Types of pulmonary hypertension (PH) according to European Society of Cardiology (ESC)/European Respiratory Society (ERS) guidelines [23]; those associated with congenital heart defects are marked in bold
| Classification | Description |
| 1 | PAH |
| 1.1 | Idiopathic |
| 1.2 | Heritable |
| 1.2.1 | BMPR2 mutation |
| 1.2.2 | Other mutations |
| 1.3 | Drug and toxin induced |
| 1.4 | Associated with: |
| 1.4.1 | Connective tissue disease |
| 1.4.2 | HIV infection |
| 1.4.3 | Portal hypertension |
| 1.4.4 | Congenital heart disease |
| 1.4.4.1 | Eisenmenger's syndrome |
| 1.4.4.2 | PAH associated with prevalent systemic to pulmonary shunt |
| 1.4.4.3 | PAH with small/coincidental defects |
| 1.4.4.4 | PAH after defect correction |
| 1.4.5 | Schistosomiasis |
| 1ʹ | Pulmonary veno-occlusive disease and/or pulmonary capillary haemangiomatosis |
| 1ʹ.1 | Idiopathic |
| 1ʹ.2 | Heritable |
| 1ʹ.2.1 | EIF2AK4 mutation |
| 1ʹ.2.2 | Other mutations |
| 1ʹ.3 | Drug, toxin and radiation induced |
| 1ʹ.4 | Associated with: |
| 1ʹ.4.1 | Connective tissue disease |
| 1ʹ.4.2 | HIV infection |
| 1ʹʹ | Persistent PH of the newborn |
| 2 | PH due to left-heart disease |
| 2.1 | Left-ventricular systolic dysfunction |
| 2.2 | Left-ventricular diastolic dysfunction |
| 2.3 | Valvular disease, obstruction and congenital cardiomyopathy |
| 2.4 | Congenital/acquired left-heart inflow/outflow tract obstruction and congenital cardiomyopathies |
| 2.5 | Congenital/acquired pulmonary vein stenosis |
| 3 | PH due to lung disease and/or hypoxia |
| 3.1 | COPD |
| 3.2 | ILD |
| 3.3 | Other pulmonary diseases with mixed restrictive and obstructive patterns |
| 3.4 | SDB |
| 3.5 | Alveolar hypoventilation disorders |
| 3.6 | Chronic exposure to high altitude |
| 3.7 | Developmental lung diseases |
| 4 | CTEPH and other pulmonary artery obstructions |
| 4.1 | CTEPH |
| 4.2 | Other pulmonary artery obstructions |
| 4.2.1 | Angiosarcoma |
| 4.2.2 | Other intravascular tumours |
| 4.2.3 | Arteritis |
| 4.2.4 | Congenital pulmonary arterial stenoses |
| 4.2.5 | Parasites (hydatidosis) |
| 5 | PH with unclear and/or multifactorial mechanisms |
| 5.1 | Haematological disorders (chronic haemolytic anaemia, myeloproliferative disorders and splenectomy) |
| 5.2 | Systemic disorders (sarcoidosis, pulmonary histiocytosis, lymphangioleiomyomatosis and neurofibromatosis) |
| 5.3 | Metabolic disorders (glycogen storage disease, Gaucher's disease and thyroid disorders) |
| 5.4 | Others (pulmonary tumoral thrombothic microangiopathy, fibrosing mediastinitis, chronic renal failure (with/without dialysis) and segmental PH) |
PAH: pulmonary arterial hypertension; BMPR2: bone morphogenetic protein receptor type 2; EIF2AK4: eukaryotic translation initiation factor 2 alpha kinase 4; COPD: chronic obstructive pulmonary disease; ILD: interstitial lung disease; SDB: sleep disordered breathing; CTEPH: chronic thromboembolic pulmonary hypertension.