The aortic valve lies between the left ventricle and the aorta. The aorta is the main artery that takes blood from the heart to the body. The aortic valve has three flaps (cusps). Blood flows through the valve when the left ventricle contracts at the early part of the heartbeat. When the left ventricle relaxes, the aortic valve closes. Then the mitral valve opens to allow more blood into the ventricle ready for the next heartbeat.
Aortic stenosis means that when the aortic valve opens, it does not open fully. It is narrowed (stenosed) when it is open. Therefore, there is a partial restriction of blood flow from the left ventricle into the aorta. Basically, the more narrowed the valve, the less blood that can get through, the more severe the problem is likely to be. In some cases, aortic stenosis occurs at the same time as aortic regurgitation.
Causes of aortic stenosis
Age-related calcification of the valve
This is a common cause. Deposits of calcium build up in the valve in some older people. It is not clear why this happens. This calcification makes the valve stiff and open less easily. It can be mild and cause little narrowing. However, in time it can become more severe. About 1 in 20 people aged over 65 have some degree of this type of aortic stenosis.
Other causes of aortic stenosis are uncommon and include:
- Some congenital heart problems. It is then usually part of a complex heart deformity.
- Infection of the valve (endocarditis).
- An abnormality of the tissues just above or just below the valve. This may cause a narrowing and restrict blood flow, and cause problems identical to stenosis of the valve.
Symptoms of aortic stenosis
- If the valve is only mildly narrowed there are likely to be no symptoms.
- If the narrowing becomes worse the left ventricle has to work harder to pump blood into the aorta. The wall of the ventricle becomes thickened (hypertrophied). Symptoms that may then develop include:
- Dizziness and faints (especially on exertion) due to the restricted blood supply.
- Chest pain (angina) on exertion. This occurs because of the increased need for oxygen by the thickened ventricle and because of reduced blood flow to the coronary arteries.
- Irregular heartbeat which may be felt as palpitations.
- If the narrowing is severe the left ventricle may not function properly and heart failure can develop. This causes shortness of breath, tiredness, and fluid build-up in various tissues of the body.
Complications of aortic stenosis
- Heart failure may become severe and life-threatening.
- Endocarditis is an uncommon complication. Unless promptly treated, endocarditis can cause serious illness.
How is aortic stenosis diagnosed?
- A doctor may hear a heart murmur or other abnormal noises when listening with a stethoscope. Murmurs and noises are due to blood passing through abnormal valves, or to abnormal movement of valves. Aortic stenosis causes typical murmurs and noises.
- A chest X-ray may show some calcification around the aortic valve.
- An electrocardiogram (ECG) can show that the left ventricle is thickened.
- An echocardiography can confirm the diagnosis. This is an ultrasound scan of the heart.
- Cardiac catheterisation is sometimes done to assess the severity of the stenosis.
Treatments for aortic stenosis
If the narrowing is mild and there are no symptoms then treatment may not be needed. However, surgery is usually advised in most cases when symptoms develop. This is because studies have shown that once symptoms develop, the average survival is two to three years if the valve remains stenosed (narrowed). With surgery, the outlook is very good.
An operation to fix aortic stenosis is a commonly done procedure. It has a very good chance of a success. The possible options include the following:
- Valve replacement. This also requires open heart surgery. The replacement may be with a mechanical or a tissue valve.
- Stretching the stenosed valve (balloon valvuloplasty). This is an option that is sometimes considered. This does not require open heart surgery. However, for adult patients, balloon valvuloplasty tends to be used only in those who are unsuitable for valve replacement surgery. This is because the improvement in the flow across the valve (following balloon valvuloplasty) does not usually last for very long. valve replacement surgery tends to give better long-term results.
Antibiotics to prevent endocarditis
People at risk of endocarditis need to take antibiotics if they actually have an infection at the time that dental or surgical procedures are undertaken.
Good oral and dental hygiene are also thought to be important in helping to prevent infective endocarditis.
What is the prognosis (outlook) for people with aortic stenosis?
Surgical treatment has greatly improved the outlook in most people who have more severe stenosis. Surgery to widen or to replace the valve has a very good success rate. The outlook is good if the valve is treated before the heart becomes badly damaged.