1. Department of Cardiovascular Surgery, University Heart Centre Freiburg, University Freiburg, Freiburg, Germany
2. Medical Faculty, Albert Ludwigs-University Freiburg, Freiburg, Germany
3. Department of Cardiovascular Surgery, Hospital Hietzing, Vienna, Austria
4. Department of Cardiovascular Surgery, Landeskrankenhaus Salzburg, Paracelsus Medical University, Salzburg, Austria