1. Department of Cardiothoracic Surgery; University Hospital Halle; Germany
2. Department of Gynecology; St. Elisabeth and St. Barbara Hospital; Halle (Saale) Germany
3. Department of Surgery; Hospital Aarberg, Spital Netz Bern; Aarberg Switzerland
4. Department of Internal Medicine, Cardiology; University Hospital Halle; Germany
5. Institute of Medical Epidemiology, Biostatistics and Informatics; Martin-Luther-University Halle-Wittenberg; Halle (Saale) Germany