1. Department of Thoracic and Cardiovascular Surgery, University of Duisburg-Essen, Essen, Germany
2. Centre for Clinical Trials Essen (ZKSE) at the Institute for Medical Informatics, Biometry and Epidemiology, University of Duisburg-Essen, Essen, Germany
3. Department of Cardiac and Vascular Surgery, University of Freiburg, Freiburg, Germany
4. Department of Cardiac and Vascular Surgery, University of Kiel, Kiel, Germany
5. Department of Neurology, University of Duisburg-Essen, Essen, Germany
6. Department of Heart, Thoracic, Transplantation and Vascular Surgery, Medical School of Hannover, Hannover, Germany
7. Department of Cardiac Surgery, University of Leipzig, Leipzig, Germany
8. Department of Cardiac and Vascular Surgery, University of Hamburg, Hamburg, Germany
9. Department of Cardiac, Thoracic and Vascular Surgery, St. Johannes Hospital, Dortmund, Germany
10. Department of Cardiac Surgery, University of Bonn, Bonn, Germany