1. West-German Heart and Vascular Center Essen, Department of Cardiology and Vascular Medicine, University of Duisburg-Essen, Essen, Germany
2. Institute of Medical Informatics, Biometry and Epidemiology, University of Duisburg-Essen, Essen, Germany
3. Department of Cardiology, Alfried Krupp Krankenhaus, Essen, Germany
4. Witten/Herdecke University, Witten, Germany