The aortic valve is one of four valves that control blood flow in the heart. The aortic valve specifically controls the blood that runs from the heart through your aorta and to the rest of the body. Over time or because of a congenital heart defect, you can develop aortic stenosis—a type of heart valve disease—which is narrowing of the aortic valve. This narrowing blocks the flow of blood to your body and forces your heart to work harder. You may need TAVR to replace a diseased aortic valve or to repair a replacement aortic valve that no longer works. Your doctor may recommend TAVR if you have a medical condition that makes it too risky to replace the valve during open-heart surgery, which is more invasive.

Cardiologists, or doctors who specialize in the heart, typically perform TAVR in a hospital. Before TAVR, your medical team will measure the valve opening, then give you medicines that relax you or put you to sleep, as well as medicines that prevent abnormal blood clots. During the procedure, your doctor will guide a thin, flexible tube called a catheter to your heart through vessels that can be accessed from the groin or thigh, abdomen, chest, neck, or collar bone. Inside the catheter is a folded replacement valve, which your doctor will implant securely within the old valve. Once your doctor is sure the new valve has been placed correctly, he or she will check for leaks and possible complications, such as a problem in the heart’s electrical signaling.

After a TAVR procedure, your hospital stay may be shorter and you may be able to return to daily activities, such as exercising and driving, sooner than with open-heart surgery. However, TAVR carries some risks, including stroke, damage and bleeding where the catheters were inserted; need for permanent pacemaker due to damage to the heart’s electrical signaling during the procedure; and injury to the kidneys or the heart. Sometimes the new valve leaks because it does not fit well. Your doctor may give you medicine to prevent infection or abnormal Blood clot. About a month after the procedure, your doctor will test to check how well the valve is working and how well you are healing. You may need follow-up visits every year to make sure the valve continues working as it should.

Heart Valve Structure and Function

A transverse section through the heart slightly above the level of the atrioventricular septum reveals all four heart valves along the same plane (Figure 19.12). The valves ensure unidirectional blood flow through the heart. Between the right atrium and the right ventricle is the right atrioventricular valve, or tricuspid valve. It typically consists of three flaps, or leaflets, made of endocardium reinforced with additional connective tissue. The flaps are connected by chordae tendineae to the papillary muscles, which control the opening and closing of the valves.

Figure 19.12 Heart Valves With the atria and major vessels removed, all four valves are clearly visible, although it is difficult to distinguish the three separate cusps of the tricuspid valve.

Emerging from the right ventricle at the base of the pulmonary trunk is the pulmonary semilunar valve, or the pulmonary valve; it is also known as the pulmonic valve or the right semilunar valve. The pulmonary valve is comprised of three small flaps of endothelium reinforced with connective tissue. When the ventricle relaxes, the pressure differential causes blood to flow back into the ventricle from the pulmonary trunk. This flow of blood fills the pocket-like flaps of the pulmonary valve, causing the valve to close and producing an audible sound. Unlike the atrioventricular valves, there are no papillary muscles or chordae tendineae associated with the pulmonary valve.

Located at the opening between the left atrium and left ventricle is the mitral valve, also called the bicuspid valve or the left atrioventricular valve. Structurally, this valve consists of two cusps, compared to the three cusps of the tricuspid valve. In a clinical setting, the valve is referred to as the mitral valve, rather than the bicuspid valve. The two cusps of the mitral valve are attached by chordae tendineae to two papillary muscles that project from the wall of the ventricle.

At the base of the aorta is the aortic semilunar valve, or the aortic valve, which prevents backflow from the aorta. It normally is composed of three flaps. When the ventricle relaxes and blood attempts to flow back into the ventricle from the aorta, blood will fill the cusps of the valve, causing it to close and producing an audible sound.

In Figure 19.13a, the two atrioventricular valves are open and the two semilunar valves are closed. This occurs when both atria and ventricles are relaxed and when the atria contract to pump blood into the ventricles. Figure 19.13b shows a frontal view. Although only the left side of the heart is illustrated, the process is virtually identical on the right.

