Hypertension, Pulmonary

Inclusion Criteria

- Patients with pulmonary hypertension stable for the last 6 weeks
 - Treated with Sildenafil 3 × 20 mg
 - Undergoing routine invasive diagnostics.

Exclusion Criteria

- Pre-existing lung disease other than pulmonary arterial hypertension, 
 - Acute or severe chronic left heart failure, 
 - Severe coronary artery disease, 
 - Uncontrolled arterial hypertension; 
 - Congenital or acquired valvular or myocardial disease except acquired tricuspid valve insufficiency due to pulmonary hypertension, 
 - Systolic blood pressure < 100 mmHg, heart rate < 55 bpm or >105 bpm, PaO2/FiO2 < 50 mmHg, 
 - PaCO2 > 55 mmHg, 
 - Severe hepatic insufficiency, 
 - Severe renal insufficiency, 
 - Administration of strong CYP3A4 inhibitors or inductors