Angina pectoris occurs when the heart muscle does not receive enough oxygen to function effectively and pump blood around the body. This may be because there is too little oxygen in the bloodstream or because not enough blood is reaching the heart.

In most people, angina pectoris is caused by the large blood vessels that carry blood to the heart (coronary arteries) becoming progressively narrowed by fatty deposits (a process known as atherosclerosis).

In rare cases, angina may be caused by diseases of the heart valves, abnormal thickening of the heart muscle (hypertrophic cardiomyopathy), or uncontrolled high blood pressure (hypertension).

Angina pectoris occurs when a coronary artery almost become blocked.