Atherosclerosis. Illustration of a coronary artery diseased with atherosclerosis. The coronary arteries supply blood to the heart, providing the cardiac 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.