1. Department of Cardiology, North West Heart Centre, Manchester University Hospitals Foundation Trust, England (A.R.S., E.A., S.S., S.K., M.Z.).
2. Department of Medicine, University of Adelaide, South Australia, Australia (A.R.S.).
3. Department of Medicine, University of Manchester, England (E.A., S.S., S.K.).
4. Department of Medicine, University of Southampton, England (M.Z.).