It occurs when fatty substances accumulate in the inner lining, or walls, of an artery. A patch of this is called plaque.
Plaques can affect both large and medium sized arteries.
Over time the inner lining of blood vessels can become thick and hard. A heart attack occurs when the flow of blood through an artery that leads to the heart muscle becomes blocked by plaque. If an artery carrying blood to a leg or arm becomes blocked, then numbness, pain, and even gangrene may develop. When an artery in the brain becomes blocked, a stroke results. Because plaques contain cholesterol, people with high levels of cholesterol in their blood have a greater chance of plaque formation.