 - Pulmonary arterial hypertension confirmed by a RHC at any time prior to start of study, with mean pulmonary artery pressure PAPmean 25 mmHg at rest, pulmonary capillary wedge pressure PCWP or left ventricular end-diastolic pressure LVEDP 15 mmHg, and pulmonary vascular resistance PVR 240 dynseccm-5 i.e., 3.0 wood unitsm2 