Heart surgery. Surgeons preparing a harvested artery for coronary artery bypass graft (CABG) surgery. The artery will be cleaned and tested before being grafted on to the coronary artery. Metal spreaders are being used to keep the rib cage open. During CABG a healthy artery is attached to the diseased coronary artery. This re- routes the blood flow, bypassing the blocked coronary artery. Blood vessels can become blocked by the build-up of fatty plaques, atherosclerosis. This reduces blood flow to the areas served by the vessel. Inadequate blood flow to the heart can lead to heart pain (angina) or a heart attack (myocardial infarction).