1. Faculty of Medicine, University of Iceland , Reykjavik, Iceland
2. Department of Cardiothoracic Surgery, Landspitali University Hospital , Reykjavik, Iceland
3. Department of Pulmonology, Landspitali University Hospital , Reykjavik, Iceland
4. Department of Cardiothoracic Surgery, Sahlgrenska University Hospital , Gothenburg, Sweden
5. Department of Cardiothoracic Surgery, Rigshospitalet University Hospital , Copenhagen, Denmark