1. Medical Sciences Division, University of Oxford, Oxford OX3 9DU, UK
2. Department of Surgery and Cancer, Imperial College London, London SW7 5NH, UK
3. Department of Cardiothoracic Surgery, Maastricht University Medical Centre, 6229 HX Maastricht, The Netherlands
4. Department of Cardiothoracic, Transplant and Vascular Surgery, Hannover Medical School, 30625 Hannover, Germany
5. Department of Cardiothoracic Surgery, University of Thessaly, 38221 Larissa, Greece
6. Department of Cardiothoracic Surgery, John Radcliffe Hospital, Oxford OX3 9DU, UK
7. Department of Cardiothoracic Surgery, UPMC Heart and Vascular Institute, University of Pittsburgh, Pittsburgh, PA 15224, USA
8. Department of Cardiology, West German Heart and Vascular Center Essen, University Hospital of Essen, University Duisburg-Essen, 45138 Essen, Germany