New or worsening chest discomfort is the most common symptom of coronary artery disease (CAD), which is plaque build-up in the arteries that supply the heart muscle with blood. Chest pain is one of the most common reasons for emergency department (ED) visits, with an estimated 8 million new cases every year. Evaluation of chest pain is expensive and time consuming, even though 75% of the time it is not due to CAD. It is necessary to carefully define the amount of CAD, even if initial tests reveal no heart attack, because this symptom may progress to heart attack and death if missed.