1. Department of Cardiovascular Surgery, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg , Freiburg, Germany
2. Department of Cardio-thoracic Surgery, West German Heart and Vascular Center Essen , Essen, Germany
3. Department of Cardiac Surgery, University Hospital Tampere , Tampere, Finland
4. Department of Diagnostic and Interventional Radiology, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg , Freiburg, Germany
5. Department of Cardiac Surgery, Inselspital, Bern University Hospital, University of Bern , Bern, Switzerland