Risk Factors for Coronary Heart Disease (Edexcel IGCSE Biology: Double Science)

Causes of coronary heart disease

• Like all cells in the body, cardiac muscle cells need a supply of blood to deliver oxygen and glucose and to 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
  • The heart needs to constantly respire, so it is vital that it receives oxygen

The coronary arteries supply the heart with oxygenated blood

• In coronary heart disease (CHD), layers of fatty material (plaque) build up inside the coronary arteries
• These fatty deposits are mainly formed from cholesterol
• There are two sources of cholesterol in the body:
  • Dietary cholesterol (from animal products eaten)
  • Cholesterol synthesised by the liver

Buildup of plaque in the coronary arteries narrows the lumen

• If a coronary artery becomes partially or completely blocked by these fatty deposits, it loses its elasticity and cannot stretch to accommodate the blood which is being forced through every time the heart contracts
• The flow of blood through the arteries is reduced, resulting 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

• Treatment of CHD involves either increasing the width of the lumen of the coronary arteries using a stent, or prescribing statins to lower blood cholesterol

The effect of a narrowed lumen in a coronary artery is reduced blood flow to the heart

Risk factors of coronary heart disease

• There are several risk factors which will increase the chances of coronary heart disease:
• Obesity
  • Carrying extra weight puts a strain on the heart
  • Increased weight can lead to Type 2 diabetes which further damages your blood vessels

• High blood pressure
  • This increases the force of the blood against the artery walls and consequently leads to damage of the vessels

• High cholesterol
  • Speeds up the build up of fatty plaques in the arteries leading to blockages

• Smoking
  • Chemicals in smoke cause an increase in plaque build up and an increase in blood pressure
  • Carbon monoxide also reduces the oxygen carrying capacity of the red blood cells