Open Label Access Study Of Sildenafil In Adult Patients With Pulmonary Arterial Hypertension Completing A1481244 Study

Inclusion Criteria: * Subject who complete the A1481244 study and require Sildenafil (Revatio TM) 20 mg TID therapy. * All women of childbearing potential must use adequate contraception throughout the study and four weeks after completion of the study Exclusion Criteria: * Pregnant or lactating women * Participation in other studies during study participation * Other severe acute or chronic medical or psychiatric condition or laboratory abnormality that may increase the risk associated with study participation