Switching of Sildenafil to Riociguat in CTEPH Patients

Oral riociguat administered according to established dose-adjustment scheme. Riociguat will be administered starting at at 1mg three times per day. If patient systolic blood pressure maintains at 95mmHg or higher, the dose will be increased 0.5mg every 2 weeks up to a maximum dose 2.5mg three times per day over 8-week period