Bicuspid Aortic Disease
Bicuspid aortic disease occurs when a defect is present in the valve that opens and shuts to allow blood flow from the heart through the aorta. While the defective valve may be easy to see, the defect also causes changes in the tissues of the aorta and the heart. Between one and two percent of all people have this defect, and it affects more men than women.
A normal aortic valve (see below) has three leaflets (also known as flaps or cusps). These open and close to control the flow of blood into the aorta from the left ventricle of the heart as it beats. When the flaps come together as the valve closes, the shape is like a circle divided into thirds.
In contrast, a bicuspid aortic valve has only two leaflets. (Refer to the left figure in the diagram.) It is sometimes described as looking like the mouth of a fish as it opens and closes.
Bicuspid aortic disease refers to any combination of the following:
- An aortic valve that has only two, instead of the normal three, flaps to open and shut the valve
- An aortic dilation, aneurysm or dissection (a tear in the wall of the aorta)
- Deterioration of the valve or the aorta
- Rapid changes in blood pressure with activity or stress (labile hypertension)
- Bicuspid aortic valve stenosis
While doctors and researchers know much about the aortic valve itself, how it affects the overall health of the aorta and the heart is still being studied. The aorta becomes enlarged more often in persons with a bicuspid aortic valve than in those with normal aortic valves.
The precise nature of the defect in the valve varies from one person to another. Often the condition is silent. In some cases it's possible to live a normal life span without the condition causing problems. The defect or resulting complications are frequently found during a routine physical exam or tests to diagnose another condition.
A defective aortic valve can lead to potentially life-threatening conditions, including the formation of bulging weak spots (aneurysms) or tears in the wall of the aorta (dissections). Depending on the nature of the defect, blood flowing through the valve may make an abnormal sound, called a murmur. While some bicuspid aortic valves are silent, a murmur may be the first sign of an abnormal aortic valve. A person with bicuspid aortic disease may also experience rapid changes in his or her blood pressure during activity or stress.
Causes and Risk Factors
This disease runs in families, although it may skip generations. Much research is currently being conducted to uncover any genetic aspects of this condition. Research shows that in families with this condition, some members may develop ascending aortic aneurysm, even when their aortic valve appears normal. Since predicting who may be affected is not possible, monitoring all family members is important, including parents, children, brothers and sisters, as well as extended family members, such as nephews, nieces and grandchildren.
No tests are currently available to learn who will experience failure of the valve, aortic aneurysm or aortic dissection. Treatment plans have been developed to assist people who may be at risk of complications from a defective aortic valve. Education, early and regular diagnostic monitoring, medical treatment and lifestyle modifications are key to successfully managing this condition.
The typical patient who seeks treatment for an aortic valve defect or related complications caused is a man in his 50s. The condition, however, does occur in both men and women of all ages. The younger a person is when the bicuspid aortic valve starts leaking, the greater his or her chances are of a tear in the walls of the aorta or an aneurysm forming or rupturing.
A doctor bases a diagnosis on the patient's medical and family history, symptoms and a physical examination. A number of tests may be ordered to track the progress of the disease or to confirm it, including:
- An echocardiogram
- A computed tomography scan
- A magnetic resonance imaging scan
- Nuclear medicine tests (e.g., adenosine and thallium) may be used to determine whether there is blockage of the coronary artery
- Ultrasound examination of the carotid arteries
- Chest X-rays
No matter how the valve is failing, it should be monitored. Eventually, surgery will be needed to prevent lasting damage to the heart.
This condition can lead to a number of complications, including:
- Leaking of blood back into the heart because the valve doesn't close tightly. Depending on how much leaking occurs, there may be strain on the heart. Because the heart has to pump the blood that flowed back into it, the muscles of the left ventricle (the lower left chamber of the heart) may bet stretched. Even with surgery, the heart may not recover its efficiency in pumping.
- An inability of the valve to open widely or the development of calcium deposits on the leaflets. As the valve opening becomes narrower (this is called a stenosis), the heart has to work harder to force the blood through the valve. This stress may make the heart muscle thicken (also known as an over-pressurized heart). The heart can't relax between beats and becomes very stiff and inefficient.
- The mitral valve may leak blood due to bicuspid leaflets.
- One of the three layers of the wall of the aorta becomes thin and weak. As a result, the aorta cannot stretch and contract properly when the heart beats and pumps blood into the aorta.
Treatment of bicuspid valve disease includes:
- Drugs to control blood pressure such as ACE inhibitors, ARBs, calcium channel blockers and beta blockers. This approach is designed to slow the enlargement of the aorta, reduce the risk of the aorta tearing or rupturing and to reduce the amount of blood flowing back into the heart through the valve. If heart failure is present, a diuretic and possibly digoxin may be added and beta blocker doses modified. In general, systolic blood pressure is managed to stay in a range of 105 to 110 during normal activity.
- Lifestyle changes including eating a healthy, low-fat diet that is high in protein and fiber, maintaining a healthy weight, exercising regularly and quitting smoking and avoiding second hand smoke. Exercise is helpful and strongly encouraged, including power walks of 15 to 30 minutes two to three times daily. However, heavy lifting is prohibited due to the pressure it exerts on the aorta.
- to provide a stable, long-term solution. Surgical approaches include replacing the diseased portion of the aorta with a Dacron graft or replacing the aortic valve with one that is either biological or mechanical. Usually the valve is replaced before it totally fails to avoid lasting damage to the heart.
Ongoing Care after Surgery
Medical care after surgery focuses on protecting the graft, the remaining aorta, the aortic valve and the cardiovascular system in general. Regular monitoring is done.
It is also important to prevent possible infection of the valves or heart. This includes taking antibiotics before having your teeth cleaned or having other types of dental procedures or before any invasive procedure. While the skin is a natural barrier to infection, any procedure that penetrates the skin increases the risk of infection. That includes procedures such as a breast biopsy, removal of an ingrown toenail or a wart on the hand, a simple hernia repair or an angiogram or heart catheterization.
A person who has or has had aortic valve disease should information all medical professionals of their condition. If any questions arise, the patient's cardiac care providers should be consulted. In some cases, oral antibiotics may not be sufficient, and intravenous antibiotic therapy may be required. Endocarditis is a severe infection that is difficult to treat and potentially life threatening. It is important that all possible steps are taken to prevent it.
In some cases (such as when a person receives a mechanical valve replacement or has an irregular heart beat for more than 72 hours after surgery) a patient may be given drugs to prevent their blood from clotting. Such drugs include coumadin. The level of anti-clotting drug in the blood is regularly monitored. This can now be done in the home with special devices. Aspirin may also be given.