Understanding the heart and coronary arteries

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The heart is mainly made of special muscle. The heart pumps blood into arteries (blood vessels) which take the blood to every part of the body.

Like any other muscle, the heart muscle needs a good blood supply. The coronary arteries take blood to the heart muscle. The main coronary arteries branch off from the aorta. (The aorta is the large artery which takes oxygen-rich blood from the heart chambers to the body.) The main coronary arteries divide into smaller branches which take blood to all parts of the heart muscle.

What happens when you have a myocardial infarction?

If you have an MI, a coronary artery or one of it's smaller branches is suddenly blocked. The part of the heart muscle supplied by this artery loses it's blood (and oxygen) supply. This part of the heart muscle is at risk of dying unless the blockage is quickly undone. (The word 'infarction' means death of some tissue due to a blocked artery which stops blood from getting past.)

If one of the main coronary arteries is blocked, a large part of the heart muscle is affected. If a smaller branch artery is blocked, a smaller amount of heart muscle is affected. In people who survive an MI, the part of the heart muscle that dies ('infarcts') is replaced by scar tissue over the next few weeks.