1. Department of Cardiothoracic and Vascular Surgery, University Hospital Tübingen, Tübingen, Germany
2. Department of Cardiothoracic and Vascular Surgery, Medical Centre of Johannes Gutenberg University Mainz, Mainz, Germany
3. Department of Cardiac Surgery, Queen Elizabeth Hospital, University Hospital Birmingham NHS Trust and University of Birmingham, Birmingham, UK
4. Department of Cardiac Surgery, Leipzig Heart Centre, University of Leipzig, Leipzig, Germany
5. Department of Cardiovascular Surgery, University Hospital Berne, Berne, Switzerland