Coronary artery disease is caused by atherosclerosis. Atherosclerosis is the buildup of plaque inside your arteries. Plaque consists of cholesterol, fatty substances, waste products, calcium and the clot-making substance fibrin. As plaque continues to collect on your artery walls, your arteries narrow and stiffen. Plaque can clog or damage your arteries, which limits or stops blood flow to your heart muscle. If your heart does not get enough blood, it can't get the oxygen and nutrients it needs to work properly. This condition is called ischemia. Not getting enough blood supply to your heart muscle can lead to chest discomfort or chest pain (called angina). It also puts you at risk for a heart attack.