The mitral valve regulates the ?ow of blood from the left atrium to the left ventricle, the main pumping chamber that pumps blood out into the arteries. It is composed of two lea?ets supported by a ?ne structure of stringlike tissues attached to the heart muscles. The mitral valve may be affected by prolapse, regurgitation, or stenosis.
Mitral Valve Prolapse
About 2 percent of the U.S. population have mitral valve prolapse, meaning that one or both of the ?aps of the mitral valve are enlarged and the supporting muscles are too long. As a result, the lea?ets do not close tightly and they billow into the atrium as the left ventricle con- tracts. Sometimes a small amount of blood leaks back into the atrium (regurgitation). Although there may be a variety of causes, many forms of prolapse are probably inherited. It occurs more frequently in women than men, often in very slender people who may have minor chest wall irregularities or scoliosis (a curvature of the spine). But it may be more severe in men.
In the vast majority of people, mitral valve prolapse is completely harmless and does not cause any long-term problems. Some people experience symptoms and seek treatment for them; symptoms include chest pain, palpitations (the sensation of feeling the heart beat), an irregular heartbeat, fatigue, shortness of breath when lying down, trou- ble breathing after exercise, or coughing.
Your doctor may detect mitral valve prolapse when listening to your heart through a stethoscope, because the billowing lea?ets can cause a characteristic click, followed by a murmur. If necessary, he or she can con?rm the diagnosis with an echocardiogram and assess the degree of regurgitation.
If you have little or no regurgitation and an otherwise normal heart, you will not need treatment. But if signi?cant regurgitation develops, or if other illness is present, you may be at risk of a serious problem, infec- tion of the valve.
Symptoms of mitral valve prolapse may improve with regular exer- cise, a decrease in caffeine consumption, and adequate ?uids. Or you may be prescribed beta-blockers to alleviate symptoms such as palpitations.
Mitral Valve Regurgitation
A mitral valve that fails to close completely when the powerful left ventricle contracts allows blood to “regurgitate” back into the atrium, undermining the one-way flow. Mitral valve regurgitation may be caused by damage to the valve from rheumatic fever , infective endocarditis , or a heart attack that damages the part of the muscle attached to the valve. The regurgitation can also result from enlargement of the left ventricle, possibly brought on by coronary artery disease or untreated high blood pressure, which stretches the perimeter of the mitral valve so that the lea?ets do not close completely.
Many people have no symptoms; in others, symptoms develop over a period of years because the heart compensates for the problem. But over time, the extra effort can cause the left ventricle to enlarge or pres- sure to build up in the lungs as the blood leaks backward. The symp- toms of regurgitation may come on slowly and can include shortness of breath or rapid breathing, fatigue, heart palpitations, or cough.
To relieve the symptoms of mitral valve regurgitation, your doctor may prescribe medications to lower your blood pressure or diuretics to rid your body of excess ?uids. He or she may also recom- mend that you take antibiotics before some dental or surgical proce- dures to prevent infection of the valve.
If surgery is necessary to restore valve function, your doctor will time the surgery carefully to be sure that your heart muscle does not become too weak to withstand the operation. The surgeon will repair your valve if possible, but in some people, an arti?cial valve is the best solution . After surgery, the long-term outlook for most people is very good.
Mitral Valve Stenosis
Mitral valve stenosis is a narrowing of the mitral valve. The narrowing or obstruction causes an increase in the pressure behind the valve in the left atrium. In most people, this type of damage to the valve was caused by a case of rheumatic fever in childhood . Because the use of antibiotics has dramatically decreased the occurrence of rheu- matic fever, mitral valve stenosis is becoming rare in the United States. It may occasionally occur in older people as a result of calcium deposits on the perimeter of the mitral valve, combined with the degenerative aging process that affects the tissues of the heart.
Many people with mild mitral valve stenosis do not experience symptoms, and treatment is not required. If the condition does cause symptoms to develop, they may develop slowly. Symptoms may include trouble breathing at night or after exercise; coughing, perhaps with traces of blood; fatigue; or chest pain that gets worse with exertion. There is risk of abnormal heart rhythms in the left atrium (atrial ?bril- lation), which can cause blood clots to form in the heart. The clots can dislodge and travel to the brain, increasing your risk of stroke.
