Table 1 Clinical classification of pulmonary hypertension

1. Pulmonary arterial hypertension (PAH)

1.1. Idiopathic (IPAH)

1.2. Familial (FPAH)

1.3. Associated with (APAH)

1.3.1. Collagen vascular disease

1.3.2. Congenital systemic-to-pulmonary shunts

1.3.3. Portal hypertension

1.3.4. HIV infection

1.3.5. Drugs and toxins

1.3.6. Other (thyroid disorders, glycogen storage disease, Gaucher disease, hereditary hemorrhagic telangiectasia, hemoglobinopathies, myeloproliferative disorders, splenectomy)

1.4. Associated with significant venous or capillary involvement

1.4.1. Pulmonary veno-occlusive disease (PVOD)

1.4.2. Pulmonary capillary hemangiomatosis (PCH)

1.5. Persistent pulmonary hypertension of the newborn

2. Pulmonary hypertension with left heart disease

2.1. Left-sided atrial or ventricular heart disease

2.2. Left-sided valvular heart disease

3. Pulmonary hypertension associated with lung diseases and/or hypoxemia

3.1. Chronic obstructive pulmonary disease

3.2. Interstitial lung disease

3.3. Sleep-disordered breathing

3.4. Alveolar hypoventilation disorders

3.5. Chronic exposure to high altitude

3.6. Developmental abnormalities

4. Pulmonary hypertension owing to chronic thrombotic and/or embolic disease

4.1. Thromboembolic obstruction of proximal pulmonary arteries

4.2. Thromboembolic obstruction of distal pulmonary arteries

4.3. Nonthrombotic pulmonary embolism (tumor, parasites, foreign material)

5. Miscellaneous: sarcoidosis, histiocytosis X, lymphangiomatosis, compression of pulmonary vessels (adenopathy, tumor, fibrosing mediastinitis)