The heart is a muscular pump. Like all muscles, the heart needs oxygen to carry out aerobic respiration which releases the energy for it to contract. The coronary arteries supply blood and therefore oxygen, to the heart muscle.
The coronary arteries may become blocked by a build-up of fatty material, caused by certain kinds of 'bad' cholesterol. As the fatty material increases, one or more coronary arteries narrow and can become blocked.
If a blockage builds up, blood clots can form, totally blocking the artery. The amount of oxygen reaching the heart muscle is reduced. A person will develop chest pain and if left untreated, a heart attack can occur resulting in damage to, or death of, the heart muscle. Part of the heart muscle, or the whole heart, will die.