Coronary artery disease, also called coronary heart disease, is a heart disease. ("Coronary" means "the blood vessels of the heart".) Coronary heart disease causes plaque to build up inside the coronary arteries. This causes the coronary arteries to become narrower. An artery is a blood vessel - a tube that carries blood. After the heart supplies blood that is full of oxygen and nutrients, the arteries carry the blood to different parts of the body. The coronary arteries are very important: they supply blood to the heart muscle. So when the coronary arteries become narrower, less blood gets to the heart muscle.