Exercise capacity is associated with prognosis.S2.2-15 S2.2-17 Abnormal objective cardiac limitation to exercise is defined as an exercise maximum ventilatory equivalent of oxygen below the range expected for the specific CHD anatomic diagnosis.S2.2-18 Expected norms for CPET values should take into account age, sex, and underlying congenital diagnosis. Published studies with institution-specific norms can be used as guides, bearing in mind variability among institutional norms and ranges. Hypoxemia/hypoxia/ cyanosis See Section 3.16. for detailed definition of cyanosis. Hypoxemia is defined as oxygen saturation measured by pulse oximetry at rest 90%. Severe hypoxemia is defined as oxygen saturation at rest <85%. In patients with normal or high hemoglobin concentrations, severe hypoxemia will be associated with visible cyanosis (which requires 5 g/L desaturated hemoglobin to be appreciated). The terms cyanosis and hypoxemia (or hypoxia) are sometimes used interchangeably. Such interchangeability would not apply; however, in the presence of anemia, severe hypoxemia can be present without visible cyanosis. NYHA functional classification Class Functional Capacity I Patients with cardiac disease but resulting in no limitation of physical activity. Ordinary physical activity does not cause undue fatigue, palpitation, dyspnea, or anginal pain. II Patients with cardiac disease resulting in slight limitation of physical activity. They are comfortable at rest. Ordinary physical activity results in fatigue, palpitation, dyspnea, or anginal pain. III Patients with cardiac disease resulting in marked limitation of physical activity. They are comfortable at rest. Less than ordinary activity causes fatigue, palpitation, dyspnea, or anginal pain. IV Patients with cardiac disease resulting in inability to carry on any physical activity without discomfort. Symptoms of HF or the anginal syndrome may be present even at rest. If any physical activity is undertaken, discomfort increases. (Continued) CLINICAL STATEMENTS AND GUIDELINES of the great arteries, and TOF, amongst others. 