Secondary pulmonary hypertension

Most cases of pulmonary arterial hypertension (PAH) are not idiopathic, but rather are attributable to other disorders. This fact has become increasingly apparent following the recent establishment of centralised PAH registries in several countries. Yet, this “secondary” PAH has been the subject of even less research than idiopathic PAH, itself an orphan disease par excellence. Secondary PAH is heterogeneous: prognosis and response to vasodilator therapy differs substantially between various forms of secondary PAH, partly as a function of underlying pathophysiology, and cannot simply be extrapolated from data derived from idiopathic PAH.This article reviews the commonest secondary causes of PAH, focusing on epidemiology, risk factors, clinical presentation, treatment options, prognosis, and the role of screening. PAH secondary to chronic hypoxia, congenital heart disease, connective tissue disorders, liver disease, appetite suppressants and stimulants, and HIV infection are all considered. Strengths and limitations of available screening tests for PAH are discussed.