[1] Univ Glasgow, Paediat Soc, Glasgow, Lanark, Scotland
[2] Great Ormond St Hosp Sick Children, Dept Cardiol, Inherited Cardiovasc Dis Unit, London, England
[3] Univ Milan, Osped Luigi Sacco, Dept Paediat, I-20122 Milan, Italy
[4] Boston Childrens Hosp, Dept Cardiol, Boston, MA USA
[5] UCL, Inst Cardiovasc Sci, London WC1E 6BT, England