- Patients diagnosed with Pulmonary Arterial Hypertension (PAH) participating or having participated in the Bayer-sponsored studies 12935, 16719 or 18588, who have completed the main study phase and are still being treated with riociguat (either while still being on treatment with the respective study drug or by commercial means with Adempas) and who, in the opinion of the investigator, are expected to continue to have an overall positive benefit/risk from continuing treatment.