Coronary Heart Disease

Coronary heart disease (CHD) is a non-communicable disease — it is not caused by a pathogen and cannot be passed from person to person.

The coronary arteries are the blood vessels that supply the heart muscle itself with oxygenated blood. In CHD, layers of fatty material build up inside the coronary arteries, narrowing them. This narrowing reduces the flow of blood through the arteries, so the heart muscle receives less oxygen.

Heart muscle needs a constant oxygen supply to respire and keep contracting. Starve it of oxygen and the consequences follow in a chain:

• Narrowed artery → reduced blood flow → less oxygen reaching the heart muscle
• Less oxygen → less aerobic respiration → the muscle cannot release enough energy to contract properly
• A fully blocked coronary artery → that region of heart muscle dies → a heart attack (myocardial infarction)

Key definition: Coronary heart disease is the narrowing of the coronary arteries by fatty deposits, reducing the supply of oxygenated blood to the heart muscle.

The rest of this lesson covers the treatments AQA asks you to know — stents, statins, replacement valves, transplants and artificial hearts — and how to evaluate each one.

A stent is a small mesh tube that is inserted into a narrowed coronary artery and expanded to push the artery wall open. It is a mechanical, surgical solution: it physically widens the vessel so blood can flow normally again.

Feature	Detail
How it works	Mesh tube widens the artery and keeps it open, restoring blood flow to the heart muscle
Advantages	Effective for a long time; the recovery time from surgery is relatively quick
Disadvantages	Surgery carries risks (bleeding, infection); blood clots can form near the stent (thrombosis); does not treat the underlying cause, so more fatty deposits can still build up elsewhere

The most important evaluation point: a stent widens one narrowed section. It does nothing to stop fatty material building up in the rest of the arteries, because it does not lower the patient's cholesterol.

Exam tip: Classify each treatment as a drug, a mechanical device, or a transplant — AQA frames the evaluation question (WS 1.3, 1.4) around those three categories. A stent is a mechanical device.

Statins are drugs that are widely used to reduce blood cholesterol levels. Lower cholesterol slows down the rate at which fatty material is deposited inside the arteries.

Unlike a stent, a statin is taken regularly over the long term — usually as a daily tablet for life. It tackles the cause of the fatty build-up across all the arteries, not just one narrowed section.

Feature	Detail
How it works	Reduces blood cholesterol, slowing the build-up of fatty deposits in the arteries
Advantages	Reduces the rate of fatty deposits everywhere, lowering the risk of CHD and other diseases; can also increase "good" cholesterol; no surgery needed
Disadvantages	Must be taken for a long time (lifelong) and the patient must remember to take them; can cause side effects such as headaches or, rarely, kidney or liver problems; effect is not immediate

Cholesterol is carried in the blood in two main forms. Lowering LDL ("bad") cholesterol is what reduces fatty deposits.

(Extra context — the LDL/HDL distinction is not required by AQA 8461; the spec asks only that statins reduce blood cholesterol.)

A patient has one badly narrowed coronary artery causing chest pain when they exercise. Their doctor weighs a stent against statins. Work through the comparison the way an exam answer should — point, then consequence.

Argument for the stent (mechanical):

• It physically widens the blocked section, so blood flow to the heart muscle is restored quickly.
• The chest pain is caused by that narrowing, so a stent directly relieves the symptom.

Argument for statins (drug):

• The fatty deposit is not just in one place — narrowing in one artery suggests the rest are at risk too.
• Statins lower cholesterol throughout the body, slowing build-up in every artery, not only the treated one.
• No surgery means no surgical risk of bleeding, infection or clotting.

The balanced conclusion: these treatments are not either/or. A stent gives immediate relief for the dangerous narrowing, while statins manage the long-term cause. Many patients are given a stent and prescribed statins. A good evaluation states a judgement and justifies it — here, that a stent addresses the urgent blockage while statins reduce the chance of new ones forming.

Exam tip: "Evaluate" means weigh advantages and disadvantages and reach a justified conclusion. A list of facts with no judgement loses the final marks.

Heart valves keep blood flowing in one direction through the heart, snapping shut to stop backflow. In some people a valve becomes faulty in one of two ways:

• It does not open fully — this restricts the flow of blood through the heart.
• It develops a leak — blood flows backwards through the valve, the wrong way.

Consequences of a faulty valve: the heart has to work harder to pump enough blood, and the body's tissues may not receive enough oxygenated blood. The person may feel breathless and tired. A faulty valve can be replaced with a biological or a mechanical valve.

