No Siamese twin born with a fused heart has ever survived, but surgeons said yesterday there was a good chance of the surviving twin, who is now in intensive care, making a recovery.
The "incredibly complicated" surgery took place at Great Ormond Street Hospital in central London. The twins, from Kuwait and born five weeks premature, had been joined from the breastbone to the navel and had fused hearts and livers.
The consultant paediatric surgeon Mr Edward Kiely, who led the operating team, said: "I think we're quite pleased to have one baby alive ... We knew there was always going to be the potential that the second one would die. We were quite concerned that both would die, as has happened with conjoined hearts before."
A paediatric surgery professor, Lewis Spitz, and a consultant cardiac surgeon, Marc de Leval, also took part in the 12-hour operation.
The twins had been delivered by Caesarean section at Queen Charlotte's Hospital, west London, last week before being transferred.
It was the first time the team, the most expert in the field in Europe, had attempted to separate conjoined twins with fused hearts. Before the operation the surgeons gave the parents a 10 per cent chance of one of the twins surviving.
The major problem facing them was that only one heart was functioning properly. Mr de Leval said: "We realised that the good heart was supporting the bad heart. When we disconnected the two, the bad heart could not support the circulation of the twin who died."
He said that after the surgeons thought they had separated the hearts, they realised there was a second, hidden connection between them. It took 10 minutes to find the join.
The surgeons said the next few days would be critical. But Professor Spitz said: "The child has got a normal heart, which is a big advantage. We would be very disappointed if he did not survive."Reuse content