Cardiovascular Disease (WJEC GCSE Biology: Combined Science)

Causes of cardiovascular disease

• Cardiovascular disease is not just one disease, but it describes any disease that affects the heart and/or blood vessels
  • An example of a type of cardiovascular disease is coronary heart disease (CHD)
• 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 cells need to constantly respire, so it is vital that it receives a constant supply of oxygen

Coronary arteries around the heart diagram

The coronary arteries supply the heart with oxygenated blood and can lead to cardiovascular disease if damaged

• In CHD, layers of fatty material called an atheroma build up inside the coronary arteries

Atheroma build up in coronary arteries diagram

Build up of an atheroma in the coronary arteries narrows the lumen

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

The difference between blood flow in a healthy artery and a CHD artery diagram

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

Risk factors of cardiovascular disease (CVD)

• There are several risk factors which will increase the chances of coronary heart disease:
• Poor diet high in fat and salt
  • A poor diet can lead to weight gain
  • 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 to the vessels
• High blood cholesterol
  • Speeds up the build-up of fatty plaques in the arteries leading to blockages
• Smoking
  • Chemicals in smoke cause an increase in plaque buildup and an increase in blood pressure
  • Carbon monoxide also reduces the oxygen carrying capacity of the red blood cells
• Genetic factors
  • Some people have a genetic code that can cause CVD, for example, some babies are born with a small hole in their septum between their atria and this can be caused by DNA
  • Or they can have an increased risk of CVD due to their DNA, but there may not be a 100% chance of it occurring 
• A lack of exercise
  • This is linked to the poor diet factor where carrying extra weight puts a strain on the heart
  • Exercise helps to lower blood pressure and blood cholesterol, which decreases the risk of CVD

Statins

• These drugs are taken daily and work by lowering blood cholesterol 
• They block an enzyme in the liver which is needed to make cholesterol
• This reduces the risk of atheroma formation

Angioplasty

• Angioplasty is a surgical procedure designed to treat people with a severe atheroma blocking an artery
• A narrow catheter (tube) is threaded through the groin up to the blocked vessel
• A tiny balloon inserted into the catheter is pushed up to the blocked vessel and then inflated
• This flattens the atheroma against the wall of the artery, clearing the blockage
• To keep the artery clear, a stent (a piece of metal / plastic mesh) is also inserted which pushes against the wall of the artery
• Sometimes the stent is coated with a drug that slowly releases medication to prevent further build-up of atheroma

The process of angioplasty diagram

Inserting a stent into a blocked artery as part of angioplasty

Changes to lifestyle/diet

• Quit smoking cigarettes 
• Reduce animal fats in the diet and eat more fruits and vegetables - this will reduce cholesterol levels in the blood and help with weight loss if overweight
• Exercise regularly, again, this will help with weight loss, decrease blood pressure and cholesterol levels and help reduce stress

Disadvantages of each treatment

• When treating CVD, each individual's circumstances must be considered when choosing the treatment
• Not all treatments suit each person due to certain disadvantages 
• Some examples of these are listed below: 

Disadvantages of CVD treatments table