| I | No limitations of physical activity. Ordinary physical activity does not cause undue fatigue, palpitation, or dyspnoea |
| II | Slight limitation of physical activity. Patients are comfortable at rest. Ordinary physical activity results in fatigue, palpitation, breathlessness, or angina pectoris |
| III | Marked limitation of physical activity. Although patients are comfortable at rest, less than ordinary activity will lead to symptoms |
| IV | Inability to carry out any physical activity without discomfort. Symptoms of congestive cardiac failure are present even at rest. Increased discomfort with any physical activity |