TABLE 2 Updated clinical classification of pulmonary hypertension (PH)
 1.1 Idiopathic PAH
 1.2 Heritable PAH
 1.3 Drug- and toxin-induced PAH (table 3)
 1.4 PAH associated with:
  1.4.1 Connective tissue disease
  1.4.2 HIV infection
  1.4.3 Portal hypertension
  1.4.4 Congenital heart disease
  1.4.5 Schistosomiasis
 1.5 PAH long-term responders to calcium channel blockers (table 4)
 1.6 PAH with overt features of venous/capillaries (PVOD/PCH) involvement (table 5)
 1.7 Persistent PH of the newborn syndrome
2 PH due to left heart disease
 2.1 PH due to heart failure with preserved LVEF
 2.2 PH due to heart failure with reduced LVEF
 2.3 Valvular heart disease
 2.4 Congenital/acquired cardiovascular conditions leading to post-capillary PH
3 PH due to lung diseases and/or hypoxia
 3.1 Obstructive lung disease
 3.2 Restrictive lung disease
 3.3 Other lung disease with mixed restrictive/obstructive pattern
 3.4 Hypoxia without lung disease
 3.5 Developmental lung disorders
4 PH due to pulmonary artery obstructions (table 6)
 4.1 Chronic thromboembolic PH
 4.2 Other pulmonary artery obstructions
5 PH with unclear and/or multifactorial mechanisms (table 7)
 5.1 Haematological disorders
 5.2 Systemic and metabolic disorders
 5.3 Others
 5.4 Complex congenital heart disease

PAH: pulmonary arterial hypertension; PVOD: pulmonary veno-occlusive disease; PCH: pulmonary capillary haemangiomatosis; LVEF: left ventricular ejection fraction.