Aortic Stenosis

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Overview

Aortic stenosis (AS), also called aortic valve stenosis, is a condition in which the aortic valve has become narrowed or constricted (stenotic) and does not open normally. Calcium in the blood can build up on the valve, causing a hardening (calcification) of the valve.

The aortic valve is located between the left ventricle, or lower chamber of the heart, and the largest artery (aorta). The left ventricle pumps oxygen-rich blood into the aorta, which carries it to the brain and the rest of the body.

When the aortic valve becomes stenotic, the ability of the left ventricle to pump blood out of the heart to the aorta and other arteries is impaired. The organs receive an insufficient supply of oxygen-rich blood, and blood may "back up" into the lungs, causing shortness of breath.

Anatomy

The aortic valve has three parts, called "leaflets," that open and close. It functions as a one-way valve: when the left ventricle contracts, the valve only allows blood to flow out of the left ventricle and into the aorta. When the heart relaxes between contractions, the aortic valve closes, preventing blood in the aorta from returning to the left ventricle.

If calcium deposits build up on the aortic valve, the valve becomes hardened (calcified) over time. When this occurs, the leaflets do not open normally and the volume of blood ejected from the left ventricle is reduced. The heart's ability to supply the body with blood decreases, and blood backs up into the lungs.

The left ventricle initially compensates for increased resistance caused by aortic stenosis by thickening (i.e., increasing muscle mass) to help eject blood through the stenotic aortic valve into the aorta.

This helps overcome aortic stenosis at first, but the left ventricle progressively increases in diameter (dilates), stiffens, and gradually loses its ability to generate enough contractile force to compensate for the stenotic aortic valve. If aortic stenosis remains untreated, the left ventricle becomes further dilated and less able to contract and expel blood into the aorta.

Incidence and Prevalence
Aortic stenosis affects approximately 5 out of every 10,000 people in the United States. It is more likely to affect men than women; 80% of adults with symptomatic AS are male.

Cause and Risk Factors

The most common cause of aortic stenosis is age-associated degeneration and calcification of the aortic valve, which often causes symptoms in elderly patients.

In the past, this type of degeneration of the valve was most common in patients who had rheumatic fever during childhood. Currently, rheumatic fever is rarely a cause of aortic valve degeneration.

About 1–2% of the population is born with only two valve leaflets and, for reasons not yet well understood, is at increased risk for developing aortic stenosis. These patients often develop symptoms between the ages of 40 and 60.

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