1. Department of Cardiothoracic Surgery, Ruhr University Hospital Bergmannsheil, Bochum, Germany
2. Department of Internal Medicine, St. Anna Hospital, Herne, Germany
3. Department of Medical Statistics, Institute of Medical Statistics and Computational Biology (IMSB), University Hospital of Cologne, Germany
4. Department of Cardiology and Angiology, Ruhr University Hospital Bergmannsheil, Bochum, Germany