1. Primary Care Unit, Department of Public Health and Primary Care, University of Cambridge, Cambridge, United Kingdom
2. School of Clinical Medicine, University of Cambridge, Cambridge, United Kingdom
3. Faculty of Medicine, National Heart & Lung Institute, Imperial College London, London, UK
4. Zenicor Medical Systems AB, Stockholm, Sweden
5. Liverpool Centre for Cardiovascular Science, University of Liverpool and Liverpool Heart and Chest Hospital, Liverpool, United Kingdom