1. Department of Thoracic and Cardiovascular Surgery, West German Heart and Vascular Center, University of Duisburg-Essen, Essen, Germany
2. Department of Medicine, Faculty of Medicine, Imperial College London, London, UK
3. Department of Anesthesiology and Intensive Care Medicine, University Hospital of Cologne, Cologne, Germany
4. Department of Cardiology & Vascular Medicine, West German Heart and Vascular Center, University of Duisburg-Essen, Essen, Germany