1. Department of Vascular Surgery, Cologne University Heart Centre, Cologne, Germany
2. Department of Cardiothoracic Surgery, Cologne University Heart Centre, Cologne, Germany
3. Department of Cardiothoracic Surgery, University of Cologne, Kerpener Strasse 62, 50937 Cologne, Germany
4. Department of Cardiac Surgery, University Hospital Oldenburg, European Medical School Oldenburg-Groningen, Carl von Ossietzky University Oldenburg, Oldenburg, Germany
5. Department of Cardiothoracic Surgery, University Hospital Magdeburg, Magdeburg, Germany