1. Department of Cardiothoracic Surgery, Landspitali University Hospital, Faculty of Medicine, University of Iceland, Reykjavik, Iceland;
2. Department of Cardiothoracic Surgery, Sahlgrenska University Hospital, Gothenburg, Sweden;
3. Department of Cardiothoracic Surgery, Skane University Hospital, Lund, Sweden;
4. Department of Cardiothoracic Surgery, Orebro University Hospital, Orebro, Sweden;
5. Department of Cardiothoracic Surgery, James Cook University Hospital, Middlesbrough, UK