[1] Mayo Clin, Coll Med, Div Pediat Cardiol, Rochester, MN 55905 USA
[2] Mayo Clin, Coll Med, Div Cardiovasc Dis, Rochester, MN 55905 USA
[3] Loyola Univ, Med Ctr, Maywood, IL 60153 USA
[4] Univ Parma, Dept Pediat, Cardiol Sect, I-43100 Parma, Italy
[5] Parma Hosp, Dept Cardiac, Parma, Italy