4.4 Helping the Heart

A free GCSE Biology lesson for AQA (8461) from OBA School: replacement valves, artificial pacemakers, artificial hearts and heart transplants. Watch the video, read the explanation and worked examples, then try the revision questions. You can work through the full lesson, with every video, practice quizzes and printable worksheets with mark schemes, in our free online course.

What you will learn

• Describe what happens when heart valves are faulty and compare biological and mechanical replacement valves
• Explain how an artificial pacemaker corrects an irregular heart rate
• Describe the use of heart transplants and artificial hearts in heart failure
• Evaluate the advantages and disadvantages of these treatments, including ethical and practical issues

Key words

• Faulty valve: A heart valve that does not open fully or that leaks, so blood flows the wrong way.
• Biological valve: A replacement valve made from animal tissue (often a pig or cow) or from a human donor.
• Mechanical valve: A replacement valve made from materials such as metal and carbon.
• Artificial pacemaker: A small battery-powered electrical device implanted in the chest that corrects an irregular heart rate.
• Heart failure: When the heart can no longer pump enough blood around the body.
• Anticoagulant: A drug that stops blood clots forming.
• Anti-rejection drug: An immunosuppressant: a drug that suppresses the immune system so a donor organ is not rejected.

Faulty heart valves

Heart valves keep blood flowing one way. With age or after an infection, a valve can become stiff (it does not open fully) or leaky (it does not close properly, so blood flows backwards). The heart then pumps less blood with each beat, so less oxygen reaches the body. People feel tired and breathless.

• Made from; Biological valve animal tissue (pig or cow) or a human donor; Mechanical valve metal, carbon or plastic materials
• How long it lasts; Biological valve about 10–20 years, then may need replacing; Mechanical valve can last a lifetime
• Medicines afterwards; Biological valve usually no long-term drugs; Mechanical valve anticoagulants for life, because blood can clot on the valve
• Other points; Biological valve some people object to using animal tissue; Mechanical valve may make a quiet clicking sound

Exam tip: Match the valve to the patient. An older patient may prefer a biological valve (no lifelong drugs, and it may outlast them); a younger patient may prefer a mechanical one so they avoid repeat surgery.

Artificial pacemakers

If the natural pacemaker in the right atrium does not work properly, the heart may beat too slowly or irregularly. An artificial pacemaker is a small battery-powered device placed under the skin of the chest, with a wire to the heart. It sends small electrical impulses that correct the rhythm.

• For: small operation, usually with a local anaesthetic; the patient can live a near-normal life.
• Against: regular check-ups; the battery must be replaced every few years; risk of infection; strong magnetic fields (such as an MRI scanner) can interfere with it.

Worked example: percentage change

Before a pacemaker, a patient's resting heart rate was 40 beats per minute. Afterwards it is 68 beats per minute. Calculate the percentage increase.
increase = 68 − 40 = 28
percentage increase = (28 ÷ 40) × 100 = 70%

Answer: 70% increase

Heart transplants and artificial hearts

In heart failure a patient may be given a heart transplant (or a heart and lungs transplant) from a donor who has died. Problems include a shortage of donors, long waiting times, the risks of major surgery, and rejection: the immune system attacks the new heart, so the patient takes immunosuppressant drugs for life, which makes infections more likely.

Artificial hearts are mechanical pumps. They are mostly used to keep a patient alive while they wait for a donor heart, or to give a diseased heart a rest so it can recover. They are not rejected by the immune system, but blood can clot in them (so anticoagulants are needed), there is a risk of infection, and some are powered by batteries carried outside the body.

Worked example: survival data

A hospital followed 250 transplant patients. After one year, 215 were still alive. What percentage survived for one year?
(215 ÷ 250) × 100 = 86%

Answer: 86%

Evaluating treatments

In evaluate questions, give points for and against each treatment, then a conclusion with a reason. Think about:

• how well it works and how long it lasts
• risks: surgery, infection, clots, rejection
• drugs needed afterwards and their side effects
• cost, and availability (donors)
• ethical issues: using animal tissue, how donor organs are shared out, consent

Key fact: Many patients with heart problems are also advised to change their lifestyle (stop smoking, eat less saturated fat, exercise more) to reduce the risk of further disease.

Common mistakes

• Saying mechanical valves need anti-rejection drugs. They need anticoagulants to stop clots; they are not rejected.
• Saying artificial hearts are a permanent cure. Most are used temporarily while waiting for a transplant or to let the heart rest.
• Confusing the natural pacemaker (cells in the right atrium) with an artificial pacemaker (an electrical device).
• Giving only advantages in an "evaluate" question. You need both sides and a justified conclusion.

Revision questions

Try these, then check your answers below each one.

Question 1. Which statement about mechanical replacement heart valves is correct? (Choose from: They are made from pig or cow tissue, They are usually rejected by the immune system, They wear out after about two years, They last a long time, but the patient must take anticoagulants for life.)

Answer: They last a long time, but the patient must take anticoagulants for life

Working: Mechanical valves can last a lifetime, but blood clots can form on them, so patients take anticoagulant drugs for life.

Question 2. True or false? A biological heart valve may need to be replaced after about 10 to 20 years.

Answer: True

Working: True. Biological valves usually do not need lifelong drugs, but they wear out sooner.

Question 3. What device can be fitted to correct an irregular heart rate?

Answer: artificial pacemaker

Working: An artificial pacemaker sends electrical impulses to the heart to correct its rhythm.

Related lessons

• Previous lesson: 4.3 The Heart
• Next lesson: 4.5 Breathing and Gas Exchange
• In this chapter: 4.1 The Blood
• In this chapter: 4.2 The Blood Vessels
• In this chapter: 4.6 Tissues and Organs in Plants

Continue in the full course

This lesson is section 4.4 (AGCBH0404) of our free GCSE Biology course for AQA. In the full course you get every video for this section, a self-marking practice quiz, a printable worksheet with a mark scheme, chapter tests, and your progress saved. Go to the full GCSE Biology course.