1. Department of Cardiovascular Surgery, Hospital Clínico, University of Barcelona, Barcelona, Spain
2. Department of Thoracic and Cardiovascular Surgery, West German Heart Center Essen, Essen, Germany
3. Department of Cardiac Surgery, Sant'Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy
4. Department of Cardiovascular Surgery, Hospital Hietzing, Vienna, Austria
5. Department of Cardiac Surgery, Leipzig Heart Center, Leipzig, Germany
6. Department of Cardiothoracic Surgery, University Hospital Birmingham NHS Foundation Trust, Birmingham, UK