Heart attacks are caused by the blood supply to the heart being 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) become clogged with deposits of cholesterol. These deposits are called plaques.
Before a heart attack, one of the plaques ruptures (bursts), causing a blood clot to form 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:
- a high-fat diet
- high cholesterol
- high blood pressure (hypertension)
- being overweight or obese
Find out more about the causes of CHD.
Less common causes
Some less common causes are described here.
Using stimulants such as cocaine, amphetamines (speed) and methamphetamines (crystal meth) can cause coronary arteries to narrow, restricting blood supply and triggering a heart attack.
Heart attack from the use of cocaine is 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.
Page last reviewed: 28 November 2019
Next review due: 28 November 2022