Aortic valve replacement is heart surgery performed to replace a malfunctioning aortic valve, due to narrowing (stenosis) or leakage (regurgitation). The aortic valve can malfunction because of a congenital abnormality (abnormal from birth) or an acquired disease (diseased with age).
One of the most common congenital heart defects affecting babies is a bicuspid aortic valve, where the aortic valve does not develop normally while the baby is in the womb. A normal aortic valve has three leaflets, whereas a bicuspid aortic valve has only two leaflets. Patients with a bicuspid aortic valve may develop a narrowing or leakage of the aortic valve.
Two types of prosthetic (artificial) valves are available to replace the malfunctioning aortic valve:
- Mechanical Valves - Mechanical valves are created from man-made materials and are very durable. Because there is a tendency for blood to clot on mechanical valves, patients with artificial valves must take anticoagulants (sometimes called "blood thinners") for the rest of their lives. This medication prevents blood clots from forming on or around the valve.
- Biological Valves - Biological (tissue) valves are taken from pig, cow, or human donors. Xenograft valves are made from animal tissues, while homograft or allograft valves are retrieved from human cadavers. Pulmonary autograft valves are moved from the patient's pulmonary artery on the right side of the heart to the aortic position on the left. Biological valves don't last as long as mechanical valves, but the use of an anticoagulant often isn't needed.
Why is Aortic Valve Surgery necessary?
The aortic valve is the outflow valve of the left side of the heart, meaning that it opens during systole (when the ventricle contracts or squeezes blood out into the aorta and the rest of the body). When the aortic valve is too narrow or stenotic, the ventricle has to work harder to pump the blood out to the body. This extra work consumes significant energy and ultimately requires extra blood flow to the heart itself. If there is not enough blood flow, the heart becomes ischemic causing anginal chest pain. Aortic stenosis is often progressive, growing worse with time. As the valve gets tighter, the heart has to continue to work harder and harder to keep pumping blood out of the heart. At some point the heart can no longer compensate, resulting in episodes of low blood pressure or hypotension or even syncope. As the heart fails to compensate, fluid will build up in the lungs creating congestion.
When the aortic valve leaks, the heart has to work harder and similar problem occur. The ventricle must pump more blood with each contraction to produce the same forward output, creating a condition called volume overload. The heart can compensate for this volume overload for many months or years provided the leakage develops slowly. Eventually, the heart begins to fail producing shortness of breath and fatigue.