5 million people in the U.S. have aortic stenosis, and about 500,000 of them have severe aortic stenosis. In fact, aortic valve disease is one of the two most common types of valve disease. Many people with aortic stenosis have no symptoms. Aortic stenosis is when the leaflets of the aortic valve become stiff and the opening becomes narrow making it harder for the heart to pump blood to the body.