[1] CHILDRENS HOSP, DIV CARDIOL, PHILADELPHIA, PA 19104 USA
[2] WASHINGTON UNIV, SCH MED, DEPT PEDIAT, ST LOUIS, MO 63130 USA
[3] ST LOUIS CHILDRENS HOSP, ST LOUIS, MO 63178 USA
[4] UNIV MINNESOTA, SCH MED, DEPT PEDIAT, MINNEAPOLIS, MN 55455 USA
[5] UNIV MINNESOTA, VARIETY CLUB CHILDRENS HOSP, MINNEAPOLIS, MN 55455 USA
[6] UNIV PENN, SCH MED, DEPT PEDIAT, PHILADELPHIA, PA 19104 USA