Biological Basis of Heart Disease

Coronary Heart Disease (CDH) 

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

Atheroma

- 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

Thrombosis

• 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

Aneurysm

• 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

Smoking

• 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:

 CARBON MONOXIDE: 

• 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

NICOTINE:

• Stimulates production of hormone adrenaline -> increase heart rate + raises blood pressure
• Also makes platelets in blood more 'sticky' -> higher risk of thrombosis
• Increases risk of HEART DISEASE, STROKES, MYOCARDIAL INFARCTION

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 

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

Diet

• 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