A Study to Evaluate Efficacy and Safety of Oral BAY63-2521 in Patients With CTEPH.

6-minute walking distance (6MWD) is a measure for the objective evaluation of a participant's functional exercise capacity.

The pulmonary vascular resistance (PVR) is a calculated hemodynamic parameter. PVR is derived from the directly measured parameters mean pulmonary arterial pressure (PAPmean) and pulmonary capillary wedge pressure (PCWP), divided by the cardiac output (CO). PVR and PAPmean are acquired during a right heart catheterization. CO is a calculated hemodynamic parameter, too. Formula: PVR = 80*(PAPmean - PCWP)/CO

N-terminal pro-brain natriuretic peptide (NT-proBNP) levels in the blood are used for screening, diagnosis of acute congestive heart failure (CHF) and may be useful to establish prognosis in heart failure.

The WHO functional assessment of pulmonary arterial hypertension ranged from functional class I (Patients with PH but without resulting limitation of physical activity) to class IV (Patients with PH with inability to carry out any physical activity without symptoms. These patients manifest signs of right-heart failure.). Changes to a lower WHO functional class resemble improvement; changes to a higher functional class resemble deterioration of PAH.

The combined endpoint "time to clinical worsening", made up of the following components, defined by the first occurrence: all-cause mortality; heart/lung transplantation; rescue endarterectomy; first hospitalization due to pulmonary hypertension; start of a new pulmonary hypertension treatment; persistent worsening of 6MWD or WHO functional class due to deterioration of PH.

The Borg CR10 Scale is a participant reported outcome measure used in clinical diagnosis of e.g. breathlessness and dyspnea. It documents the participant's exertion during a physical test. Low values indicate low levels of exertion; high values indicate more intense exertion reported by the participant. The score ranges from 0 ("Nothing at all") to 10 ("Extremely strong - Maximal").

EQ-5D utility score is a Quality-of-Life participant reported outcome measure. The utility score is calculated based on five questions concerning problems with mobility, self-care, usual activities, pain/discomfort and anxiety/depression. An increase in the utility score represents an improvement in quality of life. The score ranges from -0.594 (worst answer in all five questions) to 1 (best answer in all five questions).

The self-reported Living with Pulmonary Hypertension (LPH) questionnaire is designed to measure the effects of PH and PH-specific treatments on an individual's quality of life. The LPH total score can range from 0 (best) to 105 (worst).

All cause mortality (including cardiovascular mortality) was one component of the composite endpoint "time to clinical worsening".

Mean pulmonary arterial pressure (PAPmean) is a directly measured hemodynamic parameter. PAPmean is recorded during a right heart catheterization.

The cardiac index (CI) is a calculated hemodynamic parameter. CI is derived from the directly measured parameters cardiac output (CO), divided by the body surface area (BSA). BSA is a calculated parameter, using the subject's height and weight in the DuBois formula. Formula: BSA = (W [kg]*0.425)*(H [cm]*0.725)*0.007184 (m^2)

Systolic systemic arterial blood pressure (SBP) is a directly non-invasively measured hemodynamic parameter. Range allowed in this study at Visit 0 and/or Visit 1 before randomization: 95 - 180 mmHg.

Diastolic systemic arterial blood pressure (DBP) is a directly non-invasively measured hemodynamic parameter. Range allowed in this study at Visit 0 and/or Visit 1 before randomization: <= 110 mmHg.

Heart rate (HR) is a directly non-invasively measured hemodynamic parameter. Range allowed in this study at Visit 0 and/or Visit 1 before randomization: 50 -105 beats per minute (bpm) at rest.

Alanine Aminotransferase (ALT) is a standard clinical chemistry parameter. Normal range: 0 to 45 U/L.

Aspartate Aminotransferase (AST) is a standard clinical chemistry parameter. Normal range: 0 to 41 U/L.

