Heart valve disease Dr Trisha Macnair A heart murmur - a sound created by the flow of blood through the heart - can be perfectly normal, but it may be a sign of a problem with one of the heart's valves. If the problem is mild, it may go unnoticed.

In this article

What is heart valve disease? Symptoms

Causes and risk factors Treatment and recovery

Each heart valve is a set of flaps or cusps that open or close like gates to control the flow of blood through the heart and its chambers. The valves allow blood to flow in one direction only through the heart; if blood starts to flow back the other way, they're forced shut.

There are four chambers in the heart and four heart valves to control blood flow between them. If a heart valve isn't working properly, blood flow is thrown into chaos.

The two main problems that occur are:

• Valves that don't shut properly, causing regurgitation of blood back across the valve in the wrong direction (for example, from the aorta back into the heart)
• Valves that won't open properly, known as stenosis of the valve, which means blood flow through the valve is limited

Another heart valve problem, which used to be diagnosed frequently among otherwise healthy people, is a condition called mitral valve prolapse, or floppy valve syndrome.

It was thought that one of the cusps on the valve would flip back the wrong way making a characteristic clicking sound and a murmur. It's now thought that as many as two per cent of adults have this syndrome and some experts say it's just a variation of normal and not a disease at all.

If the problem is mild, it may go unnoticed. However, it can put excessive strain on the heart, making it swollen, less effective as a pump and more likely to have an abnormal rhythm. This is known as heart failure and it results in a backlog of pressure, causing fluid to accumulate in the lungs (pulmonary oedema) and lower leg (peripheral oedema).

Stenosis of the aortic valve (the commonest valve disease in the developed world) can interfere with the blood supply through the coronary arteries to the heart muscle, leading to chest pain known as angina. It can also cause fainting or blackouts, especially on exertion, as the heart is unable to push enough blood out through the narrowed aortic valve, to the brain, to meet increased demands. In 4% of the patients with aortic stenosis, the first symptom is sudden death, usually during strenuous exertion.

Valve disease can develop before birth (congenital) or during life as a result of many different conditions. For example, a heart attack can result in damage to the tiny muscles which control the valves, while heart failure (caused by high blood pressure, disease of the heart muscle and many other conditions) may cause the heart to dilate, interfering with valve function.

Other causes include rheumatic fever. This condition, caused by a bacterial infection, is very rare in the developed world these days as antibiotics are widely available. But it is sometimes seen in the elderly.

Endocarditis is another bacterial infection which can target the heart valves, especially when there are already some abnormalities of the valves - people with diseased heart valves should always take antibiotics when they have surgery or major dental work as they are more vulnerable to infections from bacteria entering the bloodstream.

Many people with mild heart valve problems live completely normal lives with no need for treatment. However, medication or surgery may be necessary.

Treatment of underlying conditions such as heart failure (or diseases causing heart failure such as high blood pressure, abnormal heart rhythms or an under- or over-active thyroid gland) can improve valve function.

Surgery ranges from minor procedures to open a stenosed valve (for example, by passing a tiny balloon through the blood vessels and inflating it once in place) to operations to replace a diseased valve with an artificial one.

Artificial valves may be mechanical (metal or plastic) or bioprosthetic (made from animal or human tissues). With mechanical valves, it's often necessary to take blood-thinning drugs long-term to prevent clots forming. However these valves tend to last longer than bioprosthetic valves.

You can find out more about surgery for heart valve disease and artificial valves from the US National Library of Medicine.

This article was last medically reviewed by Dr Trisha Macnair in February 2009.