World Health Organization classification of functional status of patients with pulmonary hypertension
| Class | Descriptiona |
| WHO-FC I | Patients with PH but without resulting limitation of physical activity. Ordinary physical activity does not cause undue dyspnoea or fatigue, chest pain, or near syncope. |
| WHO-FC II | Patients with PH resulting in slight limitation of physical activity. They are comfortable at rest. Ordinary physical activity causes undue dyspnoea or fatigue, chest pain, or near syncope. |
| WHO-FC III | Patients with PH resulting in marked limitation of physical activity. They are comfortable at rest. Less than ordinary activity causes undue dyspnoea or fatigue, chest pain, or near syncope. |
| WHO-FC IV | Patients with PH with an inability to carry out any physical activity without symptoms. These patients manifest signs of right heart failure. Dyspnoea and/or fatigue may even be present at rest. Discomfort is increased by any physical activity. |
PH, pulmonary hypertension; WHO-FC, World Health Organization functional class. aFunctional classification of PH modified after the New York Heart Association functional classification according to the World Health Organization 1998 [147].