CHD: A Non-Communicable Disease (AQA GCSE Biology): Revision Note

Coronary heart disease

• The heart is made of cardiac muscle cells which need a supply of blood to deliver oxygen, glucose (for respiration) and other nutrients, and remove waste products such as carbon dioxide

• The blood is supplied to the heart by the coronary arteries which branch off directly from the aorta and sit on the outside of the heart

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What is coronary heart disease?

• Coronary heart disease (CHD) involves layers of fatty material (called plaque) building up inside the coronary arteries

• If a coronary artery becomes partially or completely blocked by these fatty deposits blood flow through the arteries is reduced

• This results in a lack of oxygen for the heart muscle

  • Partial blockage of the coronary arteries creates a restricted blood flow to the cardiac muscle cells and results in severe chest pains called angina

  • Complete blockage means cells in that area of the heart will not be able to respire aerobically, leading to a heart attack

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Treating coronary heart disease

• Treatment of CHD involves either:

  • increasing the width of the lumen of the coronary arteries using a stent

  • prescribing statins to lower blood cholesterol

Treating CHD: Stents

• Stents can be used to keep the coronary arteries open

  • A narrow tube is threaded up through the groin up to the blocked vessel

  • A tiny balloon is then inflated

  • The balloon pushes the metal or plastic stent against the wall of the artery, increasing the width of the lumen

  • The balloon and tube are then removed

• Stents are very effective at reducing the risk of a heart attack as they widen the lumen to increase blood flow to the coronary arteries, and the procedure is relatively simple

• Stents also last a long time, which is a positive, however, there is a risk of blood clots (thrombosis) occurring

Advantages and disadvantages of stents

How stents are inserted

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Treating CHD: Statins

• Statins are drugs that are widely used to reduce the levels of fatty deposits (cholesterol) in the blood

• They block an enzyme in the liver which is needed to make cholesterol

• This slows down the rate of fatty material building up in the blood, reducing the risk of CHD occurring

• There are many advantages and disadvantages of statins:

Advantages and disadvantages of statins

Faulty heart valves

• The heart valves play a vital role in ensuring blood is pumped from the ventricles to the arteries, in one direction only

• In some people, heart valves may become faulty as a result of illness, old age or a heart attack

• Valves can stiffen which can prevent them from opening fully to let blood flow through

  • This reduces the volume of blood pumped by the heart

• Sometimes a faulty heart valve might develop a leak

  • This allows blood to flow from the ventricles back into the atria or the arteries back into the ventricles

• Both issues reduce the effectiveness of the heart in pumping oxygenated blood around the body

• Faulty heart valves can be replaced via surgery using:

  • biological valves from cows or pigs

  • mechanical valves

Advantages and disadvantages of replacement valves

Heart transplants

• In the case of heart failure a heart can be transplanted from a donor who has recently died

• Waiting lists for organ transplants are often long, so an immediate solution can involve replacing the heart with an artificial heart made from plastic and metal

• Artificial hearts may be used to:

  • keep patients alive while waiting for a heart transplant 

  • allow the heart to rest as an aid to recovery

Advantages and disadvantages of artificial hearts