Heart attacks are causedby the blood supply to the heartbeing suddenly interrupted. Without this supply, heart muscles may be damaged and begin to die.

Without treatment,the heart muscles will experience irreversible damage.

If a large portion of the heart is damaged in this way, the heart stops beating (known as a cardiac arrest), resulting in death.

Coronary heart disease

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.

Before a heart attack, one of the plaques ruptures (bursts), causing a blood clot to develop at the site of the rupture. The clot may block the supply of blood to the heart, triggering a heart attack.

Your risk of developing CHD is increased by:

  • smoking
  • a high-fat diet
  • diabetes
  • high cholesterol
  • high blood pressure
  • being overweight or obese

Read about the causes of CHD .

Less common causes

Some less common causes are described below.

Drug misuse

Stimulants such as cocaine, amphetamines (speed) and methamphetamines(crystal meth) can causecoronary arteries to narrow, restricting blood supply and triggering a heart attack.

Heart attacksfrom the use of cocaine are one of the most common causes of sudden death in young people.

Lack of oxygen in the blood (hypoxia)

If levels of oxygen in the blood decrease due to carbon monoxide poisoning or a loss of normal lung function, the heart will receive un-oxygenated blood.

This will result in the heart muscles being damaged, triggering a heart attack.



Angina is chest pain caused by a reduced flow of blood to the heart, typically resulting from heart disease.


Arteries are blood vessels that carry blood from the heart to the rest of the body.


Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.


Cholesterol is a fatty substance made by the body found in blood and tissue. It is used to make bile acid, hormones and vitamin D.


The heart is a muscular organ that pumps blood around the body.

Heart attack,

A heart attack happens when there is a blockage in one of the arteries in the heart.

Heart bypass

A heart (coronary) bypass is surgery to redirect the flow of blood around a clogged artery, by creating a new pathway for blood to travel in.

High blood pressure

Hypertension is when the pressure of the blood in your bloodstream is regularly above 140/90 mmHG.


Obesity is when a person has an abnormally high amount of body fat.

Content supplied by the NHS Website

Medically Reviewed by a doctor on 16 Nov 2016