1. Department of Cardiovascular Surgery, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
2. Division of Cardiovascular Surgery, University Hospital Zurich, University of Zurich, Zurich, Switzerland
3. Department of Cardiovascular Surgery, University Hospital Berne, Berne, Switzerland
4. Department of Thoracic, Cardiac and Vascular Surgery, University Hospital Tübingen, Tübingen, Germany
5. Department for Vascular and Endovascular Surgery, Klinikum rechts der Isar, Technical University Munich, Munich, Germany
6. Institute of Medical Informatics, Biometry and Epidemiology, University Clinic Essen, University Duisburg-Essen, Essen, Germany
7. Department of Cardiology, West-German Heart and Vascular Center Essen, University Hospital Essen, Essen, Germany