1. German Society for Thoracic and Cardiovascular Surgery, Langenbeck-Virchow-Haus, Berlin, Germany
2. FOM Hochschule fuer Oekonomie and Management, Essen, Germany
3. Department of Thoracic and Cardiovascular Surgery, University Kiel, Kiel, Germany
4. Department of Cardiac Surgery, University Bonn, Bonn, Germany
5. Clinic for Thoracic and Cardiovascular Surgery, Heart and Diabetes Center NRW, Bad Oeynhausen, Germany
6. Department of Cardiac Surgery, University of Leipzig, Leipzig, Germany