1. Division of Surgery, Kingston Hospital NHS Foundation Trust, Kingston upon Thames KT2 7QB, UK
2. Wessex Cardiothoracic Centre, Division of Cardiac Surgery, Southampton University Hospital NHS Foundation Trust, Southampton SO16 6YD, UK
3. Cardiac Surgery Unit, Lancisi Cardiovascular Center, Ospedali Riuniti delle Marche, Polytechnic University of Marche, 60126 Ancona, Italy
4. Department of Human Development and Health, Faculty of Medicine, University of Southampton, Southampton, SO17 1BJ, UK