The heart is the primary organ of the cardiovascular system. It is a beating muscle that continually pumps blood to the rest of the body. The coronary arteries supply the heart itself with the necessary oxygen and nutrients it needs to function effectively. In a healthy person, the walls of the artery are smooth and uniform in thickness. Over time, however, a high level of circulating cholesterol can cause fatty deposits, called plaque, to accumulate. If blockage of a coronary artery exceeds 70 percent, the risk is increased for experiencing a heart attack; the risk is almost certain when plaque completely blocks a coronary artery.
