1. Department of Thoracic and Cardiovascular Surgery, Saarland University Medical Center, 66421 Homburg/Saar, Germany
2. Department of Cardiothoracic Surgery, Jena University Hospital, Friedrich-Schiller-University Jena, 07743 Jena, Germany
3. Department of Cardiac Surgery, Rotenburg Heart and Vascular Centre, 36199 Rotenburg an der Fulda, Germany