1. University Department of Cardiac Surgery, Leipzig Heart Center , Leipzig, Germany
2. Louis Stokes Cleveland VA Medical Center, Department of Veterans Affairs , Cleveland, OH, USA
3. Department of Cardiology, Leipzig Heart Center , Leipzig, Germany
4. Department of Cardiology, Zentralklinik , Bad Berka, Germany
5. Department of Cardiac Surgery, Helios Universitätsklinikum Wuppertal, Witten-Herdecke University , Wuppertal, Germany