The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Chapter 3, The Heart and Aorta, is used to rate impairment in patients with coronary disease. Note that the four “functional classes” of the New York Heart Association, which are discussed in the chapter, should not be confused with the four classes used to rate impairment due to coronary heart disease. Treadmill testing of maximal exercise ability is a traditional measurement to help the evaluator place an individual in an impairment rating class. Class 1 impairment rarely is used in rating workers’ compensation impairment, and the presence of small (asymptomatic) coronary artery blockages that may progress is the justification for considering these individuals impaired even in the absence of symptoms. Classes 2, 3, and 4 describe the impairment of individuals with objectively documented symptomatic coronary disease. Class 2 impairment describes individuals who have no symptoms or who manage them with diet or medication and can achieve 90% of predicted maximal heart rate during exercise testing without specific signs of ischemia. Class 3 impairment describes individuals who have symptoms of congestive failure or angina with moderately heavy activity, and Class 4 includes individuals who have symptoms during ordinary activity. To give guidance in this process, a series of clinical examples follows the description of each class.