[1] St Bartholomews Hosp, Barts Heart Ctr, Electrophysiol Dept, London EC1A 7BE, England
[2] UCL, Inst Cardiovasc Sci, London WC1E 6DD, England
[3] Royal Free Hosp, London NW3 2QG, England
[4] Athens Univ, Med Sch, Hippokrat Hosp, Cardiol Dept 1, Athens, Greece