Coronary artery disease is the most common form of heart disease. It occurs when one or more of the arteries that bring blood to the heart become narrowed or blocked by plaque, a sticky substance that can build up over time due to diet, age, or genetics. This process is called atherosclerosis, or sometimes “hardening of the arteries.” For some people, the first sign that they have coronary artery disease is a heart attack, which happens when a blockage reduces or stops blood flow to the heart, starving part of the heart muscle of oxygen. This causes damage to the heart muscle or even death. Coronary artery bypass graft (CABG) surgery is used to treat coronary artery disease.