1. Division of Cardiac Surgery, Massachusetts General Hospital, Harvard Medical School , Boston, MA, USA
2. University Clinic of Cardiac Surgery, Leipzig Heart Center, University of Leipzig , Leipzig, Germany
3. Cardiac Ultrasound Laboratory, Massachusetts General Hospital, Harvard Medical School , Boston, MA, USA
4. The Second Department of Internal Medicine, The University of Occupational and Environmental Health , Fukuoka, Japan
5. Division of Cardiac Surgery, Baylor College of Medicine , Houston, TX, USA