Riociguat als Ersatz der Therapie mit PDE-5 Hemmern im Vergleich zu fortgesetzter Therapie mit PDE-5 Hemmern.

Drug: Adempas (Riociguat, BAY63-2521);Drug: Sildenafil;Drug: Tadalafil

Inclusion Criteria:

- Male and female patients aged 18 to 75 years.

- Patients with symptomatic PAH with a pulmonary vascular resistance (PVR) > 400
dyn*sec*cm-5, mean pulmonary artery pressure = 25 mmHg, and pulmonary capillary wedge
pressure (PCWP) = 15 mmHg as assessed by the most recent right heart catheterization
(RHC) from medical history prior to screening to confirm the diagnosis. Alternatively,
PCWP can be replaced by left ventricular end-diastolic pressure (= 15 mmHg). PAH of
the following types:

- Idiopathic

- Hereditary

- Drug and toxin induced PAH

- Associated with PAH due to:

- Connective tissue disease (CTD)

- Congenital heart disease, but only if the patient underwent surgical repair
more than one year before enrolment

- Portal hypertension with liver cirrhosis (Note: patients with clinical
relevant hepatic dysfunction are excluded; see exclusions related to
disorders in organ function)

- Patients who are on stable doses of a PDE-5i and ERA combination therapy or on stable
PDE-5i monotherapy 6 weeks prior to and at randomization but not at treatment goal
(tadalafil 20 to 40 mg once daily or sildenafil at least 60 mg daily dose).

- WHO FC III at screening and at randomization.

- 6MWD test between 165 m and 440 m at screening and at randomization.

- Stable dose of diuretics, if used, for at least 30 days prior to and at randomization.

- Patients who are able to understand and follow instructions and who are able to
participate in the study for the entire study.

- Women of childbearing potential must agree to use adequate contraception when sexually
active. Adequate contraception is defined as any combination of at least 2 effective
methods of birth control, of which at least 1 is a physical barrier (e.g. condom with
hormonal contraception like implants or combined oral contraceptives, condom with
intrauterine devices). This applies beginning with signing of the informed consent
form until 30 (+5) days after the last administration of study drug.

- Patients must have given their written informed consent to participate in the study
after having received adequate previous information and prior to any study-specific
procedures.

Exclusion Criteria:

- Participation in another interventional clinical study within 30 days prior to
screening.

- All types of PH (including PH-IIP) except subtypes of Dana Point Group I specified in
the inclusion criteria.

- Previous treatment with riociguat.

- Pregnant women (i.e., positive serum ß-human-chorionic-gonadotropin test or other
signs of pregnancy), or breast feeding women, or women with childbearing potential not
using a combination of 2 effective contraception methods (as laid out in inclusion
criterion) throughout the study.

- Patients with a medical disorder, condition, or history of such that would impair the
patient's ability to participate or complete this study, in the opinion of the
investigator.

- Relevant obstructive and restrictive or other lung diseases.

- Patients with underlying medical disorders with an anticipated life expectancy below 2
years (e.g., active cancer disease with localized and/or metastasized tumor mass).

- Cardiovascular exclusion criteria like left ventricular disease, coronary heart
disease or stroke within previous 3 months.

- Patients with hypersensitivity to the investigational drug or any of the excipients.

- Patients unable to perform a valid 6MWD test (e.g., orthopedic disease, peripheral
artery occlusive disease, which affects the patient's ability to walk). Note:
Patients, who require walking aids, may be included if in the opinion of the
investigator the walking distance is not impaired. Patients with a variance of more
than 15% between the screening and the randomization (i.e., baseline) 6MWD test.