Pulmonary hypertension and pulmonary arterial hypertension: a clarification is needed

The growing interest in pulmonary hypertension (PH) in many medical specialties including cardiology, rheumatology and respiratory medicine, is possibly due to the recent availability of specific drugs approved for a group of rare conditions defined as pulmonary arterial hypertension (PAH). The terms “pulmonary hypertension” and “pulmonary arterial hypertension” appear to be quite similar, and this has led to confusion and ambiguity in both common clinical practice and the medical literature 1. It is, therefore, important to clarify the different definitions of PH, the relationship between the haemodynamic measurement and the echocardiographic estimate, and the additional diagnostic methods required for the final clinical diagnosis. In addition, it is relevant to highlight the significant role of right heart catheterisation in the diagnostic algorithm of a patient with PH. PH cannot be considered to be a specific “disease”. PH has been defined as an increase in mean pulmonary arterial pressure ( P pa) ≥25 mmHg at rest, as assessed by right heart catheterisation 2–5. Recent re-evaluation of the available data has shown that the normal P pa±sd at rest is 14±3 mmHg with an upper limit of normal of ∼20 mmHg 6, 7. The significance of P pa 21–24 mmHg is unclear. Patients presenting with P pa in this range need further evaluation in epidemiological studies. The definition of PH on exercise as a P pa >30 mmHg, as assessed by right heart catheterisation, is not supported by published data and healthy individuals can reach much higher values 6, 8. Therefore, no definition for PH on exercise as assessed by right heart catheterisation can be provided at the present time. An additional, very important haemodynamic parameter that characterises the definitions of PH is pulmonary capillary wedge pressure ( P pcw). In fact, according to various …