1. Department of Cardiothoracic Surgery & Cardiology, St. George's Hospital, St. George's University of London, Blackshaw Road, London, SW17 0QT, United Kingdom
2. Department of Biomedical Engineering, Rayne Institute, St. Thomas’ Hospital, King's College London, London SE1 7EH
, United Kingdom
3. Departments of Surgery and Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109
USA