Coronary heart disease: a non-communicable disease — AQA GCSE Biology
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Coronary heart disease: a non-communicable disease explained
Cardiovascular disease can be treated in three broad ways.
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Drugs such as statins lower blood cholesterol and reduce fatty deposits, while antihypertensives lower blood pressure; they are usually non-invasive and can be taken long term, but may cause side effects and must be taken regularly. Mechanical devices include stents, which hold narrowed coronary arteries open, and artificial pacemakers, which correct abnormal heart rhythms; they can be fitted quickly and improve blood flow, but carry surgical risks and may need replacement. A heart transplant replaces a damaged heart, offering the chance of a full recovery, but donor hearts are scarce, the operation is major and immunosuppressant drugs must be taken for life. Evaluation means weighing benefits against risks and limitations for a particular patient, not simply listing treatments.
In coronary heart disease layers of fatty material build up inside the coronary arteries, narrowing them.
The coronary arteries supply oxygenated blood to the heart muscle itself. In coronary heart disease, fatty material, mainly cholesterol, builds up in layers inside the walls of these arteries. This deposit narrows the lumen, so blood flow to the heart muscle is reduced. Less oxygen reaches the cardiac muscle, so aerobic respiration is limited and the muscle cannot contract as effectively. This can cause chest pain, called angina, and if an artery becomes completely blocked, part of the heart muscle is deprived of oxygen and may die, causing a heart attack. Risk factors include a diet high in saturated fat, smoking, high blood pressure and lack of exercise. Treatments aim to restore blood flow, for example by using stents or bypass surgery, or to reduce the fatty build-up with statins.
This reduces the flow of blood through the coronary arteries, resulting in a lack of oxygen for the heart muscle.
The coronary arteries branch from the aorta and supply the heart muscle itself with oxygenated blood. In coronary heart disease, fatty material called atheroma builds up in the artery wall, narrowing the lumen. This reduces the flow of blood through the coronary arteries, so less oxygen reaches the heart muscle cells. The heart muscle therefore has to respire anaerobically, which produces lactic acid and causes pain (angina). If a coronary artery becomes completely blocked, part of the heart muscle is starved of oxygen and dies, causing a heart attack. The narrowing is a gradual process linked to risk factors such as a high-fat diet, smoking and lack of exercise.
Stents are used to keep the coronary arteries open.
A stent is a small mesh tube inserted into a narrowed coronary artery during a procedure called angioplasty. A balloon catheter is guided to the narrowed section, the balloon is inflated to push the atheroma aside, and the stent expands and stays in place to hold the artery open. This restores blood flow through the coronary artery, so the heart muscle receives more oxygen and glucose. Stents can relieve angina and reduce the risk of a heart attack. They act quickly and are a local treatment, but they do not lower blood cholesterol, so the underlying disease process can continue and further narrowing may occur elsewhere.
Statins are widely used to reduce blood cholesterol levels which slows down the rate of fatty material deposit.
Statins are medicines taken regularly, usually as tablets, that reduce the level of cholesterol in the blood. Cholesterol is a fatty substance carried in the blood; a high level is linked to the build-up of fatty material, called atheroma, in artery walls. By lowering blood cholesterol, statins slow down the rate at which this fatty material is deposited in the coronary arteries. Slower deposition means the lumen narrows more slowly, so blood flow and oxygen supply to the heart muscle are maintained for longer and the risk of angina and heart attack is reduced. Statins are widely used because they are effective and relatively easy to take, but they must be taken long term and can cause side effects such as muscle pain.
In some people heart valves may become faulty, preventing the valve from opening fully, or the heart valve might develop a leak.
Heart valves keep blood flowing in one direction through the heart. The atrioventricular valves separate the atria from the ventricles, and the semilunar valves sit at the exits of the ventricles. In some people a valve may become faulty. If it cannot open fully, it is narrowed or stiff, so blood cannot flow through easily and the heart must work harder to push blood past it. If a valve develops a leak, it does not close completely, so blood flows backwards instead of moving on. Both faults reduce the efficiency of the heart, may cause breathlessness and tiredness, and can be treated by replacing the valve with a mechanical or biological valve.
