a1 Department of Cardiac Surgery, Royal Children's Hospital, Parkville, Victoria, Australia
(Accepted September 20 1998)
Correspondence:
c1 Tom R. Karl, Department of Cardiac Surgery, Royal Children's Hospital, Flemington Road, Parkville Vic 3052, Australia. Te: 61 3 9345 5200; Fax: 61 3 9345 6386