WHAT IS PH?

DEFINITION AND CLASSIFICATION

Pulmonary hypertension (PH) simply represents an elevated mean pulmonary artery pressure ≥ 25 mmHg measured at right heart catheterisation. This can be a consequence of pulmonary arterial hypertension (PAH) or other conditions such as left-sided heart disease or hypoxic lung disease.

Pulmonary arterial hypertension (PAH) is caused by a progressive increase in pulmonary vascular resistance (PVR) leading to right ventricular failure and premature death. The condition is diagnosed at right heart catheterisation by:

– sustained elevation of mean pulmonary arterial pressure to ≥25 mmHg AND.
– a mean pulmonary artery occlusion pressure of ≤15 mmHg AND.
– a pulmonary vascular resistance (PVR) >3 Wood units (WU).
in the absence of other causes of precapillary PH.

The classification of conditions leading to pulmonary hypertension is clinically based and was last defined in the ESC/ERS guidelines in 2015. The major classes are as follows:

1. Pulmonary arterial hypertension.Pulmonary arterial hypertension.
1A. Pulmonary veno-occlusive disease and/or pulmonary capillary haemangiomatosis .
1B. Persistent pulmonary hypertension of the newborn.
2. Pulmonary hypertension due to left heart disease.
3. Pulmonary hypertension due to lung diseases and/or hypoxia.
4. Chronic thromboembolic pulmonary hypertension and other pulmonary artery obstructions.
5. Pulmonary hypertension with unclear and/or multifactorial mechanisms.

Detailed ERS table is available here