The heart is a muscular organ made of four chambers: two upper chambers called atria and two lower chambers called ventricles. These four chambers pump blood through the body in a rhythmic manner. The movement of blood through the body can be felt at the wrist or neck and other areas of the body and is known as the pulse. Although the heart is full of blood, it does not receive oxygen and nutrients from the blood inside the chambers, but must rely on the arteries on the surface of the heart to nourish it and keep it working properly. These surface arteries are known as the coronary arteries. There are three main coronary arteries: the right coronary artery, the left anterior descending coronary artery and the circumflex coronary artery. These arteries branch into thousands of small arteries bringing oxygen and nutrients to the heart muscle cells.

When fat and calcium build up in the inner lining of the arteries, a substance called plaque is formed. Over time the plaque buildup narrows the inside of the artery and blocks the blood trying to flow through it. This is called atherosclerosis, sometimes called "hardening of the arteries".

When atherosclerosis affects the coronary arteries, it can block the flow of blood to the heart muscle, resulting in heart pain (angina), irregular heartbeats and other problems. These can lead to a heart attack and cause damage to the heart muscle.

A major part of treating atherosclerosis and coronary artery disease includes quitting smoking, reducing high cholesterol, controlling high blood pressure and managing other factors that increase a person's risk of heart attack, stroke and other complications.