1. Department of Cardiology; Medical University of Vienna; Wahringer Gürtel 18-20, A-1090 Vienna Austria
2. Center for Medical Statistics; Informatics and Intelligent Systems, Section for Clinical Biometrics; Wahringer Gürtel 18-20, A-1090 Vienna Austria
3. Department of Cardiac Surgery; Medical University of Vienna; Wahringer Gürtel 18-20, A-1090 Vienna Austria