Section 3. Heart and Blood Vessel Disorders

Chapter 28. Heart Valve Disorders

Topics: Introduction | Mitral Regurgitation | Mitral Valve Prolapse | Mitral Stenosis | Aortic Regurgitation | Aortic Stenosis | Tricuspid Regurgitation | Tricuspid Stenosis | Pulmonary Stenosis

Aortic Stenosis

Aortic stenosis is a narrowing of the aortic valve opening that increases resistance to blood flow from the left ventricle to the aorta.

In aortic stenosis, the wall of the left ventricle usually thickens because the ventricle must work harder to pump the blood through the narrowed valve opening into the aorta. The thickened wall occupies space inside the ventricle and thus makes the interior of the left ventricle smaller. The thickened heart muscle requires an increasing supply of blood from the coronary arteries, and eventually, the blood supply becomes inadequate. The heart muscle can be damaged when it does not receive enough blood. A damaged heart cannot pump enough blood for the body's needs, leading to heart failure.

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 begins after age 60 but does not usually produce symptoms until age 70 or 80. Aortic stenosis may also result from rheumatic fever contracted in childhood. When rheumatic fever is the cause, aortic stenosis is usually accompanied by mitral stenosis, leakage (regurgitation), or both.

In younger people, 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 (see Section 23, Chapter 265). The narrowed aortic valve opening may not be a problem in infancy but becomes one 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 and Diagnosis

Chest pain (angina) occurs during exertion because the blood supply to the enlarged heart muscle is inadequate. Eventually, heart failure develops, causing fatigue and shortness of breath during exertion.

People who have severe aortic stenosis may faint during exertion because blood pressure may fall suddenly. This sudden fall in blood pressure occurs because the arteries in skeletal muscles dilate during exercise to receive more oxygen-rich blood, but the narrowed valve opening prevents the left ventricle from pumping enough blood to compensate. People who have severe aortic stenosis can die suddenly, so treatment should not be delayed.

The damaged aortic valve can become infected by bacteria, resulting in infective endocarditis.

Doctors usually base the diagnosis on a characteristic heart murmur heard through a stethoscope, on pulse abnormalities, and on results of electrocardiography indicating thickening of the heart wall. For people who experience angina, shortness of breath, or faintness, echocardiography (see Section 3, Chapter 21) is the best procedure for measuring the thickness of the left ventricle wall. Echocardiography is used to monitor how quickly the left ventricle wall is thickening. Color Doppler echocardiography shows different rates of blood flow through the narrowed valve opening in different colors and can indicate how narrow the valve opening is. Cardiac catheterization (see Section 3, Chapter 21) shows exactly how narrow the opening is and can show whether the coronary arteries are also narrowed because of coronary artery disease.

Treatment

Adults who have aortic stenosis but no symptoms should see their doctor regularly and should avoid overly stressful exercise. Echocardiography is performed periodically to monitor heart size and valve function. If heart size increases significantly or valve function worsens, the doctor may recommend surgery.

In adults who have aortic stenosis that causes fainting, angina, or shortness of breath during exertion, the aortic valve is surgically replaced, preferably before the left ventricle is irreversibly damaged. Echocardiography, usually performed periodically, can help doctors determine when to schedule surgery. Before surgery, heart failure (indicated by shortness of breath) is treated with diuretics (see Section 3, Chapter 25). Surgical replacement of the abnormal valve is the best treatment for adults of all ages, and the prognosis after valve replacement is excellent. People with an artificial valve must take antibiotics before a surgical, dental, or medical procedure (see Section 3, Chapter 29) to reduce the risk of an infection on the valve (infective endocarditis).

For children who have severe stenosis, surgery may be performed even before symptoms develop, because sudden death may occur before symptoms develop. Safe, effective alternatives to valve replacement are surgical repair of the valve and balloon valvuloplasty. In balloon valvuloplasty, a balloon-tipped catheter is threaded through a vein and eventually into the heart (see Section 3, Chapter 21). Once inside the valve, the balloon is inflated to expand the valve opening. However, later, when children are fully grown, the valve usually must be replaced. In adults, stenosis always recurs after balloon valvuloplasty; so among adults, this procedure is used only for frail older people who cannot tolerate surgery.