In this situation the lining of an atheromatous plaque ruptures. As a result the blood in the artery comes into contact with the fatty material of the plaque. Just as when you cut yourself the blood clots on contact with the air so on contact with the fatty material it clots. This clot can block the flow of blood in the artery. As a result the portion of heart muscle supplied by the artery is staved of its oxygen supply. This results in the (usually) severe and persistent chest pain of a heart attack. Unless the supply of blood is rapidly restored some of the heart muscle will die. The quicker the supply is restored the less the damage that results.

Until recently the main treatment of heart attacks was the administration of clot busting drugs such as streptokinase through a vein. Increasingly patients are being taken immediately to a specialist hospital for immediate angioplasty.