1. University Hospital of Zurich, Department of Pneumonology, C HOER 4, Rämistrasse 100, 8091 Zurich, Switzerland
2. National Pulmonary Hypertension Service, Imperial College Healthcare NHS Trust, Hammersmith Hospital, London, W12 0HS, UK
3. Amsterdam UMC, De Boelelaan 1117, 1081 HV Amsterdam, the Netherlands
4. National Heart & Lung Institute, Imperial College London, Cale Street, London, SW3 6LY, UK