Coronary Heart Disease and Health

Coronary heart disease (CHD) is one of the leading causes of death in the UK. This lesson covers the causes, effects and treatments of CHD, as well as the broader concept of health and the link between lifestyle and non-communicable diseases, as required by the AQA GCSE Combined Science Trilogy specification (8464).

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What Is Health?

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."

This means health is more than just "not being ill" — it includes mental health and social well-being too.

Types of Disease

Type	Definition	Examples
Communicable	Caused by pathogens (bacteria, viruses, fungi, protists) and can be spread from person to person	Influenza, tuberculosis, HIV, malaria
Non-communicable	NOT caused by pathogens and CANNOT be spread between people	Coronary heart disease, cancer, type 2 diabetes, liver disease

Exam Tip: Non-communicable diseases are often linked to lifestyle factors such as diet, smoking, alcohol consumption and lack of exercise. These are sometimes called "lifestyle diseases."

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Coronary Heart Disease (CHD)

What Is CHD?

The coronary arteries supply the heart muscle with oxygenated blood and nutrients it needs for aerobic respiration and contraction.

In CHD, layers of fatty material (including cholesterol) build up inside the coronary arteries. This process is called atherosclerosis.

graph LR
    A["Healthy coronary artery — wide lumen"] --> B["Fatty deposits build up on artery wall"]
    B --> C["Lumen narrows — blood flow restricted"]
    C --> D["Heart muscle receives less oxygen and glucose"]
    D --> E["Reduced aerobic respiration in heart muscle"]
    E --> F["Angina (chest pain) or heart attack"]

Risk Factors for CHD

Risk Factor	How It Increases Risk
High-fat diet (especially saturated fat)	Increases blood cholesterol levels, leading to fatty deposits in arteries
Smoking	Damages artery walls, making fatty deposits more likely; carbon monoxide reduces oxygen-carrying capacity of blood
Lack of exercise	Increases blood pressure and cholesterol levels; reduces fitness of the heart
Obesity	Linked to high cholesterol, high blood pressure and type 2 diabetes
Genetic factors	Some people inherit a tendency to high cholesterol or high blood pressure
High blood pressure	Damages artery walls, increasing the risk of fatty deposits
Stress	Can raise blood pressure over time
Age and sex	Risk increases with age; males are at higher risk at younger ages

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Treatments for CHD

1. Stents

A stent is a small mesh tube inserted into a narrowed or blocked coronary artery to hold it open and restore blood flow.

Advantages	Disadvantages
Quick procedure (usually under local anaesthetic)	Risk of blood clot forming on the stent (patient may need to take anti-clotting medication)
Effective at restoring blood flow immediately	Does not address the underlying cause (lifestyle factors)
Less invasive than heart surgery	The artery can narrow again over time (re-stenosis)
Patient can recover quickly	Risk of infection or complications during the procedure

2. Statins

Statins are drugs that reduce the level of cholesterol in the blood by blocking an enzyme in the liver that produces cholesterol. They are taken long-term (usually daily).

Advantages	Disadvantages
Reduce blood cholesterol effectively	Must be taken regularly for life
Lower the risk of heart attacks, strokes and CHD	Can cause side effects (e.g. muscle pain, headaches, digestive problems)
Widely available and relatively cheap	May give a false sense of security — patients may think they can eat unhealthily
Proven to save lives in large clinical trials	Do not address all risk factors (e.g. smoking, lack of exercise)

3. Heart Transplant

In severe cases of heart failure (where the heart can no longer pump blood effectively), a heart transplant may be needed — replacing the diseased heart with a healthy donor heart.

Advantages	Disadvantages
Can save the life of a patient with heart failure	Limited supply of donor hearts — long waiting lists
The transplanted heart can function normally	Risk of rejection — the immune system may attack the new heart
Long-term solution	Patient must take immunosuppressant drugs for life (these weaken the immune system, increasing risk of infection)
	Major surgery with risks of complications

4. Artificial Hearts

An artificial heart is a mechanical device that can temporarily take over the function of a damaged heart while a patient waits for a transplant.

Advantages	Disadvantages
Can keep a patient alive while waiting for a donor heart	Only a temporary solution
No risk of rejection by the immune system (no foreign biological tissue)	Risk of blood clots forming — patient needs anti-clotting medication
Available when donor hearts are not	Risk of infection where the device is connected to the body
	Powered by batteries — mechanical failure is possible

5. Replacement Heart Valves

If heart valves become leaky (don't close properly) or stiff (don't open fully), they can be replaced with:

• Biological valves (from human donors or pigs/cows) — may need replacing over time
• Mechanical valves (made of metal or polymers) — last longer but require anti-clotting medication

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Non-Communicable Diseases and Risk Factors

Many non-communicable diseases share common risk factors:

Risk Factor	Associated Diseases
Smoking	CHD, lung cancer, chronic obstructive pulmonary disease (COPD), stroke
Obesity	Type 2 diabetes, CHD, some cancers, joint problems
Excessive alcohol	Liver disease, liver cancer, CHD, brain damage
Lack of exercise	CHD, obesity, type 2 diabetes, depression
Poor diet	CHD, type 2 diabetes, obesity, some cancers, malnutrition