The heart has four main valves that facilitate the pumping activity of the heart: - The tricuspid valve, between the right atrium and the right ventricle. - The pulmonary valve, between the right ventricle and the pulmonary artery. - The mitral valve, between the left atrium and the left ventricle. - The aortic valve, between the left ventricle and the aorta. Each valve consists of a set of flaps (also called "leaflets" or "cusps") that open and close to enable blood to flow in the correct direction. The function of the valves may be compromised by either congenital or acquired abnormalities. Damage to the valves can occur due to infection, rheumatic fever or aging. For example, the opening in a valve may narrow (a condition known as "stenosis"), meaning the heart has to work harder to get blood through the opening; this generates higher pressure within the heart and eventually causes the cardiac muscle to overdevelop. Another common valvular problem is incomplete closure, which allows the blood to flow backward through the valve (a condition known as "regurgitation"); this overloads the heart with blood, eventually resulting in enlargement (or "dilatation") of the heart's cavities. \nThe two most common valvular disorders in older adults are aortic stenosis and mitral regurgitation. The symptoms of valvular disorders vary depending on which valve is affected as well as on the type and severity of the change. Mild changes may cause no symptoms; a heart murmur — detected when the heart is examined with a stethoscope — is often the first sign of valve damage. In aortic stenosis, however, exertion can cause chest pain (known as "angina") or a feeling of tightness in the chest, shortness of breath, fainting or heart palpitations. Sudden death in otherwise healthy athletes is sometimes caused by aortic stenosis. Regurgitation can also cause detectable symptoms, such as shortness of breath or wheezing when lying down; these complaints may be intensified by exercise, increased resistance to breathing and immersion. Treatment for valvular disorders generally involves surgery. Defective valves may be either repaired or replaced by prosthetic valves. Preventing valvular damage is, of course, the best approach. Routine physical exams may uncover evidence of early valvular disease. In such cases, close, regular medical surveillance is advised to identify, and hopefully slow, progression of the damage.