To Assess The Efficacy and Safety Of Oral Sildenafil in the Treatment of Pulmonary Arterial Hypertension.

Change From Baseline in Mean Pulmonary Arterial Pressure (mPAP) at Week 12

mPAP was measured using a pressure transducer positioned at the mid-axillary line.

Time frame: Baseline and Week 12

Number of Participants With Clinical Worsening

Clinical worsening was defined as death; or lung transplantation; or hospitalization due to pulmonary hypertension; or initiation of prostacyclin therapy; or initiation of endothelin receptor antagonist therapy. (PAH=pulmonary arterial hypertension) Due to very low number of events of clinical worsening reported, the median days to clinical worsening could not be estimated.

Time frame: Baseline through Week 12

Number of Participants With Change From Baseline in PAH Criteria for Functional Capacity and Therapeutic Class at Week 12

Pulmonary arterial hypertension (PAH) Criteria for WHO Class: Class I (Participants without resulting limitation of physical activity);Class II (Participants with slight limitation of physical activity though comfortable at rest);Class III (Participants with marked limitation of physical activity,though comfortable at rest);Class IV(Participants with inability to carry out any physical activity without symptoms,manifest signs of right heart failure; dyspnoea and/or fatigue may even be present at rest; and discomfort is increased by any physical activity).

Time frame: Baseline and Week 12

Change From Baseline in B-Type Natriuretic Peptide (BNP) at Week 12