A person with mitral valve stenosis may need to take antibiotics before undergoing certain medical or dental procedures to prevent infective endocarditis (see page 192) in the valve. Medication to slow the heart rate may help some people feel better. In some people with moderate stenosis, a balloon valvuloplasty (a procedure to open the valve with a balloon; ) may be an option. For a person with a severely diseased valve, particularly an older person, surgical repair or replacement of the valve may be necessary.
Aortic Valve Disease
The aortic valve, which has three crescent-shaped cusps (lea?ets), regu- lates blood ?ow from the left ventricle into the aorta, where it then cir- culates to the rest of the body . Either stenosis (narrowing) or regurgitation (backward leakage) can disrupt the blood ?ow. The valve can be damaged by rheumatic fever or infection. But some people are born with a bicuspid aortic valve—a valve with two lea?ets instead of three. A bicuspid valve may be less ef?cient and more prone to infection or calci?cation with aging. The aorta may be abnormal, too, in people with bicuspid aortic valves, regardless of the severity of the valve disease.
Aortic Valve Regurgitation
When an aortic valve does not close completely, blood leaks or regur- gitates back into the left ventricle. The condition occurs more com- monly in men, often between the ages of 30 and 60. The most typical causes of mild regurgitation are structural abnormalities of the valve (such as a bicuspid valve), damage from rheumatic fever, high blood
pressure, or calci?cation on the valve as a result of aging. In the most serious cases, the valve may suddenly start leaking as a result of infective endocarditis that actually makes holes in the lea?ets or from a tear or severing of the aorta above the valve.
As with other heart valve problems, a person may not experience symptoms for years. But if the regurgitation forces the left ventricle to work harder over a long period, it may enlarge. Left untreated, irreparable damage to the left ventricle—the heart’s main pumping chamber—could take place.
Symptoms, if or when they occur, include shortness of breath, chest pain with exercise, swelling in the ankles, fatigue, and a rapid pulse. Even if you do not have symptoms, your doctor may detect aortic regurgitation by listening to your heart sounds through a stethoscope. He or she will con?rm the diagnosis and assess your heart function with tests, including a chest X-ray, echocardiogram , and elec- trocardiogram . You may be advised to take antibiotics before some dental and surgical procedures to prevent endocarditis. Medications to treat high blood pressure and reduce the heart’s workload may help reduce symptoms. Your doctor will evaluate you periodically by monitoring changes in your symptoms, your phys- ical examinations, and tests such as echocardiograms.
Your doctor may recommend surgery to replace the aortic valve (see page 206) and limit damage to the heart muscle. As with surgery for mitral regurgitation, the procedure will be carefully timed to correct the problem before the heart is substantially weakened. If the problem is corrected before damage occurs, you are very likely to be able to return to a normal lifestyle.
Aortic Stenosis
If your aortic valve (which regulates the blood ?ow between your left ventricle into the aorta) becomes narrowed, your heart must work harder to force blood through the valve. As a result, the left ventricle enlarges and thickens. Over time, the heart may be unable to maintain the workload, and ?uid may back up in the lungs.
Today the most common cause of aortic stenosis is a degeneration of the valve that occurs with aging. Calcium, a mineral found in the blood, can build up on the valve over the course of your lifetime. Some calci?- cation may not cause any trouble, but in some people, calcium deposits and scarring develop that deform or even fuse the valve leaflets so that they do not close tightly. Another frequent cause, particularly in people diag- nosed before the age of 50, is a congenital (from birth) defect in a valve, for example, the bicuspid valve, which may calcify it. Very high levels of LDL (low density lipoprotein) cholesterol also promote increased calci?cation (forming of calcium deposits) around the heart valve. Aortic stenosis is more common in men.
If the stenosis is severe, replacement of the valve (see page 206) may be required. After surgery, most people are able to resume a normal lifestyle. Balloon valvuloplasty (inserting a balloon-tipped catheter; see page 204) of the aortic artery is a temporary solu-
tion in adults if they are not able to have surgery when the stenosis is diagnosed. In some young adults or children, valvuloplasty will open the valve.