The majority of cases are due to there being some narrowing in the blood vessels supplying the heart. This is usually due to the presence of some atheroma within the lining of the artery. Atheroma is like fatty patches or plaques that develop within the inside lining of arteries. (This is similar to water pipes that get furred up.)
Various other uncommon conditions can also block a coronary artery.
Inflammation of the coronary arteries (rare).
A blood clot forming elsewhere in the body (for example, in a heart chamber) and travelling to a coronary artery where it gets stuck.
Complications from heart surgery.
A stab wound to the heart.
Taking cocaine, which can cause a coronary artery to go into spasm.
Some other rare heart problems.
What causes acute coronary syndrome?
Acute coronary syndrome happens because blood flow has slowed or stopped in the arteries that supply blood to the heart. Acute coronary syndrome is typically caused by coronary artery disease. Coronary artery disease, also called heart disease, is caused by atherosclerosis, or hardening of the arteries.