1. Institute for Cardiovascular Science, University College London, United Kingdom (J.B.T., P.D.L.).
2. Barts Heart Centre, St Bartholomew s Hospital, London, United Kingdom (J.B.T., A.C., P.D.L.).
3. Department of Cardiology, Hospital Universitario Ramón Y Cajal, Madrid, Spain (C.L., J.M.).