Pulmonary hypertension is characterized by an increase in the pressures in the blood supply to the lungs greater than a mean pressure of 25mmHg and a concomitant increase in overall pulmonary vascular resistance (PVR). In patients who have remodeling of their pulmonary vasculature, PVR will increase with exercise instead of decreasing as it would in normal patients. Based on published evidence, the investigators intend to investigate the effects of inhaled nitric oxide (iNO) on patients undergoing standard exercise techniques who have separately and previously had an implanted pulmonary artery monitoring device (CardioMems by St Jude Medical, Inc.) placed.