Coronary artery disease (CAD) is a disease affecting the arteries that surround the heart and supply blood to the heart muscle. When the heart muscle does not receive enought blood flow to meet its need, pain or pressure in the chest, arm, or jaw (angina pectoris) can result. this is a warning sign that your heart is having difficulty, and, if left untreated, can eventually result in a heart attack (myocardial infarction).