Students should understand the consequences of faulty valves.
Heart valves are flap-like structures that keep blood flowing one way through the heart. The atrioventricular valves sit between atria and ventricles, and the semilunar valves sit between ventricles and the arteries leaving the heart. When a valve is faulty, it may not close fully, so blood leaks backwards, or it may become narrowed, so blood is forced through a smaller opening. Either problem means the heart must work harder to move the same volume of blood, which can cause breathlessness, tiredness, dizziness and swelling from fluid retention. A common example is a leaky mitral valve allowing blood to flow back into the left atrium during ventricular contraction. Students should link the structural fault to the direction of blood flow and to the extra work done by the heart.
Faulty heart valves can be replaced using biological or mechanical valves.
When a valve cannot be repaired, surgeons can replace it with a biological valve, taken from an animal such as a pig or cow, or from a human donor, or with a mechanical valve made from materials such as metal or polymer. Biological valves tend to work well without long-term anticoagulant medicine, but they may wear out sooner. Mechanical valves are very durable, but they increase the risk of blood clots, so patients usually need anticoagulant medicine for life. The choice depends on factors such as the patient's age, lifestyle, the valve position and the balance between durability and the risks of long-term medication. Students should compare the two types and explain why the decision is not the same for every patient.
In the case of heart failure a donor heart, or heart and lungs can be transplanted.
Heart failure means the heart cannot pump blood effectively enough to meet the body's needs. In severe cases, a patient may receive a donor heart, or a donor heart and lungs together if the lungs are also failing. The donor organ must come from a person who has died and whose family has agreed to donation, and it must be matched to the recipient to reduce the risk of rejection. The patient needs immunosuppressant medicine, often for life, to stop the immune system attacking the donated organ. Transplantation can greatly improve quality of life, but donor organs are scarce, and there are risks from surgery, infection and rejection. Students should explain both the benefits and the limitations.
Artificial hearts are occasionally used to keep patients alive whilst waiting for a heart transplant, or to allow the heart to rest as an aid to recovery.
An artificial heart is a mechanical pump that takes over some or all of the work of the heart. It is used only occasionally because it is a major operation and carries risks such as infection, bleeding and blood clots. One important use is as a bridge to transplant: the device keeps blood circulating while the patient waits for a suitable donor heart. Another use is to rest the patient's own heart, giving it time to recover after severe illness or surgery. Artificial hearts can improve survival and quality of life in the short term, but they are not a routine cure and may need an external power supply. Students should explain both purposes and the reasons the device is used only occasionally.
Your focus
- Describe how drugs, mechanical devices and transplants are used to treat cardiovascular disease.
- Compare the advantages and disadvantages of each treatment option.
- Reach and justify a treatment recommendation using the evidence provided.
Show all 30 objectives
- Describe how fatty material builds up in the coronary arteries and narrows them.
- Explain how reduced blood flow leads to angina and heart attack.
- Link coronary heart disease to named risk factors and to treatments that restore blood flow.
- Describe how narrowing of the coronary arteries reduces blood flow to the heart muscle.
- Explain why a reduced oxygen supply can damage heart muscle.
- Link coronary heart disease to named risk factors and to the symptoms it causes.
- Describe what a stent is and how it is used to treat narrowed coronary arteries.
- Explain how a stent improves blood flow and oxygen supply to the heart muscle.
- Evaluate the benefits and limitations of stents compared with other treatments.
- State what statins are and how they affect blood cholesterol.
- Explain how lowering cholesterol slows the deposition of fatty material in coronary arteries.
- Compare statins with stents in terms of how they reduce the risk of heart disease.
- Describe the two ways in which a heart valve can become faulty.
- Explain how a valve that cannot open fully or that leaks affects blood flow and heart function.
- State how faulty heart valves can be treated.
- Describe how heart valves normally maintain one-way blood flow.
- Explain how a leaky or narrowed valve changes blood flow and increases the heart's workload.
- Relate faulty valve function to named symptoms and to the need for treatment.
- Describe what biological and mechanical heart valves are made from.
- Compare the advantages and disadvantages of biological and mechanical valves.
- Explain how patient factors influence the choice of replacement valve.
