1. University College London Institute for Cardiovascular Science and Barts Heart Centre, St. Bartholomew's Hospital, West Smithfield, EC1A 7BE, London, UK
2. Institute of Nuclear Medicine, University College London Hospitals, UK
3. Oxford University Hospitals, John Radcliffe Hospital, Headley Way, Headington, Oxford, OX3 9DU, UK
4. National Institute for Health Research University College London Hospitals and Barts Heart Biomedical Research Centres, UK
5. Department of Respiratory Medicine, University College London Hospitals, 5th Floor, University College Hospital, 235 Euston Road, London, NW1 2BU, UK
6. Department of Statistical Science, University College London, London, UK