Table 1 Causes of pulmonary hypertension

1. Pulmonary arterial hypertension

This category is broken down further into several subcategories. These categories include: idiopathic, heritable and drug/toxin induced. There is also a category for pulmonary arterial hypertension secondary to certain diseases, including congenital heart disease, connective tissue diseases, HIV infection, portal hypertension and schistosomiasis. Group 1′ includes pulmonary veno-occlusive disease (PVOD) and/or pulmonary capillary haemangiomatosis. Group 1″ is persistent pulmonary hypertension of the newborn.

2. Pulmonary hypertension secondary to left heart disease

This category may be caused due to left-heart disease of the valves, systolic dysfunction or diastolic dysfunction. The Nice classification added congenital/acquired left heart inflow/outflow tract obstruction along with congenital cardiomyopathies to this category.

3. Pulmonary hypertension with lung disease/hypoxaemia

This category may be caused by COPD, interstitial lung diseases, pulmonary diseases with a mixed restrictive and obstructive pattern, sleep-disordered breathing, alveolar hypoventilation disorders, chronic exposure to high altitude and developmental lung diseases.

4. Chronic thromboembolic pulmonary hypertension

This category arises in patients who have had chronic thromboembolic disease resulting in reorganisation of the pulmonary vasculature.

5. Pulmonary hypertension with unclear multifactorial mechanism

This is a broad category that includes pulmonary hypertension secondary to haematological disorders (including chronic haemolytic anaemia), systemic disorders (like sarcoidosis and lymphangioleiomyomatosis), metabolic disorders (like glycogen storage diseases or thyroid disorders) and other causes (including chronic renal failure and segmental pulmonary hypertension).