How your heart works

Your heart is a muscle that pumps blood to all parts of your body. The blood gives your body the oxygen and nourishment it needs to work properly.

  • The heart has two sides separated by a muscular wall.
  • The heart has two sides – left and right, separated by a muscular wall.
  • There is an upper and lower chamber on each side connected by valves that direct the flow of blood.
  • The smaller upper chambers are known as the atria and the larger lower chambers are the ventricles.
  • The pumping of the heart is controlled by special fibres that conduct electrical signals to the various chambers.
  • The right side of the heart pumps the blood to the lungs, where it receives oxygen.
  • Blood enters the left side of the heart from the lungs and the heart pumps the oxygen-rich blood around the body.

Coronary arteries

Coronary arteries supply the heart muscle with blood. The left and right coronary arteries divide many times to spread over the heart muscle wall and give it blood and oxygen. The coronary arteries get blood from the aorta, the major artery taking blood to the rest of the body.

Coronary heart disease

Coronary heart disease affects many people. It’s a chronic condition – that means it is long term.
Coronary heart disease happens when fatty material builds up in your arteries. This makes them narrower. The fatty material is called ‘plaque’. Plaque builds up slowly, and this process is called atherosclerosis. It can start when you are young and be well advanced by middle age.
Stable plaque is generally not harmful but if the arteries narrow too much it can cause angina.
Unstable plaque has more fat, a thin cap and is inflamed. It does not have to be associated with severe narrowing of the artery. Unstable plaque can develop a crack on the surface, exposing the contents of the plaque to the blood. Blood cells try to seal the gap in the surface with a blood clot. The blood clot partially or completely blocks the artery.
If your arteries become too narrow, less blood can reach your heart muscle. This may lead to symptoms such as angina.
If a blood clot forms in a narrow artery and blocks the blood supply to part of your heart, it can cause a heart attack. While atherosclerosis (a hardening and narrowing of the arteries) develops slowly over decades, the major consequences can appear to be sudden.
Some people may not know they have coronary heart disease until they have a heart attack.