PAH is characterized by increased pulmonary vascular resistance due to remodeling and occlusion of the pulmonary arterioles. Left untreated, PAH leads irremediably to right ventricular (RV) hypertrophy, pressure overload and dilation resulting in death within 2-3 years (11). For the past two decades, it has been appreciated that the integrity of the RV function, rather than the degree of pulmonary vascular injury, is the major determinant of symptoms and mortality in patients with PAH. RV dysfunction at time of presentation, as reflected by an elevation in right atrial pressure (RAP), the presence of pericardial effusion or depressed cardiac output (CO), is a powerful prognosticator of death (12).