Figure 19.13 Blood Flow from the Left Atrium to the Left Ventricle (a) A transverse section through the heart illustrates the four heart valves. The two atrioventricular valves are open; the two semilunar valves are closed. The atria and vessels have been removed. (b) A frontal section through the heart illustrates blood flow through the mitral valve. When the mitral valve is open, it allows blood to move from the left atrium to the left ventricle. The aortic semilunar valve is closed to prevent backflow of blood from the aorta to the left ventricle.

Figure 19.14a shows the atrioventricular valves closed while the two semilunar valves are open. This occurs when the ventricles contract to eject blood into the pulmonary trunk and aorta. Closure of the two atrioventricular valves prevents blood from being forced back into the atria. This stage can be seen from a frontal view in Figure 19.14b.

Figure 19.14 Blood Flow from the Left Ventricle into the Great Vessels (a) A transverse section through the heart illustrates the four heart valves during ventricular contraction. The two atrioventricular valves are closed, but the two semilunar valves are open. The atria and vessels have been removed. (b) A frontal view shows the closed mitral (bicuspid) valve that prevents backflow of blood into the left atrium. The aortic semilunar valve is open to allow blood to be ejected into the aorta.

When the ventricles begin to contract, pressure within the ventricles rises and blood flows toward the area of lowest pressure, which is initially in the atria. This backflow causes the cusps of the tricuspid and mitral (bicuspid) valves to close. These valves are tied down to the papillary muscles by chordae tendineae. During the relaxation phase of the cardiac cycle, the papillary muscles are also relaxed and the tension on the chordae tendineae is slight (see Figure 19.13b). However, as the myocardium of the ventricle contracts, so do the papillary muscles. This creates tension on the chordae tendineae (see Figure 19.14b), helping to hold the cusps of the atrioventricular valves in place and preventing them from being blown back into the atria.

The aortic and pulmonary semilunar valves lack the chordae tendineae and papillary muscles associated with the atrioventricular valves. Instead, they consist of pocket-like folds of endocardium reinforced with additional connective tissue. When the ventricles relax and the change in pressure forces the blood toward the ventricles, the blood presses against these cusps and seals the openings.

There are several ways your doctor can perform TAVR, depending on your health and the condition of your blood vessels. Your doctor usually guides a tube with the replacement valve through a blood vessel in your groin or thigh, called the femoral artery.

If your femoral artery is too small or damaged by disease, your doctor may guide the tube through vessels that can be accessed from the chest. This approach is called transapical access. Your doctor may cut into your chest through your breastbone or ribs to access the heart directly through the aorta or through the pointed end of the heart, called the apex.

Less commonly, your doctor may guide the tube through vessels accessed from the abdomen, neck, or collar bone.

• Abdomen. NHLBI researchers developed this approach, called transcaval access, to make TAVR available to high-risk patients whose leg arteries are too small or diseased for the standard approach. The doctor makes holes in both the vena cava, a major veins in your abdomen, and the nearby aorta. The doctor guides the tube with the replacement valve first through the vein and then through the aorta to the heart. You may be able to stay awake when the medical team does this procedure. This type of TAVR approach may benefit women, whose blood vessels are usually smaller than men’s are.
• Collar bone. Accessing the heart from the vessel under the clavicle, or collar bone, may be an option if you have had heart surgery before or if you have another condition that makes it more difficult to access other parts of the chest.
• Neck. With transcarotid access, your doctor will cut into one side of your neck to expose the carotid artery and closely monitor you while opening a hole in the artery for the tube. This type of procedure is rare but may be used when other options will not work.
• Septum. In rare cases, your doctor will reach the faulty valve by guiding the tube through a blood vessel from your thigh to the heart and poking a hole through the septum, the wall of tissue that separates the right and left atria of the heart.

Your doctor may also use additional techniques to help prevent complications. New approaches to doing TAVR are making the procedure available to more patients.

In some patients, a replacement valve can push aside an old valve flap, blocking blood flow to the heart. The result—coronary artery obstruction—is a rare but life-threatening complication of TAVR, and NHLBI researchers have invented a technique to prevent it. Called Bioprosthetic Aortic Scallop Intentional Laceration to prevent Iatrogenic Coronary Artery obstruction (BASILICA), the procedure involves using an electrified wire inside a catheter to cut the existing valve flap before placing the new valve. Without this technique, replacing a faulty valve would be too risky for these patients. Learn more about NHLBI's TAVR research.