Coronary artery disease is the most common type of heart disease and the leading cause of death worldwide. It occurs when the arteries that supply blood to the heart become narrowed or blocked by a buildup of "plaque" - cholesterol or other fatty deposits that build on the inner wall of the artery. Over time, this plaque build up results in a reduction of blood flow to the heart, which can cause chest pain. If the artery becomes completely blocked, usually by a blood clot, oxygen is prevented from reaching the heart which can result in a heart attack and/or damage to the heart tissue.