The aortic valve controls the direction of blood flow from the left ventricle to the aorta. When in good working order, the aortic valve does not impede the flow of blood between these two spaces. Under some circumstances, the aortic valve becomes narrower than normal, impeding the flow of blood. This is known as aortic valve stenosis, or aortic stenosis, often abbreviated as AS.

Pathophysiology

When the aortic valve becomes stenotic, it causes a pressure gradient between the left ventricle (LV) and the aorta. The more constricted the valve, the higher the gradient between the LV and the aorta. For instance, with a mild AS, the gradient may be 20 mmHg. This means that, at peak systole, while the LV may generate a pressure of 140 mmHg, the pressure that is transmitted to the aorta will only be 120 mmHg. So, while a blood pressure cuff may measure a normal systolic blood pressure, the actual pressure generated by the LV would be considerably higher.

In individuals with AS, the left ventricle (LV) has to generate an increased pressure in order to overcome the increased afterload caused by the stenotic aortic valve and eject blood out of the LV. The more severe the aortic stenosis, the higher the gradient is between the left ventricular systolic pressures and the aortic systolic pressures. Due to the increased pressures generated by the left ventricle, the myocardium (muscle) of the LV undergoes hypertrophy (increase in muscle mass). This is seen as thickening of the walls of the LV. The type of hypertrophy most commonly seen in AS is concentric hypertrophy, meaning that all the walls of the LV are (approximately) equally thickened.

Etiology

Causes of aortic stenosis include acute rheumatic fever, bicuspid aortic valve and congenital anomalies. As individuals age, calcification of the aortic valves may occur and result in stenosis.

Physical examination

It is most often diagnosed when it is asymptomatic. It is found on routine examination of the heart. A fairly loud systolic, crescendo-decrescendo murmur is heard loudest at the upper right sternal border, and radiates to the carotid arteries. The murmur increases with squatting, decreases with standing and isometric muscular contraction, which helps distinguish it from hypertrophic obstructive cardiomyopathy (HOCM). Respiration has no effect on the loudness of the murmur. The more severe the degree of the stenosis, the later the peak occurs in the crescendo-decrescendo of the murmur. Due to increases in left ventricular pressure from the stenotic aortic valve, over time the ventricle may hypertrophy, resulting in a diastolic dysfunction. As a result, one may hear a 4th heart sound due to the stiff ventricle. With continued increases in ventricular pressure, dilatation of the ventricle will occur, and a 3rd heart sound may be manifest.

Definition

When aortic valve stenosis occurs, the aortic valve, located between the aorta and left ventricle of the heart, is narrower than normal size.

Description

A normal aortic valve, when open, allows the free flow of blood from the left ventricle to the aorta. When the valve narrows, as it does with stenosis, blood flow is impeded. Because it is more difficult for blood to flow through the valve, there is increased strain on the heart. This can cause the left ventricle to enlarge and malfunction, resulting in reduced blood supply to the heart muscle and body, as well as fluid build up in the lungs.

Cause & symptoms

Aortic valve stenosis can occur because of a birth defect in the formation of the valve. Calcium deposits may form on the valve with aging, causing the valve to become stiff and narrow. Stenosis can also occur as a result of rheumatic fever. Mild aortic stenosis may produce no symptoms at all. The most common symptoms, depending on the severity of the disease, are chest pain, blackouts, and difficulty breathing.

Diagnosis

Using a stethoscope, a physician may hear a murmur and other abnormal heart sounds. An ECG, also called an electrocardiogram, records the electrical activity of the heart. This technique and chest x ray can show evidence that the left ventricle is enlarged. An x ray can also reveal calcium deposits on the valve, as well as congestion in the lungs. Echocardiography can pick up thickening of the valve, heart size, and whether or not the valve is working properly. This is a procedure in which high frequency sound waves harmlessly bounce off organs in the body. Cardiac catheterization, in which a contrast dye is injected in an artery using a catheter, is the key tool to confirm stenosis and gauge its severity.

Treatment

Treatment depends on the symptoms and how the heart's function is affected. The valve can be opened without surgery by using a balloon catheter, but this is often a temporary solution. The procedure involves inserting a deflated balloon at the end of a catheter through the arteries to the valve. Inflating the balloon should widen the valve. In severe stenosis, heart valve replacement is recommended, most often involving open-heart surgery. The valve can be replaced with a mechanical valve, a valve from a pig, or by moving the patient's other heart valve (pulmonary) into the position of the aortic valve and then replacing the pulmonary valve with an mechanical one. Anyone with aortic stenosis needs to take antibiotics (amoxicillin, erythromycin, or clindamycin) before dental and some other surgical procedures, to prevent a heart valve infection.

Prognosis

The prognosis for aortic valve stenosis depends on the severity of the disease. With surgical repair, the disease is curable. Patients suffering mild stenosis can usually lead a normal life; a minority of the patients progress to severe disease. Anyone with moderate stenosis should avoid vigorous physical activity. Most of these patients end up suffering some kind of coronary heart disease over a 10 year period. Because it is a progressive disease, moderate and severe stenosis will be treated ultimately with surgery. Severe disease, if left untreated, leads to death within 2 to 4 years once the symptoms start.

Prevention

There is no way to prevent aortic stenosis.

Key Terms

Aorta: The largest artery in the body, which moves blood from the left ventricle to the rest of the body.
ECG: Also called an electrocardiogram, it records the electrical activity of the heart.
Echocardiogram: A procedure in which high frequency sound waves harmlessly bounce off organs in the body providing an image so one can determine their structure and function.
Cardiac catheterization: A procedure in which dye is injected through a tube or catheter into an artery to more easily observe valves or blood vessels seen on an x ray.
Left ventricle: One of the lower chambers of the heart, which pumps blood to the aorta.
Murmur: An abnormal heart sound that can reflect a valve dysfunction.
Rheumatic fever: A bacterial infection that often causes heart inflammation.
Pulmonary valve: The valve located between the pulmonary artery and the right ventricle, which brings blood to the lungs.

For Your Information

Books

Bender, Jeffrey R. "Heart Valve Disease." In Yale University School of Medicine Heart Book, edited by Barry L. Zaret, et al. New York: Hearst Books, 1992, 167-175.
Braunwald, E. "Aortic Stenosis." In Heart Disease: A Textbook of Cardiovascular Medicine. Philadelphia: W.B. Saunders Company, 1997, 1035-1045.
McGoon, Michael D. "Aortic Stenosis." In Mayo Clinic Heart Book. New York: William Morrow and Company, 1993, 65-66.
Other
Loyola University Medical Center. "Aortic Stenosis," by Aly Rahimtoola. http://www.meddean.luc.edu/develop/arahimtoola/intro.htm.
Ochsner Heart and Vascular Institute. "Aortic Stenosis." http://www.ochsner.org/pedcard/as.htm.

Gale Encyclopedia of Medicine. Gale Research, 1999.

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