Introduction and classification

Pulmonary hypertension (PH) encompasses a group of diseases associated with an elevated mean pulmonary artery pressure (mPAP) ≥25 mm Hg at rest. The symptoms of PH are non-specific, and it should be suspected in any patient with unexplained exertional dyspnoea, exertional dizziness (near syncope), syncopal episodes and/or signs of right ventricular dysfunction. PH can predominantly affect the precapillary part of the pulmonary circulation, for example, pulmonary arterial hypertension (PAH) or postcapillary—pulmonary venous circulation due to left heart disease (PH-LHD). A pulmonary artery wedge pressure (PAWP) or left ventricular end diastolic pressure (LVEDP) ≤15 mm Hg differentiates precapillary from postcapillary PH. The causes of PH are classified into five major groups based on similarities in pathophysiological mechanisms, clinical presentation and therapeutic options: Group 1 PAH, which can be idiopathic (IPAH), heritable (HPAH), drug-induced and toxin-induced or associated with other medical conditions, for example, systemic sclerosis, portal hypertension, congenital heart disease (CHD) and HIV infection; group 2 PH-LHD; group 3 PH due to lung disease and/or hypoxia (PH-lung); group 4 chronic thromboembolic PH (CTEPH); and group 5 PH with unclear and/or multifactorial mechanisms (box 1).1 This review article covers the investigation of a patient with suspected PH and, if the diagnosis is confirmed, the ongoing management of the patient. There will be particular emphasis on the management of patients with PAH and CTEPH because these patients may benefit from specific therapies.