Alkaline phosphatase (AP) is a standard clinical chemistry parameter. Normal range: 40 to 129 U/L (males), 35 to 104 U/L (females)

Bilirubin is a standard clinical chemistry parameter. Normal range: 0.1 to 1.2 mg/dL

Creatinine is a standard clinical chemistry parameter. Normal range: 0.25 to 1.20 mg/dL (males), 0.46 to 1.00 mg/dL (females)

Creatinine clearance is a standard clinical chemistry parameter. Normal range: 90 to 140 mL/min (males), 80 to 125 mL/min (females)

Creatine Kinase is a standard clinical chemistry parameter. Normal range: 35 to 232 U/L (males), 26 to 145 U/L (females)

Erythrocytes (red blood cells, RBC) is a standard clinical hematology parameter. Normal range: 4.6 to 5.8*10^12 cells/L (males), 4.1 to 5.2*10^12 cells/L (females)

Leukocytes (white blood cells, WBC) is a standard clinical hematology parameter. Normal range: 4.0 to 10.7*10^9 cells/L

Total lymphocytes is a standard clinical hematology parameter. Normal range: 1.0 to 4.0*10^9 cells/L

Neutrophils is a standard clinical hematology parameter. Normal range: 1.6 to 7.4*10^9 cells/L

Hemoglobin is a standard clinical hematology parameter. Normal range: 13.5 to 17.5 g/dL (males), 12.0 to 16.0 g/dL (females)

Hematocrit is a standard clinical hematology parameter. Normal range: 40 to 52% (males), 36 to 46% (females)

Potassium is a standard clinical chemistry parameter. Normal range: 3.5 to 5.3 mmol/L

Urate is a standard clinical chemistry parameter. Normal range: 4.0 to 8.5 mg/dL (males, 16-59 years), 3.4 to 8.7 mg/dL (males, >60 years) 2.5 to 7.5 mg/dL (females)

Urea (blood urea nitrogen, BUN) is a standard clinical chemistry parameter. Normal range: 4 to 25 mg/dL

Cystatin C is a biomarker. Normal range: 0.53 to 1.01 ng/mL

Triacylglycerol lipase is a standard clinical chemistry parameter. Normal range: 7 to 60 U/L

Arterial partial pressure of carbon dioxide (PaCO2) is performed as part of the capillary or arterial blood gas analysis. If possible, no supplementary oxygen was given during the resting period and while blood samples were drawn.

Arterial partial pressure of oxygen (PaO2) is performed as part of the capillary or arterial blood gas analysis. If possible, no supplementary oxygen was given during the resting period and while blood samples were drawn.

Oxygen saturation (SaO2) is measured as part of the capillary or arterial blood gas analysis. Normal blood oxygen saturation is considered 95-100 percent. If possible, no supplementary oxygen was given during the resting period and while blood samples were drawn.

PR duration was evaluated as part of the 12-lead electrocardiogram. electrocardiograms (ECGs) were recorded after the participant had been at rest for 15 minutes in a supine position.

QRS duration was evaluated as part of the 12-lead electrocardiogram. ECGs were recorded after the participant had been at rest for 15 minutes in a supine position.

QT duration was evaluated as part of the 12-lead electrocardiogram. ECGs were recorded after the participant had been at rest for 15 minutes in a supine position.

Bazett-corrected QTcB duration was evaluated as part of the 12-lead electrocardiogram. ECGs were recorded after the participant had been at rest for 15 minutes in a supine position.

Fridericia-corrected QTcF duration was evaluated as part of the 12-lead electrocardiogram. ECGs were recorded after the participant had been at rest for 15 minutes in a supine position.

RR duration was evaluated as part of the 12-lead electrocardiogram. ECGs were recorded after the participant had been at rest for 15 minutes in a supine position.

Ventricular rate was evaluated as part of the 12-lead electrocardiogram. ECGs were recorded after the participant had been at rest for 15 minutes in a supine position