1. Department of Cardiothoracic Surgery, Landspitali University Hospital, Faculty of Medicine, University of Iceland, Reykjavik, Iceland;
2. Department of Cardiothoracic Surgery, Karolinska University Hospital, Stockholm, Sweden;
3. Division of Cardiac Surgery, Yale School of Medicine, New Haven, CT, USA;
4. Department of Cardiothoracic Surgery, Turku University Hospital, University of Turku, Turku, Finland;
5. Department of Cardiothoracic Surgery, Aarhus University Hospital, Aarhus, Denmark;
6. Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy, Gothenburg University, Sweden and Department of Cardiothoracic Surgery, Sahlgrenska University Hospital, Gothenburg, Sweden;
7. Tampere University Heart Hospital and Tampere University, Tampere, Finland;
8. Lund University, Skåne University Hospital, Department of Clinical Sciences, Department of Cardiothoracic Surgery, Lund, Sweden