Pulmonary arterial hypertension (PAH), which is defined as an elevation in pulmonary arterial pressure and pulmonary vascular resistance, is a severe hemodynamic abnormality common to a variety of diseases and syndromes. Elevation in pulmonary arterial pressure causes an increase in right ventricular afterload, impairing right ventricular function and ultimately leading to inactivity and death. The goal of PAH treatment is to lengthen survival time, to ameliorate symptoms of PAH, and to improve health related quality of life (HRQOL).