Class I: No limitation of physical activity ordinary physical activity does not cause undue fatigue or dyspnea. Comfortable at rest, but ordinary physical activity results in fatigue or dyspnea. Class III: Marked limitation of physical activity wit out symptoms. Symptoms are present even at rest If any physical activity is undertaken, symptoms are increased. Class IV: Unable to carry on any physical activity without symptoms. Symptoms are present even at rest. If any physical activity is undertaken, symptoms are increased.