Biological Basis of Heart Disease

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Coronary Heart Disease and Atheroma

Coronary Heart Disease (CDH) 

- Affects the coronary arteries which supply the heart muscle with oxygen and glucose needed for respiration


- Build up of fatty acids that form on the walls in the coronary arteries

- Begin as fatty streaks made up of white blood cells that have taken up LDL's (low-density lipoproteins)

- These enlarge to from an irregular patch, or atheromatous plaque

- These are made up of cholesterol, fibres, dead muscle cells

- Bulge into the lumen of the artery, causing it to narrow, restricting blood flow

Atheromas increases risk of two maybe dangerous conditions: THROMBOSIS and ANEURYSM

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Thrombosis, Aneurysm and Myocardial Infarction


  • If atheroma breaks lining of blood vessels, it forms rough surface that interrupts smooth flow of blood
  • May result in a blood clot, or THROMBUS which may block the blood vessel, preventing blood flow to tissues beyond it, or blood vessel, and lack of oxygen, nutrients + glucose, so it dies


  • Atheromas that lead to formation of thrombosis also weaken the artery walls
  • These points swell to form a blood filled structure (like a balloon) called an ANEURYSM
  • These frequently burst --> haemorrhage --> loss of blood to region of the body
  • A brain aneurysm is known as a cerbrovascular accident (CVA) or STROKE

Myocardial Infarction

  • Known as a HEART ATTACK
  • Reduced supply of oxygen to the heart muscle from a blockage in the coronary arteries
  • If occured close to junction of aorta and coronary artery - heart stop beating, no blood supply
  • If further away, milder symptoms because smaller area of muscle has been cut off
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Risk Factors Associated with CHD


  • Smokers are between x2 and x6 more likely to suffer from heart disease than non-smokers
  • Giving up is the most effective way of increasing life expectancy

2 Main Factors:


  • Combines easily + irreversibly with haemogloblin in red blood cells -> forms carboxyhaemoglobin, reducing oxygen-carrying capacity of the blood
  • This makes the heart work harder to supply the same amount of oxygen 
  • Can lead to increased blood pressure + increases risk of coronary heart diease and strokes
  • Lack of oxygen  while doing exercise can lead to chest pains (angina) or myocardial infarction


  • Stimulates production of hormone adrenaline -> increase heart rate + raises blood pressure
  • Also makes platelets in blood more 'sticky' -> higher risk of thrombosis
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Risk Factors Associated with CHD cont. 2

High Blood Pressure

  • Genes can cause this, which cannot be changed by altering your lifestlye
  • But lifestyle choices can increase your blood pressure such as:
    • Prolonged stress
    • Certain diets
    • Lack of excerise

Increases it because:

  • Already high blood pressure in arteries, the heart must work harder to pump blood into them   ->  increasing risk of failure --> more likely to develop aneurysm, then burst -> haemorrhage 
  • To resist the higher pressure within them, walls of arteries tend to become thicker and harden, restricting blood flow 
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Risk Factors Associated with CHD cont. 3

Blood Cholesterol

  • Cholesterol is important component of membranes, so must be transported in the blood
  • It is carried in the plasma in tiny spheres of lipoproteins (lipid + proteins)

Two Types:

High-Density Lipoprotein (HDLs) 

  • Remove cholesterol from tissues, transports it to liver for excretion. Protect arteries against heart diseases

Low-Density Lipoprotein (LDLs) 

  • Transport cholesterol from liver to tissues, including artery walls, which they infiltrate, leading to the development of ATHEROMA + HEART DISEASE


  • High levels of salt: Raise blood pressure
  • High levels of saturated fat: Increase LDL levels --> higher concentration of cholesterol
  • Foods that contain antioxidents eg.vitamin C and dietary fibre REDUCE the risk of HEART DISEASE
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