1. Department of Cardiac Surgery, Mid-German Heart Center, University Hospital Halle (Saale), 06120 Halle (Saale), Germany
2. Department of Cardiac and Vascular Surgery, 35392 Gießen, Germany
3. Department of Cardiac Surgery, 54292 Trier, Germany
4. Department of Cardiac and Thoracic Surgery, 23538 Lübeck, Germany
5. Department of Cardiac Surgery, 91054 Erlangen, Germany
6. Department of Cardiac Surgery, 01307 Dresden, Germany
7. Department of Cardiovascular Surgery, Heart Center Brandenburg, University Hospital Brandenburg Medical School, Faculty of Health Sciences Brandenburg, 16321 Bernau, Germany
8. Institute of Medical Epidemiology, Biostatistics, and Informatics, Medical Faculty, Martin-Luther-University Halle-Wittenberg, 06112 Halle (Saale), Germany