1. Department of Cardiology, Royal Brompton and Harefield Hospitals, Guy’s and St Thomas’ NHS Foundation Trust, Harefield Hospital , Hill End Road, Harefield, Uxbridge, UB9 6JH , UK
2. Cardiovascular Sciences, National Heart and Lung Institute, Imperial College , Dovehouse Street, London SW3 6LY , UK
3. Capital Air Ambulance , Bristol, BS48 3DP , UK