The heart pumps blood to the body through the aorta, a large blood vessel leading from the left lower chamber (the left ventricle). The aortic valve is the valve that guards the opening of this great vessel, and has three cusps of leaflets. Its function is to prevent blood pumped out into the aorta from leaking back into the left ventricle when the heart relaxes in between beats. Aortic stenosis (AS) is the condition in which the aortic valve in the heart is abnormally narrowed.
As a result, the heart cannot pump blood efficiently to the body and must work harder. This puts strain on the heart which causes the signs and symptoms of AS. This condition needs to be treated once symptoms appear as the mortality rate is high, mostly due to sudden death. It is the third most common cardiovascular condition in the developed world.
Symptoms of Aortic Stenosis (AS)
The degree of AS determines the symptoms. While mild AS is usually asymptomatic, severe narrowing leads to the manifestation of symptoms such as:
- Chest pain or a feeling of tightness when one is engaged in physical activity
- Faintness or dizzy spells during physical activity
- Fatigue during physical activity
- Shortness of breath especially during physical activity
- Palpitations with physical activity
- In children, failure to thrive and loss of appetite
- Swelling of the ankles and feet
Some of these symptoms point to the presence of heart failure which requires emergency medical treatment.
AS occurs in many situations:
- Congenital heart defect: the most common congenital heart disease is bicuspid aortic valve, or an aortic valve in which there is only two leaflets instead of three. This often fails to function as well as the normal valve, especially as time goes on.
- Calcification of the valve: with age the heart valves tend to acquire calcium deposits over sites of repeated trauma. This may lead to increased rigidity and thickening of the aortic valve, with narrowing of the orifice especially if the valve is already abnormal. This is usually suspected when AS occurs at a younger age than usual. AS due to calcification without any valve abnormality typically affects people who are above 70 or 80 years of age.
- Rheumatic fever: This autoimmune disease eats away at the heart valves and causes scarring, calcification, fibrosis and damage to the structure and function of the valves. All these can result in AS later.
- Other factors such as chronic kidney disease, diabetes, hypertension, dyslipidemia and a history of chest region irradiation may also increase the risk of AS.
AS may lead to a variety of complications such as:
- Heart failure due to overstrain on the left ventricle
- Blood clots
- Arrhythmias or irregular heartbeat
- Infective endocarditis
- Strokes and bleeding
- Sudden death
AS may be suspected from the symptoms in the presence of a characteristic heart murmur on auscultation of the chest. While a chest X-ray and ECG may add to the weight of the suspicion, the gold standard for diagnosis is echocardiography. This test helps evaluate the structure of and blood flow through the cardiac chambers and valves as well as the heart pumping action.
Sometimes exercise testing is advised to help manifest the symptoms of AS which are typically absent at rest. Other tests include CT, MRI, and cardiac catheterization, depending on the ease with which the diagnosis is reached.
The management of AS is simple when the patient is asymptomatic and consists primarily of limiting strenuous exertion and regular monitoring. Lifestyle factors should be attended to and factors which worsen the condition should be treated, such as hypertension or diabetes.
In the presence of severe symptoms, surgical treatment is recommended. Aortic valve repair is rarely performed, but valve replacement, transcatheter aortic valve replacement (TAVR), or balloon valvuloplasty, may be carried out. In the latter a specialized balloon is guided into the valve opening and inflated to stretch the orifice before removal. It is more palliative than curative as the AS tends to recur later. Valve replacement may be done using mechanical or biological valves, the latter having a shorter lifetime and needing to be replaced after a varying number of years. Mechanical valves tend to cause clot formation and thus these patients must take blood thinners for life. TAVR is considered in people who may be at higher risk for complications from open surgery.
Women with AS should always discuss any medications they take with their physicians when they plan to conceive and whether they can safely undergo pregnancy, labor and delivery in their health condition. Some women may have surgery before becoming pregnant. Close monitoring of the pregnancy is always required, and in some cases the woman may be advised to avoid pregnancy because of a very high risk of serious complications.