Replacement valve	How it works	Advantages	Disadvantages
Biological (from a human donor, pig, cow or built from animal tissue)	Replaces the faulty valve with living/animal tissue	No need for lifelong anticoagulant drugs; behaves more like a natural valve	May wear out over time and need replacing again; tissue could be rejected
Mechanical (man-made)	Replaces the faulty valve with a durable artificial valve	Lasts a long time — often a lifetime	Patient must take anticoagulant (anti-clotting) drugs for life, because blood tends to clot on the mechanical surface

Key definition: Anticoagulant drugs reduce the blood's ability to clot. A clot forming on a mechanical valve could break off and block a vessel, so these drugs are essential for mechanical-valve patients.

Replacing a valve is less drastic than replacing the whole heart — the patient keeps their own heart, only the faulty valve is changed.

Two patients both need a valve replaced. The "best" choice depends on the patient, which is exactly what an evaluation should bring out.

Patient A — a 75-year-old:

• A biological valve may wear out after, say, 10–15 years — but at this age it may comfortably last the rest of their life, so durability is less of a concern.
• Avoiding lifelong anticoagulant drugs is valuable: those drugs raise the risk of dangerous bleeding, which is more serious in older patients.
• Judgement: a biological valve is often the better fit here.

Patient B — a 30-year-old:

• A biological valve would likely wear out and need replacing — meaning repeat open-heart surgery, each carrying its own risk.
• A mechanical valve can last for the rest of their life, avoiding repeat operations.
• The trade-off is taking anticoagulant drugs for decades and the lifestyle limits that brings.
• Judgement: a mechanical valve's durability often outweighs the inconvenience of the drugs.

The exam skill here is matching the disadvantage of each option to what matters most for that patient — durability versus the burden of lifelong medication — and then committing to a justified choice.

In heart failure the heart can no longer pump blood effectively around the body, and the damage is too severe for stents, statins or a valve replacement to fix. Two further options exist.

Transplant. A donor heart, or a donor heart and lungs together, can be transplanted from a person who has recently died.

Treatment	How it works	Advantages	Disadvantages
Heart (or heart and lung) transplant	The failing heart is replaced with a healthy donor organ	A permanent cure that can restore normal heart function	Shortage of donors; the body may reject the donor organ, so the patient needs immunosuppressant drugs for life; major surgery with serious risks
Artificial heart	A mechanical pump keeps blood circulating, used temporarily	Buys time waiting for a donor, or lets the natural heart rest and recover; not rejected as it is not living tissue, so fewer/no immunosuppressants needed	Surgery to fit it carries risks; blood does not flow as smoothly through the mechanical parts, so clots can form and the patient may need anticoagulant drugs; usually a short-term measure, not a permanent solution

Artificial hearts are mechanical devices used occasionally and as a temporary measure: either to keep a patient alive whilst they wait for a transplant, or to allow their own heart to rest as an aid to recovery so it can heal.

Exam tip: Note the wording precisely — artificial hearts are a temporary solution. Calling them a permanent cure is a common error.

1. Saying a stent or statin "cures" coronary heart disease

Neither cures CHD. A stent widens one narrowed section; statins slow the build-up of fatty deposits. Fatty material can still build up over time, so the disease is managed, not cured.

2. Confusing what stents and statins are

A stent is a mechanical device fitted by surgery. A statin is a drug taken as a long-term medicine. They are different treatments with similar-sounding names — be sure which one the question is asking about.

3. Forgetting the consequence of a faulty valve

Describe the effect, not just the fault: a valve that does not open fully restricts blood flow, and a leaky valve lets blood flow backwards. Both make the heart work harder and reduce oxygen delivery to the body.

4. Forgetting anticoagulant drugs for mechanical valves

A mechanical valve lasts longer than a biological one, but its key disadvantage is that the patient must take anticoagulant drugs for life to stop clots forming on it. Leaving this out misses the main trade-off.

5. Calling an artificial heart a permanent cure

Artificial hearts are used as a temporary measure — to keep a patient alive while waiting for a transplant, or to rest the heart while it recovers. A transplant, not an artificial heart, is the long-term replacement.

6. Listing facts but not evaluating

When a question says "evaluate", weigh the advantages against the disadvantages and reach a justified conclusion. Listing points on each side without committing to a judgement leaves marks on the table.