1. Department of Cardiovascular Surgery, Inselspital, Berne University Hospital and University of Berne, Berne - Switzerland
2. University of Auvergne, IUT, Clermont-Ferrand - France
3. Department of Internal Medicine, Cantonal Hospital, Fribourg - Switzerland
4. Institute for Surgical Technology and Biomechanics, University of Berne, Berne - Switzerland