1. Department of Cardiology, Royal Free Hospital, Pond Street, London NW3 2QG, UK
2. Electrophysiology Department, Barts Heart Centre, St. Bartholomew's Hospital, West Smithfield, London EC1A 7BE, UK
3. Institute of Cardiovascular Science, University College London, Huntley Street, London, WC1 E6DD, UK
4. Department of General Medicine, John Radcliffe Hospital, Headley Way, Oxford, OX3 9DU, UK
5. Department of Electrophysiology, Sint-Jan Hospital Bruges, Ruddershove, 8000 Brugge, Belgium
6. Division of Cardiology, St. Louis University, N Grand Blvd, St. Louis, MO 63103, USA
7. Department of Cardiology, Liverpool Heart and Chest Hospital, Thomas Dr, Liverpool, L14 3PE, UK