WHO functional classification of pulmonary hypertension10
| NYHA/WHO functional class | |
| Classifications | Symptoms |
| Class I | No symptoms and no limitation in ordinary physical activity. |
| Class II | Mild symptoms (mild shortness of breath and/or angina) and slight limitation during ordinary activity. |
| Class III | Marked limitation in activity due to symptoms, even during less-than-ordinary activity. Comfortable only at rest. |
| Class IV | Severe limitations. Experiences symptoms even while at rest. |