- Describe when a donor heart or heart and lungs transplant may be used.
- Explain why immunosuppressant medicine is needed after transplantation.
- Evaluate the benefits and limitations of heart and heart-lung transplantation.
- Describe what an artificial heart is and how it supports circulation.
- Explain the two main situations in which an artificial heart may be used.
- Evaluate why artificial hearts are used only occasionally rather than routinely.
Coronary heart disease: a non-communicable disease exam tips
Marking Points
- Drugs such as statins reduce cholesterol and antihypertensives reduce blood pressure, but may cause side effects and require long-term adherence.
- Mechanical devices such as stents keep coronary arteries open and pacemakers regulate heart rhythm, but involve surgery and possible replacement.
- Heart transplant can restore heart function but depends on donor availability and requires lifelong immunosuppressant drugs.
- A good evaluation compares advantages and disadvantages and reaches a justified judgement for a given patient or situation.
- Answers should distinguish between treating symptoms, reducing risk and replacing a damaged organ.
- Fatty material, mainly cholesterol, builds up in layers inside the coronary arteries.
- The build-up narrows the lumen of the coronary arteries and reduces blood flow to the heart muscle.
- Reduced blood flow lowers oxygen supply to cardiac muscle, limiting aerobic respiration and contraction.
- Consequences include angina and, if an artery is blocked, a heart attack where heart muscle dies.
- Coronary heart disease is non-communicable and is linked to risk factors such as a high saturated fat diet, smoking and high blood pressure.
- The coronary arteries supply oxygenated blood to the heart muscle cells.
- Atheroma (fatty material) builds up in the coronary artery wall and narrows the lumen.
- A narrowed lumen reduces the volume of blood flowing through the coronary arteries.
- Reduced blood flow delivers less oxygen to the heart muscle.
- Without enough oxygen the heart muscle cannot respire aerobically and may be damaged or die.
- A complete blockage can cause a heart attack (myocardial infarction).
- A stent is a mesh tube inserted into a coronary artery.
- It is used to hold open an artery that has been narrowed by fatty material.
- Insertion usually involves a balloon catheter that is inflated to widen the artery.
- Restoring the lumen increases blood flow to the heart muscle.
- This improves oxygen supply, which can relieve angina and reduce heart attack risk.
- Stents do not reduce blood cholesterol, so they treat the narrowing rather than its cause.
- Statins are drugs that reduce the level of cholesterol in the blood.
- Cholesterol is a fatty substance associated with the build-up of atheroma in artery walls.
- Lower blood cholesterol slows the rate at which fatty material is deposited in the coronary arteries.
- Slower deposition means the coronary arteries narrow more slowly.
- This helps maintain blood flow and oxygen supply to the heart muscle.
- Statins are taken long term and may cause side effects, so benefits and risks must be weighed.
- Heart valves normally keep blood flowing in one direction through the heart.
- A faulty valve may fail to open fully, which restricts the flow of blood through it.
- A faulty valve may leak, allowing blood to flow backwards.
- Both faults mean the heart must work harder to maintain circulation.
- Symptoms can include breathlessness, tiredness and reduced exercise tolerance.
- Faulty valves can be replaced with mechanical or biological valves.
- Valves normally prevent backflow by closing between contractions, so blood travels in one direction through the heart.
- A faulty valve may fail to close completely, allowing blood to leak backwards, or may be narrowed, restricting forward flow.
- Backflow or restricted flow reduces the efficiency of the heart, so the heart must contract more forcefully or more often.
- Consequences can include breathlessness, tiredness, dizziness, fainting and swelling caused by fluid retention.
- The extra workload can lead to further heart problems, and severe cases may require treatment such as valve replacement.
- A faulty valve can be replaced with a biological valve from an animal or human donor, or with a mechanical valve made from artificial materials.
- Biological valves generally do not require lifelong anticoagulant medicine, but they may deteriorate and need replacing sooner.
- Mechanical valves are durable and long-lasting, but they carry a higher risk of blood clots, so anticoagulant medicine is often needed.
- The choice of valve depends on patient factors such as age, lifestyle, the position of the valve and the risks of surgery or medication.
