Aortic stenosis (AS)

• What is Aortic Stenosis (AS)?
• Statistics
• Risk Factors
• Progression
• Symptoms
• Clinical Examination
• How is it Diagnosed
• Prognosis
• Treatment
• References

What is Aortic Stenosis (AS)?

Aortic stenosis (AS) is the constriction of the aortic valve of the heart – the valve that regulates the blood being pumped out by the heart and stops it from flowing back into the left ventricle of heart.

Statistics

About 4 in 1,000 people have a congenital valvular disease (most commonly a valve with two cusps) which may lead to the development of AS by a younger age – e.g. around 30 years of age. Approximately 40% of patients with the condition rheumatic heart disease will have aortic valve involvement. In addition, many elderly people (> 65 years of age) can have degenerative AS caused by atherosclerosis and calcification of the aortic valve, although only some will have symptoms.

Risk Factors

The most common predisposing factors are:

• Congenitally unicuspid or bicuspid aortic valve;
• Rheumatic heart disease;
• Old age.

It should be noted that a clinically similar picture can be produced by obstruction to left ventricular outflow at either above or below the valve.

Progression

With obstruction to the outflow of blood from the left ventricle there is an increase in the heart muscle. This in turn leads to increased demand for blood and oxygen from the heart and possibly leads to subsequent angina. Arrhythmias such as atrial fibrillation are often precipitated by the changes to the ventricle. The end result is left ventricular failure. Symptoms of failure usually begin to occur when the valvular orifice size is reduced to less than 1/3 of normal.

Symptoms

People with aortic stenosis may have a past history of rheumatic fever and have symptoms of atrial fibrillation – palpitations. Early in the disease, they may experience:

• Exercise-induced fainting;
• Angina; and
• Dyspnoea (shortness of breath).

Later in the disease, these progress to frank heart failure with dyspnoea, orthopnoea (shortness of breath while lying flat), and paroxysmal nocturnal dyspnoea (waking up gasping for breath).

Occasionally, they may present with myocardial infarction (heart attack).

How is it Diagnosed

The usual initial tests performed are:

1. ECG: may detect ventricular hypertrophy and ischaemia. Also associated myocardial infarction and atrial fibrillation.
2. Chest X-ray: May show a dilated aorta. Calcification of the aortic valve may be seen. In late disease, pulmonary oedema (“fluid on the lung”) may be seen.

Prognosis

The prognosis of untreated AS once symptoms have begun is poor, with the average life expectancy of a few years. However surgical treatments can usually halt the natural history of the disease before end stage heart failure has set in.

Treatment

General:

1. Avoidance of strenous activity as this increases demand on the heart.
2. Treating angina with beta blockers such as vasodilators may aggravate syncope.
3. Antibiotic prophylaxis against infective endocarditis.

Surgical replacement of the valve is indicated in all severe disease. Balloon valvotomies have been used in the past but the results are not as good, so this procedure is generally only used in patients waiting for surgery.

References

1. Schlant RC, Alexander RW, Fuster V (eds). Hurst’s The Heart (8th edition). New York, NY: McGraw-Hill; 1994. Book
2. Kumar P, Clark M (eds). Clinical Medicine (4th edition). Edinburgh: WB Saunders Company; 1998. Book