[Clinical classification and epidemiology of pulmonary arterial hypertension]

Pulmonary arterial hypertension (PAH) is a rare pulmonary vascular disease. PAH includes idiopathic, familial and associated forms of PAH. The minimal prevalence in the adult French general population is 15 cases per million. PAH must be separated from pulmonary hypertension due to left heart diseases, chronic lung diseases and chronic venous thrombo-embolic disease. Idiopathic PAH mostly affects people in their 4th and 5th decades, mainly females, occasionally children and the elderly are affected. Despite major improvement of pharmaceutical treatments during the last 10 years, PAH still bears a poor prognosis. Five-year survival rates are below 75% in patients under appropriate therapy. Main prognostic factors are the level of dyspnoea on exertion, the degree of exercise impairment and signs (clinical and haemodynamic) of right heart failure. When these signs of poor prognosis are persistent treatments must be optimized.