Pulmonary Arterial Hypertension

The last 10 years have seen significant advances in the understanding of the pathophysiology and treatment of pulmonary arterial hypertension (PAH). This has included new insights into the genetics, cell-signalling pathways and pathological changes seen in the small pulmonary arteries as well as the introduction of new treatments which have improved prognosis. The classification of pulmonary hypertension (PH) has also been changed several times, most recently in 2003. It now divides forms of PH into 5 broad groups according to their pathophysiology and response to treatment. This review focuses primarily on the advances that have been made in the comprehension and treatment of Group 1 (PAH); however reference is also made to other groups within the classification. Pharmacologic treatment now includes calcium-channel blockers, endothelin antagonists, prostanoids, phosphodiesterase type 5 inhibitors, anticoagulants and diuretics. There are 2 recent sets of guidelines directing treatment, one published by the American College of Chest Physicians in 2007 and the most recent published by the National Pulmonary Hypertension Centres of the UK and Ireland in 2008. The recent advances in understanding of the underlying cellular mechanisms have also opened the doorway to new potential therapies such as stem cell transplantation and the targeting of platelet-derived factors and apoptosis.