Aortic Valve Surgery

The aortic valve is a one-way valve that prevents backflow of blood from the aorta, which is the large artery coming out of the heart, back into the left ventricle, the main pumping chamber of the heart. This valve can develop two problems. It can become leaky (aortic regurgitation), or it can become blocked (aortic stenosis), or there can be a combination of the two conditions. The causes of the abnormalities can range from congenital defects to wear and tear caused by old age and calcium build-up to infections of the valve itself. If left untreated, aortic valve disease can lead to weakness of the heart muscle, heart failure, and, in extreme cases, death. With aortic stenosis, patients will usually complain of worsening shortness of breath with exertion, some have chest discomfort, and some develop fainting or near-fainting episodes. The symptoms associated with aortic regurgitation are similar, but may occur much later in the disease process, when the heart has already failed. Once the valve is sufficiently blocked or leaky, it may need to be replaced.

The patient is put to sleep in the operating room, and the cardiopulmonary bypass machine (heart-lung machine) is used to allow the heart to be opened so that the surgeon can expose and remove the patient's damaged heart valve. Once the old valve has been removed, a new valve is sewn into the position of the old valve. There are two general types of prosthetic valves that can be used to replace a person's own diseased aortic valve: mechanical or tissue. Each of these types of prosthetic replacement valves has advantages and disadvantages, and the heart surgeon should discuss these with the patient prior to surgery.

The mechanical replacement valve shown at left has the advantage that it lasts a longer time without structural problems when compared to the tissue valves. The main disadvantages have to do with a need for life-long blood thinner to prevent blood clot formation on the valve. This increases the chance of bleeding problems during the patient's lifetime. Although most bleeding episodes are minor, there can be major bleeding complications which may require blood transfusions or may even be life-threatening. Without adequate thinning of the blood, there is an increased risk of blood clots forming on the valve, with the potential for these clots to break free into the blood stream. These free clots (known as emboli) may travel to distant organs in the body. If a clot travels to the brain, a stroke may occur, or, if emboli travel to an arm or leg, the limb could become cold, pulseless, motionless, and extremely painful.

The valve shown at right is a tissue valve obtained from the heart valve of pigs or the pericardium (sac surrounding the heart) of cattle. The advantage of these types of valves is that there is normally only temporary or no need for blood thinner. The disadvantage is that these valves may have a decreased structural durability compared to mechanical valves, causing earlier valve lifespan. In certain patients the valves may become calcified and stiff and malfunction in just a few years. The likelihood of blood clot formation is not zero, but is much less than what is seen with mechanical valves.

A second type of tissue valve is one that comes from a human being. When a person dies, he or she may donate tissue for use in transplantation. The donated aortic valve can be used to replace a patient's diseased aortic valve. This is called a homograft. The advantages are that no blood thinner is usually required, that these valves can be used when a very small mechanical or animal valve is unsuitable for the patient, that there may be less risk of infection when used for the treatment of infected valves (endocarditis), and there may be improved durability and valve lifespan compared to other tissue valves. The disadvantages are that they are more expensive, they are scarce, and they are technically more difficult to insert.