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Aortic Stenosis

By Guy P. Armstrong, MD

Aortic stenosis is a narrowing of the aortic valve opening that blocks (obstructs) blood flow from the left ventricle to the aorta.

  • The most common cause in people younger than 70 is a birth defect that affects the valve.

  • In people over 70, the most common cause is thickening of the valve cusps (aortic sclerosis).

  • People may have chest tightness, feel short of breath, or faint.

  • Doctors usually base the diagnosis on a characteristic heart murmur heard through a stethoscope and on results of echocardiography.

  • People see their doctors regularly so their condition can be monitored, and people with symptoms may undergo replacement of the valve.

The aortic valve is in the opening between the left ventricle and the aorta. The aortic valve opens as the left ventricle contracts to pump blood into the aorta (see Overview of Heart Valve Disorders). If a disorder causes the valve flaps to become thick and stiff, the valve opening is narrowed (stenosis). Sometimes the stiffened valve also fails to close completely and aortic regurgitation develops.

In aortic stenosis, the muscular wall of the left ventricle usually becomes thicker as the ventricle works harder to pump blood through the narrowed valve opening into the aorta. The thickened heart muscle requires an increasing supply of blood from the coronary arteries, and sometimes, especially during exercise, the blood supply does not meet the needs of the heart muscle. The insufficient blood supply can cause chest tightness, fainting, and sometimes sudden death. The heart muscle may also begin to weaken, leading to heart failure. The abnormal aortic valve can rarely become infected by bacteria ( infective endocarditis).

Causes

In North America and Western Europe, aortic stenosis is mainly a disease of older people—the result of scarring and calcium accumulation (calcification) in the valve cusps. In such cases, aortic stenosis becomes evident after age 60 but does not usually cause symptoms until age 70 or 80.

Aortic stenosis may also result from rheumatic fever contracted in childhood. Rheumatic fever is the most common cause in the developing world.

In people under 70, the most common cause is a birth defect, such as a valve with only two cusps instead of the usual three or a valve with an abnormal funnel shape. The narrowed aortic valve opening may not be a problem during infancy, but problems occur as a person grows. The valve opening remains the same size, but the heart grows and enlarges further as it tries to pump increasing amounts of blood through the small valve opening. Over the years, the opening of a defective valve often becomes stiff and narrow because calcium accumulates.

Symptoms

People who develop aortic stenosis as a result of a birth defect may not develop symptoms until adulthood.

Chest tightness ( angina) may occur during exertion. The symptoms go away with several minutes of rest. People with heart failure develop fatigue and shortness of breath during exertion.

People who have severe aortic stenosis may faint during exertion because blood pressure may fall suddenly. Fainting usually occurs without any warning symptoms (such as dizziness or light-headedness).

Diagnosis

  • Physical examination

  • Echocardiography

Doctors usually base the diagnosis on a characteristic heart murmur heard through a stethoscope and on results of echocardiography. Echocardiography is the best procedure for assessing the severity of aortic stenosis (by measuring how small the valve opening is) and the function of the left ventricle.

For people who have aortic stenosis but do not have symptoms, doctors often do a stress test. People who experience angina, shortness of breath, or faintness during the stress test are at risk of complications and may need treatment.

If the stress test is abnormal or if the person develops symptoms, cardiac catheterization is usually necessary to determine whether the person also has coronary artery disease.

Treatment

  • Valve replacement

Adults who have aortic stenosis but no symptoms should see their doctor regularly and should avoid overly stressful exercise. Echocardiography is done periodically, at intervals determined by the severity of the stenosis, to monitor heart and valve function.

Before surgery, heart failure is treated with diuretics (see Table: Some Drugs Used to Treat Heart Failure). Treating angina is often difficult because nitroglycerin, which is used to treat angina in people who have coronary artery disease, can rarely cause dangerously low blood pressure and worsen the angina in people with aortic stenosis.

In people who have aortic stenosis that causes any symptoms (particularly shortness of breath on exertion, angina, or fainting), or if the left ventricle begins to fail, then the aortic valve is replaced. Surgical replacement of the abnormal valve is the best treatment for nearly everyone, and the prognosis after valve replacement is excellent.

Sometimes, in children and young adults who were born with a defective valve, the valve can be stretched open using a procedure called balloon valvotomy. In this procedure, a catheter with a balloon on the tip is threaded through a vein or artery into the heart (see Cardiac catheterization). Once across the valve, the balloon is inflated, separating the valve cusps.

Increasingly, frail older people who are at high risk for complications during surgery can have their valve replaced through a catheter threaded up the femoral artery in a procedure called transcatheter aortic valve replacement (TAVR). In some cases, where there is peripheral artery disease in the legs, this catheter-mounted valve can be inserted through a small incision in the left side of the chest (transapical approach) or even under the shoulder (axillary approach). TAVR results in better survival and quality of life than medical therapy or surgery for these people.

People with an artificial valve must take antibiotics before a surgical, dental, or medical procedure (see Table: Which Procedures Require Preventive Antibiotics*?) to reduce the risk of an infection on the valve (infective endocarditis).

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