The problem
In a healthy heart, the left atrium fills with oxygenated blood from the lungs and passes it to the left ventricle. It is the job of the left ventricle to pump the blood through the rest of the body. When the left ventricle contracts, it pushes the blood through the aorta. From the aorta, the blood branches off to the different parts of the body. The aortic valve connects the ventricle to the aorta.
Usually, the aortic valve has three leaflets that separate easily to allow the blood to pass. In AVS, various abnormalities can occur. There may be only two leaflets, which are then thicker and stiffer than normal, and do not separate easily. This common abnormality is caused a bicuspid aortic valve. The ventricle has to work harder to compensate, and enlarges, resulting in hypertrophic cardiomyopathy. In other cases, the obstruction is so severe that the ventricle cannot compensate, and heart failure results. This is rare, and occurs only in infants with severe cases of AVS. AVS is not likely to lead to heart failure in older children.
