Table 2.

Functional classification of pulmonary hypertension according to World Health Organization (WHO).

CLASS I: Patients with pulmonary hypertension but without resulting limitation of physical activity. Ordinary physical activity does not cause undue dyspnoea or fatigue, chest pain, or near syncope.
CLASS II: Patients with pulmonary hypertension 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.
CLASS III: Patients with pulmonary hypertension resulting in marked limitation of physical activity. Less than ordinary activity causes undue dyspnoea or fatigue, chest pain, or near syncope.
CLASS IV: Patients with pulmonary hypertension with 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.