1. Department of Cardiothoracic Surgery, Harefield Hospital, London, UK
2. Department of General Surgery, Whipps Cross University Hospital, London, UK
3. Department of Cardiothoracic Surgery, University Hospital Coventry, Coventry, UK
4. Department of Cardiothoracic Surgery, Southampton University Hospital, Southampton, UK
5. Department of Cardiothoracic, Kings College Hospital, London, UK
6. Department of Cardiothoracic Surgery, Hammersmith Hospital, London, UK