Coronary artery disease (CAD) is the most common form of heart disease. It is a condition that occurs when the coronary arteries that supply oxygen-rich blood and nutrients to the heart muscles become narrowed or blocked by a gradual build-up of “plaque”. Plaque is made up of fatty deposits (cholesterol), white blood cells, calcium, and other substances that collect over time in the wall of a coronary artery. As the plaque narrows the opening (lumen) of a coronary artery, it makes it difficult for adequate quantity of blood to flow to the heart muscle. This process of plaque formation and narrowing of the vessel diameter is called “atherosclerosis.” Reduction of blood flow to the heart muscle can cause chest pain (angina), shortness of breath, sweating, and pain down the arms (most commonly the left arm). Narrowing of a heart's blood vessel can result in its complete blockage and can progress gradually or can occur suddenly resulting in a heart attack, known as a myocardial infarction.