[1] Vestfold Cty Cent Hosp, Dept Paediat, NO-3116 Tonsberg, Norway
[2] Vestfold Cty Cent Hosp, Dept Internal Med, Tonsberg, Norway
[3] Natl Hosp, Rikshosp, Dept Thorac & Cardiovasc Surg, Oslo, Norway
[4] Natl Hosp, Rikshosp, Dept Paediat Cardiol, Oslo, Norway