1. Department of Cardiothoracic Surgery Heart Center of the University Hospital of Cologne Germany
2. Department of Thoracic and Cardiovascular Surgery West German Heart Center University of Duisburg‐Essen Essen Germany
3. Department of Cardiac Surgery University Hospital Münster Münster Germany
4. Department of Cardiac Surgery University of Bonn Germany
5. Institute of Medical Computer Science, Biometry and Epidemiology University of Duisburg‐Essen Essen Germany
6. Department of Mathematics and Technique Koblenz University of Applied Science Remagen Germany