1. Medical Sciences Division, University of Oxford, Oxford OX3 9DU, UK
2. Department of Cardiothoracic Surgery, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford OX3 9DU, UK
3. Department of Cardiothoracic Surgery, University Hospital of Larissa, School of Medical Sciences, 413 34 Larissa, Greece
4. Department of Cardiothoracic Surgery, Hammersmith Hospital, Imperial College Healthcare NHS Trust, London W12 0HS, UK
5. Trent Cardiac Centre, Nottingham University Hospitals, Nottingham NG5 1PB, UK
6. Department of Cardiothoracic Surgery, Royal Brompton Hospital, Guy’s and St Thomas’ NHS Foundation Trust, London SW3 6NP, UK