Table 1

Classification of pulmonary hypertension according to the World Health Organization 1998

1. Pulmonary arterial hypertension:
 Primary pulmonary hypertension
  Sporadic
  Familial
 Related to:
  Collagen vascular disease
  Congenital systemic to pulmonary shunts
  Portal hypertension
  HIV infection
  Drugs/toxins
   Anorexigens (aminorex, fenfluramine, dexfenfluramine)
   Other
   Definite: toxic rapeseed oil
   Very likely: amphetamines, L-tryptophan
   Possible: meta-amphetamines, cocaine, chemotherapeutic agents
  Persistent pulmonary hypertension of the newborn
  Other
2. Pulmonary venous hypertension:
 Left sided atrial or ventricular heart disease
 Left sided valvar heart disease
 Pulmonary veno-occlusive disease
 Pulmonary capillary haemangiomatosis
 Other
3. Pulmonary hypertension associated with disorders of the respiratory system and/or hypoxaemia:
 Chronic obstructive lung disease
 Interstitial lung disease
 Sleep disordered breathing
 Alveolar hypoventilation disorders
 Chronic exposure to high altitude
 Neonatal lung disease
 Alveolar capillary dysplasia
 Other
4. Pulmonary hypertension caused by chronic thrombotic and/or embolic disease:
 Thromboembolic obstruction of proximal pulmonary arteries
 Obstruction of distal pulmonary arteries
  Pulmonary embolism
   Thrombus, tumour, ova/parasites, foreign material
  In situ thrombosis
  Sickle cell disease
5. Pulmonary hypertension associated with miscellaneous diseases:
 Inflammatory
  Schistosomiasis
  Sarcoidosis
  Other
 Extrinsic compression of the central pulmonary veins
  Fibrosing mediastinitis
  Adenopathy/tumours