Coronary heart disease: a non-communicable disease: In some people heart valves may become faulty, preventing the valve from opening fully, or the heart valve might develop a leak. Students should understand the consequences of faulty valves. Faulty heart valves can be replaced using biological or mechanical valves.

The idea

Heart valves keep blood flowing one way through the heart. A valve that cannot open fully is stiff or narrowed, so blood cannot pass easily and the heart must work harder to push blood through. A leaky valve does not close tightly, so blood flows backwards instead of moving on. Both faults reduce the efficiency of the heart's pumping, which can cause breathlessness, tiredness and fluid build-up. Faulty valves can be replaced with biological valves, taken from an animal or a human donor, or mechanical valves made from materials such as metal or polymer. Biological valves may wear out sooner, while mechanical valves are durable but usually require long-term medication to reduce clotting.

What earns the marks

• States that valves normally keep blood flowing in one direction through the heart.
• Describes a valve that cannot open fully as stiff or narrowed, so blood flow through it is restricted.
• Describes a leaky valve as one that does not close tightly, allowing blood to flow backwards.
• Explains that both faults make the heart work harder and reduce the efficiency of blood circulation.
• Names biological and mechanical replacement valves and gives a relevant difference between them.
• Links valve replacement to restoring one-way blood flow and improving symptoms.

Common mistakes and how to put them right

• Saying a leaky valve blocks blood flow.

  Put it right: A leaky valve allows backflow because it does not seal properly.

• Confusing a valve that cannot open fully with a leaky valve.

  Put it right: The first restricts forward flow, the second allows reverse flow.

• Assuming all replacement valves last equally well.

  Put it right: Biological valves tend to wear out sooner, while mechanical valves are more durable but may need medication to reduce clotting.

Exam tips

• Use the phrase 'blood flows backwards' for a leaky valve and 'blood cannot flow through easily' for a valve that cannot open fully.
• When asked about consequences, link the faulty valve to the heart working harder and to symptoms such as breathlessness or tiredness.
• For treatment questions, compare biological and mechanical valves using one advantage and one disadvantage of each.