1. Department of Cardiology and Vascular Medicine, West German Heart‐ and Vascular Center University Hospital Essen, University Duisburg‐Essen Essen Germany
2. Clinic of Thoracic and Cardiovascular Surgery, West German Heart‐ and Vascular Center University Hospital Essen, University Duisburg‐Essen Essen Germany
3. Medistat‐ Biomedical Statistics Medistat GmbH Kronshagen Germany