| Class I | No limitation of physical activityactivity and symptoms with ordinary activity | 20% mortality at 5 years |
| Class II | Slight limitation in physical activity and symptoms with ordinary activity | 3-25% mortality per year |
| Class III | Marked limitation of physical activity and symptoms with less than ordinary activity | 10-45% mortality per year |
| Class IV | Inability to carry out any physical activity without discomfort and symptoms at rest | 40-50% mortality at 1 year |