1. Department of Cardiothoracic Surgery, Sahlgrenska University Hospital, Gothenburg, Sweden
2. Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
3. Department of Cardiothoracic Surgery, Faculty of Medicine, Landspitali University Hospital, University of Iceland, Reykjavik, Iceland
4. Section of Cardiac Surgery, Yale University School of Medicine, New Haven, CT, USA
5. Department of Cardiothoracic and Vascular Surgery, Aarhus University Hospital, Skejby, Denmark
6. Department of Cardiothoracic Surgery, Heart Center Tampere University Hospital, Tampere, Finland
7. Department of Thoracic and Cardiovascular Surgery, Karolinska University Hospital, Stockholm, Sweden
8. Department of Surgery, Heart Center, Turku University Hospital, University of Turku, Turku, Finland
9. Department of Clinical Sciences, Lund University, Skane University Hospital, Lund, Sweden
10. Department of Cardiothoracic Surgery, Lund University, Skane University Hospital, Lund, Sweden
11. Department of Heart and Vascular Theme, Karolinska University Hospital, Karolinska Institute, Stockholm, Sweden
12. Department of Cardiothoracic Surgery, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark
13. Statistiska konsultgruppen, Gothenburg, Sweden