Atherosclerosis. Illustration of branches of a coronary artery on the surface of the heart, in which one branch is diseased with atherosclerosis. Cardiac muscle of the heart is seen below. The coronary arteries supply blood to the heart, feeding this muscle with oxygen. Here, an arterial branch is cut through to reveal build-up of atheroma (yellow), a fatty plaque that develops on the inner arterial wall. Both ballooning and narrowing of the artery can result. The disease of atherosclerosis causes irregular blood flow which can result in clot formation (thrombosis) or stenosis (blockage). Heart attack occurs when the heart muscle is starved of blood and oxygen.