Context and Definition

Pulmonary hypertension (PH) is an elevation in pulmonary vascular pressure that can be caused by an isolated increase in pulmonary arterial pressure or by increases in both pulmonary arterial and pulmonary venous pressures [1]. The World Health Organization (WHO) diagnostic classification of PH has 5 classes based on pathophysiology and aetiology.

Pulmonary arterial hypertension (PAH) is the most widely studied class of PH. It refers to conditions that share common isolated elevations in pulmonary arterial pressure, namely: sporadic PAH, familial PAH and PAH associated with other diseases (e.g. collagen vascular disease and congenital systemic-to-pulmonary shunts), PAH associated with drugs and toxins (e.g. appetite suppressants such as fenfluramine, cocaine and amphetamines).

PAH is haemodynamically defined as a resting mean pulmonary arterial pressure greater than 20 Hg with a normal pulmonary capillary or left atrial pressure (<15 mm Hg) [1-3]. The revised definition incorporates inclusion of pulmonary vascular resistance (PVR) ≥3 Wood units (WU) in the definition of all forms of pre-capillary PH.

PH is suggested when an echocardiogram-derived estimate of pulmonary arterial systolic pressure exceeds 40 mm Hg at rest.