1. Department of Cardiac Surgery, Heinrich Heine University, Medical Faculty , Duesseldorf, Germany
2. punkt05 Statistics Consultants, Life Science Centre , Duesseldorf, Germany
3. Department of Experimental Psychology, Heinrich Heine University , Duesseldorf, Germany
4. Department of Cardiac and Cardiovascular Surgery, Helios Hospital Krefeld , Germany
5. Department of Cardiovascular Surgery, Klinikum Dortmund gGmbH , Dortmund, Germany
6. Witten/Herdecke University , Witten, Germany