Sildenafil Therapy For Subjects Who Derive Clinical Benefit From Continued Treatment With Sildenafil

Inclusion Criteria:

• Patients Who Completed study A1481156 and Are Judged by the Investigator to Derive Clinical Benefit from Continued Treatment with Sildenafil, Prior to Reimbursement and Availability for Subjects in Russian Federation.
• Child bearing age women should have appropriate contraception.
• Signed informed consent. Patients who have a wish and possibility to follow treatment regimens in terms of the study.

Exclusion Criteria:

• Pregnant and lactating women.
• Participation in other studies in the current moment or during study period except of A1481156.
• Patients with severe acute or chronic diseases psychiatric disorders or laboratory abnormalities.