- Valve replacement aims to restore one-way blood flow and reduce the extra workload on the heart.
- Heart failure occurs when the heart cannot pump blood effectively enough to meet the body's needs.
- A donor heart may be transplanted in severe heart failure, and a heart and lungs may be transplanted together when both organs are failing.
- Donor organs come from people who have died and whose organs have been donated, and matching reduces the risk of rejection.
- Immunosuppressant medicine is needed to reduce the chance of the immune system rejecting the transplanted organ.
- Transplantation can improve survival and quality of life, but donor organs are limited and there are risks such as infection and rejection.
- An artificial heart is a mechanical pump that circulates blood when the natural heart cannot do so effectively.
- It can be used as a bridge to transplant, keeping the patient alive until a suitable donor heart becomes available.
- It can also be used to rest the natural heart, allowing it time to recover after severe illness or surgery.
- Artificial hearts are used only occasionally because of risks such as infection, bleeding, blood clots and the need for a power supply.
- They can improve survival and quality of life in the short term, but they are not a permanent replacement for a healthy heart in most cases.
Examiner Tips
- 💡Use comparative connectives such as whereas, however and therefore to weigh up each option.
- 💡Refer to the specific patient context if one is given, for example age, lifestyle or severity of disease.
- 💡Finish with a justified conclusion rather than leaving the reader to decide.
- 💡Name the coronary arteries and state that they supply the heart muscle with oxygenated blood.
- 💡Link the narrowed lumen to reduced oxygen supply and then to angina or heart attack.
- 💡Use the term lumen when describing the space inside an artery.
- 💡Use the phrase 'reduces blood flow' and then link it explicitly to 'less oxygen reaches the heart muscle' to secure both parts of the statement.
- 💡When asked to explain, work through the chain: atheroma → narrowed lumen → reduced flow → less oxygen → anaerobic respiration → pain or damage.
- 💡If a question asks for a treatment, do not describe the cause in detail; keep the cause explanation brief and focus on the named treatment.
- 💡Name the artery and the direction of benefit: state that the stent keeps the coronary artery open so more blood reaches the heart muscle.
- 💡Compare stents with statins when asked: stents give rapid relief at one site, whereas statins reduce cholesterol and slow the disease process.
- 💡Avoid describing the surgical steps in unnecessary detail; one sentence on balloon inflation is enough unless the question specifically asks how it is inserted.
- 💡Use the causal chain 'statins lower blood cholesterol → less fatty material deposited → slower narrowing of coronary arteries'.
- 💡When comparing treatments, state that statins act on the cause of the disease process, whereas stents act on an existing blockage.
- 💡If asked about drawbacks, mention that statins must be taken regularly for a long time and can have side effects.
- 💡Use the two clear categories from the statement: a valve that cannot open fully restricts flow, and a valve that leaks allows backflow.
- 💡Link each fault to its consequence: restricted flow or backflow means the heart works harder and less blood is pumped efficiently.
- 💡If asked about treatment, name valve replacement and state that mechanical and biological valves are both used.
- 💡Name the valve and the chamber or vessel on each side of it so your description of backflow is precise.
- 💡Use the phrase one-way flow and explain what happens when it is not maintained.
- 💡Link each consequence to the extra work done by the heart rather than listing symptoms without explanation.
- 💡Compare the two valve types using at least one advantage and one disadvantage for each.
- 💡Refer to anticoagulant medicine rather than vaguely saying blood-thinning drugs.
- 💡Link the purpose of replacement back to restoring one-way flow and reducing strain on the heart.
- 💡State clearly when a heart and lungs are transplanted together rather than a heart alone.
- 💡Include both a benefit and a limitation of transplantation to show balanced understanding.
- 💡Use the term immunosuppressant medicine and link it to reducing rejection.
- 💡State the two main purposes of an artificial heart: bridge to transplant and resting the heart to aid recovery.
- 💡Use the phrase occasionally used and give a reason why it is not routine.
- 💡Link the device to circulation, explaining that it maintains blood flow around the body.
Common Mistakes
- Listing treatments without comparing advantages and disadvantages; correct this by making a clear judgement supported by the points given.
