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Coronary heart disease (CHD) is one of the most important non-communicable diseases covered in the AQA GCSE Biology specification. It is a leading cause of death in the UK and worldwide. In this lesson you will learn what coronary heart disease is, what causes it, how it is treated, and the wider concept of health and disease, including risk factors for non-communicable diseases.
The World Health Organisation (WHO) defines health as a state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity. For AQA GCSE Biology, you need to understand that health is more than just "not being ill."
| Dimension | Meaning |
|---|---|
| Physical health | The body is functioning normally, free from disease and injury |
| Mental health | A state of psychological well-being, the ability to cope with stress, and normal cognitive and emotional functioning |
| Social health | The ability to form and maintain relationships, participate in society, and have a sense of belonging |
All three dimensions interact. For example, a chronic physical illness can lead to poor mental health (depression, anxiety), which may in turn affect social health (isolation, relationship breakdown).
| Type | Definition | Examples |
|---|---|---|
| Communicable diseases | Diseases caused by pathogens that can be spread from person to person | Measles, tuberculosis, HIV, cholera |
| Non-communicable diseases (NCDs) | Diseases that are not caused by pathogens and cannot be passed from person to person | Coronary heart disease, cancer, type 2 diabetes, liver disease |
Non-communicable diseases are sometimes called lifestyle diseases because they are often linked to how people live — their diet, activity levels, alcohol intake and smoking habits.
Exam Tip: The AQA specification frequently asks about the interaction between communicable and non-communicable diseases. For example, a person with HIV (communicable) has a weakened immune system and is more likely to develop certain cancers (non-communicable). Be prepared to give examples of how one type of disease can make the other more likely.
A risk factor is something that increases the likelihood of developing a disease. Risk factors can be:
| Category | Examples |
|---|---|
| Lifestyle factors (things you can control) | Smoking, excessive alcohol consumption, poor diet, lack of exercise, drug misuse |
| Genetic factors (inherited) | Family history of heart disease, inherited gene mutations linked to certain cancers |
| Environmental factors | Air pollution, UV radiation, exposure to chemicals (carcinogens) |
| Disease | Key Risk Factors |
|---|---|
| Coronary heart disease | Smoking, high-fat diet (saturated fat), lack of exercise, obesity, high blood pressure, family history |
| Type 2 diabetes | Obesity, poor diet (excess sugar), lack of exercise, family history |
| Liver disease | Excessive alcohol consumption, hepatitis infection |
| Lung cancer | Smoking, exposure to asbestos, radon gas, air pollution |
| Skin cancer | Excessive UV exposure (sunlight, sunbeds), fair skin, family history |
Exam Tip: Risk factors show a correlation (a link) with disease, but correlation does not always mean causation. The exam may ask you to distinguish between these. For example, there is strong scientific evidence that smoking causes lung cancer (causal link), but for some risk factors the evidence may only show a correlation, not a proven direct cause.
Coronary heart disease (CHD) occurs when the coronary arteries — the blood vessels that supply the heart muscle itself with oxygenated blood — become narrowed or blocked.
graph TD
A[Fatty deposits build up in coronary artery walls] --> B[Lumen narrows — atherosclerosis]
B --> C[Reduced blood flow to heart muscle]
C --> D[Heart muscle receives less oxygen and glucose]
D --> E[Heart muscle cells cannot respire adequately]
E --> F[If artery is completely blocked — heart attack]
AQA requires you to know several treatments:
A stent is a small mesh tube that is inserted into a narrowed coronary artery to hold it open, allowing blood to flow more freely.
| Advantages | Disadvantages |
|---|---|
| Effective at keeping the artery open and restoring blood flow | Risk of blood clots forming on the stent (patient may need to take blood-thinning medication) |
| Relatively quick procedure (keyhole surgery) | Risk of complications during surgery (infection, bleeding) |
| Immediate improvement in blood flow | The artery may narrow again over time (restenosis) |
| Does not require major surgery | Does not address the underlying cause (lifestyle may still need to change) |
Statins are drugs that reduce the level of cholesterol in the blood, slowing down the rate at which fatty deposits build up in the arteries.
| Advantages | Disadvantages |
|---|---|
| Reduce blood cholesterol, lowering the risk of heart attack and stroke | Must be taken long-term (every day for life) |
| Widely available and relatively inexpensive | Can cause side effects (muscle pain, headaches, digestive problems) |
| Very effective when taken regularly | Some people forget to take them consistently |
| Can be used alongside lifestyle changes | Do not remove existing fatty deposits — they only slow further build-up |
In severe cases of heart disease, a heart transplant may be necessary — replacing the damaged heart with a healthy donor heart.
| Advantages | Disadvantages |
|---|---|
| Can save the life of a patient with end-stage heart failure | Shortage of donor hearts — long waiting lists |
| Restores full heart function | Major surgery with significant risks (infection, bleeding, organ rejection) |
| Long-term solution | Patient must take immunosuppressant drugs for life to prevent rejection, which increases susceptibility to infections |
An artificial heart is a mechanical device that can temporarily replace the function of the heart, usually while a patient waits for a donor heart transplant.
| Advantages | Disadvantages |
|---|---|
| Can keep a patient alive while waiting for a transplant | Only a temporary solution |
| No risk of rejection by the immune system | Surgery to fit the device is risky |
| Donor is not required | Parts can wear out, blood clots may form, risk of infection |
| Allows time for other treatments to work | Requires an external power source; restricts patient mobility |
If the heart valves become faulty (leaking or stiff), they can be replaced with:
Both types restore proper blood flow and prevent backflow. Mechanical valves last longer but require the patient to take blood-thinning drugs. Biological valves do not last as long and may need replacing.
Exam Tip: You may be asked to evaluate a treatment — this means giving advantages AND disadvantages. Always present both sides and, where possible, compare treatments (e.g. stents vs statins, biological vs mechanical valves).
The best approach to coronary heart disease is prevention:
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