Heart surgery. Artery (running from bottom left to centre) that has been attached to the heart in coronary artery bypass graft (CABG) surgery. Staples, or metal sutures (centre), have been used to hold the artery in place. During CABG a healthy artery, from elsewhere in the body, 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).