1. Department of Cardio-Thoracic Surgery, University Medical Center Groningen, 9711 RB Groningen, Netherlands
2. Department of Cardiology, University Medical Center Groningen, 9711 RB Groningen, Netherlands
3. Department of Cardiac Surgery, San Raffaele University Hospital, Milan, Italy
4. Department of Cardiology, Academic Medical Center, Amsterdam, Netherlands
5. Department of Cardio-Thoracic Surgery, Academic Medical Center, Amsterdam, Netherlands