The heart is a beating muscle that pumps blood throughout the body. Inside the heart, four valves direct blood flow. Two valves control the flow of blood from the upper chambers, or atria, to the lower chambers, or ventricles. Two other valves control blood flow from the ventricles to the lungs and to the rest of the body. During a normal heartbeat, the left ventricle pumps oxygen-rich blood through the aortic valve to be distributed throughout the body. A healthy aortic valve has 3 cusps that open widely to allow blood flow during ventricular contraction; the cusps then close tightly to prevent backflow during ventricular relaxation. Aortic stenosis is a condition whereby the aortic valve becomes narrow, stiff, or thickened. This severely blocks the flow of blood coming from the ventricle. Aortic regurgitation is a condition that arises when the aortic valve weakens and does not close completely, causing blood to flow back into the left ventricle. With both conditions the heart must work harder to push the same amount of oxygen-rich blood to the rest of the body. This may lead to heart failure. When the valves do not work properly, they must be repaired or replaced. If the valve will be replaced, either an artificial (mechanical) valve or biological tissue valve can be used. Mechanical valves are very durable and last longer than biological valves. However, patients with mechanical valves will need to be on blood thinning medication for the rest of their lives to prevent blood clots. Minimally-invasive surgery is an option in some patients. The doctor may choose to access the heart through the ribs or a smaller incision in the upper chest. It reduces tissue damage and recovery time. During traditional artificial valve replacement surgery, an incision is made in the chest to access the heart. The heart is stopped and a heart-lung bypass machine takes over the work of the heart and lungs. Next, an incision is made in the lower aorta to locate the aortic valve. The damaged aortic valve is removed and replaced with the artificial valve. Once the heartbeat is restored, the valve is tested to make sure it is working properly. There are several potential complications associated with this procedure that should be discussed with a doctor prior to surgery. Surgery is often done to replace aortic or mitral valves, but your doctor can replace any heart valve. It is recommended to consult your doctor so they can determine the form of treatment most appropriate for you.