Abstract： @@ 1 Introduction Idiopathic pulmonary arterial hypertension (IPAH) is a progressive, nearly fatal condition that until recently has had very few treatment options.Median survival time for untreated IPAH was 2.8 years without effective drug intervention.IPAH is characterized by deregulated proliferation of pulmonary arterial endothelial and intimal smooth muscle cells resulting in progressive pulmonary vascular remodeling and an increase in pulmonary arterial pressure.