MODEL RELEASED. Heart bypass surgery. Surgeon sewing up a patient's leg after removing an artery from it for use in a coronary artery bypass graft (CABG). 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, known as 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).