**Abstract**

Pulmonary hypertension (PH) is a complex and multifactorial syndrome, partly unknown, characterized by a profound alteration of pulmonary vasculature and, consequentially, a rise in the pulmonary vascular load, leading to hypertrophy and remodeling of the right heart chambers. The World Health Organization assembles the several forms of PH into five clinical groups: group 1 includes pulmonary arterial hypertension, previously defined as idiopathic forms, group 2 is PH due to left-sided heart diseases, group 3 PH due to lung diseases, hypoxia, or both, group 4 due to pulmonary-artery obstruction, and group 5 PH, which includes forms with multifactorial or unclear mechanisms. In this chapter, we would like to delineate the clinical and hemodynamic definitions of PH and, for each group, we will describe the pathophysiological mechanisms, the diagnostic pathway, and the pharmacological approach and treatment. Finally, we would also like to focus on the latest trials and future therapeutic perspectives for this disease.

**Keywords:** pulmonary hypertension, pulmonary arterial hypertension, right heart failure, right heart catheterization, pulmonary circulation
