1. University of Cambridge,Department of Public Health and Primary Care,Cambridge,UK,CB1 8RN
2. Royal Brompton Hospital (Guy's and St Thomas' NHS Foundation Trust),London,UK,SW3 6NP
3. Zenicor Medical Systems AB,Stockholm,Sweden,11359
4. Liverpool Centre for Cardiovascular Science, University of Liverpool and Liverpool Heart and Chest Hospital,Liverpool,UK,L69 7TX