Like all other tissues and organs in the body, the heart needs a constant supply of oxygen-rich blood. If the blood supply to part of the heart is suddenly interrupted, the heart muscles may be damaged and begin to die.

If this is not treated, the affected part of the heart muscle will experience irreversible damage. If a large portion of the heart is damaged in this way, the heart will stop beating (a cardiac arrest), resulting in death.

Coronary heart disease (CHD)

Coronary heart disease (CHD) is the leading cause of heart attacks. CHD is a condition in which the coronary arteries (the major blood vessels that supply the heart with blood) get clogged up with deposits of cholesterol. These deposits are called 'plaques'.

During a heart attack, one of the plaques ruptures (bursts), causing a blood clot to develop at the site of the rupture. The clot may then block the supply of blood running through the coronary arteries to that part of the heart, triggering a heart attack.

Some people are more at risk than others of developing heart disease. Some risks you can't do anything about, including your genes, your ethnic background, your age and your gender.

But the way you live your life can also put you at risk of heart disease. You are more at risk of having a heart attack if:

• you smoke
• you have high cholesterol
• you have high blood pressure
• you have diabetes
• you are physically inactive
• you are overweight or obese
• you eat an unhealthy diet
• you have depression or are isolated from other people and don't have good support

Making lifestyle changes such as quitting smoking or making sure you do enough exercise is the most effective way to avoid having a heart attack, or having another heart attack if you have already had one.