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

There are four chambers in the heart and four heart valves to control blood flow between them.

• The tricuspid valve controls blood flow from the right atrium into the right ventricle.
• The pulmonary valve controls blood flow out of the right ventricle into the pulmonary artery (into the lungs).
• The mitral valve controls blood flow from the left atrium into the left ventricle.
• The aortic valve controls blood flow out of the left ventricle into the aorta (the major blood vessel leaving the heart).

If a heart valve isn’t working properly, two main problems can occur:

• valves don’t shut properly, causing regurgitation (leakage) 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 restricted

If the problem is mild, it may go unnoticed.  However, it can put excessive strain on the heart, making it less effective as a pump and more likely to have an abnormal rhythm.  It can also result in a back-up of pressure, causing fluid to accumulate in the lungs (pulmonary oedema) and lower leg (peripheral oedema).

Defective heart valves are also more vulnerable to infections from bacteria entering the bloodstream.

Treatment

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