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Animal Tissues, Organs and Systems » Coronary Heart Disease and Its Treatments

What you'll learn this session

Study time: 30 minutes

AQA spec: 4.2.2.4

What coronary heart disease is and how it harms the heart muscle
How stents and statins treat it
What faulty heart valves do and how they are replaced
How transplants and artificial hearts help in heart failure, and how to weigh up each treatment

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Coronary heart disease

Remember, the coronary arteries are the blood vessels that feed the heart muscle itself. The heart muscle needs a constant supply of oxygen to keep beating.

Coronary heart disease happens when layers of fatty material build up inside the coronary arteries. The arteries become narrower. Less blood can flow through them, so the heart muscle gets less oxygen. Without enough oxygen, the muscle cannot work properly.

Coronary heart disease is a non-communicable disease. This means it cannot be passed from one person to another.

Key terms:

Coronary heart disease: a disease in which layers of fatty material build up inside the coronary arteries and narrow them.
Cholesterol: a fatty substance in the blood. High levels lead to fatty deposits in the arteries.
Stent: a tube that is placed inside an artery to keep it open.
Statin: a drug that lowers the level of cholesterol in the blood.

Treating narrowed arteries

🔧 Stents

A stent is a small mesh tube. It is placed inside the narrowed coronary artery and holds it open, so blood can flow to the heart muscle again.

💊 Statins

Statins are widely used to reduce the level of cholesterol in the blood. This slows down the rate at which fatty material is deposited in the arteries.

Notice that they do different jobs. A stent opens an artery that is already narrow. A statin slows down the build-up of fatty material.

Advantages and disadvantages:

Stents: they work quickly and keep the artery open. But they need an operation, there is a risk of infection or bleeding, and a blood clot can form on the stent.
Statins: they are tablets that are easy to take and they reduce the risk of the disease getting worse. But they must be taken for a long time, and some people get side effects such as muscle pain or headaches. Statins slow the build-up. They do not clear the fatty material that is already there.

Faulty heart valves

The heart has valves that keep blood flowing in one direction. In some people a valve becomes faulty in one of two ways:

The valve does not open fully. Blood struggles to get through, so less blood is pumped out.
The valve develops a leak. Some blood flows backwards, so the heart is less efficient.

Either way, less oxygenated blood reaches the body for each beat. The heart has to work harder. A person may feel tired and short of breath.

A faulty valve can be replaced. There are two types of replacement:

🌿 Biological valve

This is taken from an animal, or from a human donor. It does not usually cause clots, but it wears out in time and may need replacing again.

⚙ Mechanical valve

This is made from man-made materials such as metal or plastic. It lasts a long time, but it can cause blood clots, so the patient needs drugs to stop the blood clotting.

Heart failure

In heart failure the heart can no longer pump blood well enough. Two treatments are used.

Transplant: a donor heart, or a donor heart and lungs together, is given to the patient. The patient needs to take drugs for the rest of their life so that the body does not reject the new organ. There are also not enough donors for everyone who needs one.
Artificial heart: a mechanical pump that does the job of the heart. Artificial hearts are only occasionally used. They keep a patient alive while waiting for a donor heart, or they allow the heart to rest as an aid to recovery.

Evaluating treatments

You may be asked to weigh up the advantages and disadvantages of treating cardiovascular diseases by drugs, mechanical devices or transplant.

💊 Drugs

Good: no major operation. Bad: they may need to be taken for years, can cause side effects, and do not always cure the problem.

⚙ Mechanical devices

Good: a stent or valve can restore blood flow quickly. Bad: they need surgery and can cause clots or infection.

❤ Transplants

Good: can replace a failing organ completely. Bad: a major operation, a shortage of donors, and a risk of rejection.

Worked example

A patient has a faulty heart valve that leaks. Doctors could replace it with a mechanical valve or a biological valve. A mechanical valve lasts for a long time, so a younger patient may not need another operation. But the patient must take drugs to stop clots forming. A biological valve needs no such drugs, but it may wear out and have to be replaced again. The choice depends on the patient.

Common mistakes

1. Saying coronary heart disease is caused by a germ. It is non-communicable.
2. Saying statins "unblock" arteries. They lower cholesterol and slow the build-up.
3. Mixing up the two valve faults. One will not open fully, the other leaks.
4. Saying an artificial heart is a permanent cure. It is occasionally used to keep a patient alive while waiting for a donor heart, or to let the heart rest.
5. Writing only advantages. An evaluation needs both sides.

Exam-style question

(a) Describe how coronary heart disease reduces the supply of oxygen to the heart muscle. [2 marks]

(b) Explain how a stent helps a patient with coronary heart disease. [2 marks]

Model answer

(a) Fatty material builds up inside the coronary arteries (1); this narrows the arteries, so less blood flows to the heart muscle and it gets less oxygen (1).

(b) It holds the artery open (1); so blood can flow through to the heart muscle again (1).

Exam tip

In "explain how" questions, say what the device does and then what that allows. "Holds the artery open" earns one mark. "So blood can flow to the heart muscle" earns the second.

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