- Claiming transplants cure heart disease with no ongoing treatment; correct this by stating that immunosuppressant drugs are needed for life.
- Treating all drugs as risk-free; correct this by mentioning possible side effects and the need for regular use.
- Saying fatty material builds up in the heart chambers; correct this by stating it builds up inside the coronary arteries.
- Confusing narrowing with complete blockage; correct this by explaining that narrowing reduces flow, while a blockage can cause a heart attack.
- Thinking the coronary arteries carry deoxygenated blood; correct this by stating they supply oxygenated blood to the heart muscle.
- Confusing the coronary arteries with the coronary veins: the arteries carry oxygenated blood to the heart muscle, so the error is naming the wrong vessel; the correction is to state that the coronary arteries deliver oxygen and glucose to the heart muscle.
- Thinking the heart muscle is supplied by blood inside the chambers: the error is that blood in the chambers does not nourish the muscle; the correction is that the coronary arteries branch from the aorta and supply the muscle directly.
- Saying the heart stops beating immediately when an artery narrows: the error is overstating the effect; the correction is that narrowing reduces oxygen supply and causes pain, while a complete blockage can cause a heart attack.
- Saying a stent dissolves the fatty material: the error is that a stent does not remove atheroma; the correction is that it pushes the lining aside and holds the artery open.
- Confusing a stent with a statin: the error is mixing a mechanical device with a medicine; the correction is that a stent is a physical tube inserted into the artery, while a statin is a drug that lowers cholesterol.
- Claiming a stent cures coronary heart disease permanently: the error is overstating the effect; the correction is that a stent relieves the blockage at that site but does not stop further fatty deposits forming.
- Saying statins widen the arteries: the error is that statins do not mechanically open vessels; the correction is that they lower cholesterol, which slows further fatty deposit.
- Confusing cholesterol with glucose: the error is treating them as the same substance; the correction is that cholesterol is a fatty substance carried in the blood, while glucose is a sugar used in respiration.
- Claiming statins remove existing atheroma: the error is overstating the effect; the correction is that statins slow the rate of new fatty material being deposited.
- Saying a leaky valve blocks blood flow completely: the error is confusing a leak with a blockage; the correction is that a leak allows backflow, while a valve that cannot open fully restricts forward flow.
- Mixing up the atrioventricular and semilunar valves: the error is naming the wrong valve position; the correction is to state that atrioventricular valves lie between atria and ventricles, and semilunar valves lie at the exits of the ventricles.
- Thinking faulty valves stop the heart beating: the error is overstating the effect; the correction is that the heart still beats but works less efficiently, causing symptoms such as breathlessness.
- Thinking that a faulty valve stops blood flowing altogether; the error is ignoring that leakage or narrowing usually reduces rather than blocks flow, so the correction is to describe reduced efficiency and backflow.
- Confusing the direction of leakage, for example saying blood leaks from the atrium into the ventricle when the atrioventricular valve fails; the correction is that blood leaks backwards from the ventricle into the atrium.
- Assuming faulty valves only affect the heart and not the rest of the body; the correction is to link poor circulation to symptoms such as breathlessness, tiredness and swelling.
- Stating that biological valves never need replacing; the correction is that they can wear out over time, especially in younger, more active patients.
- Claiming that mechanical valves need no medication; the correction is that anticoagulants are usually required to reduce clot risk.
- Treating one valve type as always better; the correction is that the best choice depends on the individual patient and the balance of benefits and risks.
- Saying a donor heart is grown or made artificially; the correction is that a donor heart comes from a person who has died and donated their organs.
- Forgetting that immunosuppressant medicine is needed after transplantation; the correction is that it reduces the risk of rejection by the immune system.
- Assuming transplantation is always available; the correction is that donor organs are scarce, so patients may wait a long time and some do not receive one.
- Confusing an artificial heart with a donor heart; the correction is that an artificial heart is a mechanical pump, whereas a donor heart comes from an organ donor.
- Thinking an artificial heart is a permanent cure for everyone; the correction is that it is usually a temporary measure, used as a bridge to transplant or to rest the heart.
- Ignoring the risks of artificial hearts; the correction is to mention problems such as infection, bleeding, clotting and the external power supply.