Aortic valve disease
The aortic valve is one of the valves of the heart. It lies between the left ventricle and the aorta. During ventricular systole, pressure rises in the left ventricle. When the pressure in the left ventricle rises above the pressure in the aorta, the aortic valve opens, allowing blood to exit the left ventricle into the aorta. When ventricular systole ends, pressure in the left ventricle rapidly drops. When the pressure in the left ventricle decreases, the aortic pressure forces the aortic valve to close. The closure of the aortic valve contributes the A2 component of the second heart sound (S2).
An aortic valve may be abnormal at birth: although this valve normally has three cusps it sometimes has two. This does not cause problems until later in life when it may become narrowed and cause aortic stenosis. Another defect at birth can cause aortic regurgitation later. These defects may be found at birth but aortic stenosis or regurgitation may also be caused later by rheumatic fever. There are also several other causes of aortic regurgitation. It may occur with joint diseases such as rheumatoid arthritis, ankylosing spondylitis, and a rarer condition called Reiter's syndrome. It may also occur with the skin condition psoriasis and as a long-term complication of syphilis. This is now rare. Infection on an abnormal aortic valve leads to a disease called infective endocarditis. This usually produces or causes a worsening of any leaking of the valve.
The aortic valve controls the flow of oxygenated blood pumped out of the heart from the left ventricle into the aorta, the main artery leading to the rest of the body. If the valve is abnormally narrow (aortic stenosis), the heart must work harder for a sufficient amount of blood to be pumped with each beat. On the other hand, if the valve does not close properly, it may cause aortic regurgitation because some of the blood being pumped out into the aorta regurgitates, or leaks backward, into the left ventricle with each beat. In either case, the work of the ventricle increases. As a result, its muscular wall thickens (a condition known as hypertrophy) and the left ventricle may become larger (dilate). Aortic stenosis refers to the process of thickening and stiffening in the valve. The valve itself, however, may continue to function adequately for years, with nothing more than a heart murmur heard by the physician on examination with a stethoscope. The murmur is caused by turbulence of blood passing through the valve. In aortic stenosis, the aortic valve becomes narrowed and blocked by hard, calcified deposits, or in some people, from rheumatic fever years earlier. This condition is present in about 4 percent of all elderly people. Severe aortic valve stenosis can cause fainting (because of impaired blood flow to the brain across the narrowed valve); heart failure and shortness of breath (when the heart's muscle becomes unable to pump blood in a forward direction through narrow opening); and chest pain (because of increased work and a lack of sufficient oxygen reaching heart muscles). Aortic regurgitation is usually asymptomatic until middle age. Patients may present with heart failure or chest pain. Some causes of aortic regurgitation include congenitally bicuspid (only two cusps instead of three) valves, infective endocarditis, and high blood pressure.
An aortic valve disorder usually does not cause any symptoms in its early stages. As the problem progresses, it may produce shortness of breath, angina (chest pain), light-headedness, dizziness, and even fainting, especially upon exertion. Many elderly people with aortic stenosis remain free of symptoms. Most cases of aortic valve disease can be diagnosed by a physical examination, during which a characteristic heart murmur may be detected. A chest X-ray, an electrocardiogram (EKG, to determine whether the heart is enlarged), and an echocardiogram (ultrasound study of heart muscle and valves) also may be done. If enough physical symptoms are present, cardiac catheterization may be necessary to better evaluate the valve and heart function.
A mild valve abnormality needs no treatment. The symptoms of heart failure (breathlessness and ankle swelling) need medication called diuretics. These get rid of the excess fluid that the kidneys retain and you pass more urine. If this treatment is not enough or if the valve defect (particularly stenosis) poses any threat, valve replacement surgery must be considered. Regular check-ups are important to make sure that the valve defect and its effect on the heart's pumping does not become dangerous. If you get breathless, you should seek advice. Treatment may need to be started or increased. If you have aortic stenosis (narrowing), a blackout or dizziness may mean some deterioration has occurred. You should then see your doctor as soon as possible. If germs get into the bloodstream there is a risk of getting infection on an abnormal aortic valve. This is called infective endocarditis. Germs get into the blood through the gums after dental treatment or with other operations or investigations which use instruments passed inside the body. Prevention, by taking antibiotics, is better than cure. They are given, usually by mouth, an hour before dentistry or an operation. You should carry a card with all the details. Show it to any doctor or dentist treating you.
Aortic stenosis may eventually cause blackouts or even sudden death. Regular check-up is essential to ensure that it does not get worse. If the condition is severe it is extremely important to have a new valve inserted. For aortic regurgitation, regular checks are also important to make sure that the heart is not strained. This may happen even with mild symptoms. If valve surgery is left too late, it may then be too late to make any difference to your symptoms or outlook. |
