The woman who was given a mismatched heart in a transplant operation at Queen Mary Hospital is now conscious and in a stable condition.
There are no signs yet that her body is rejecting the new organ, which is of a different blood type to her own. It is not known if she has been told about the blunder.
The surgical team at the Pok Fu Lam public hospital failed to realise they were implanting a heart from a donor with rare type AB blood into a patient with type A blood until the surgeon had removed her heart and was attaching the new organ.
The 58-year-old patient, who had the transplant on Tuesday, is now undergoing plasma exchange therapy and receiving immunosuppressant drugs.
The chief executive for hospitals in west Hong Kong, Dr Luk Che-chung visited the patient in the intensive care unit yesterday morning and said she was able to nod to him.
Rejection can occur in any transplant surgery as the body treats the new organ as a foreign object, but the chances of rejection are much higher with an organ of incompatible blood type.
Cardiologist Dr Duncan Ho Hung-kwong said because the case was so unusual, there was little knowledge of the patient's chances of survival. In normal circumstances, he added, "if there is no rejection in the first week, the chances of rejection would be lower after that and the survival chance will be higher".
The blood plasma exchange, or plasmapheresis, is to wash away any antibodies produced by the body fighting the new heart. The drugs suppress white blood cells that also react against the new heart, he explained.
Whether the patient undergoes a new transplant would depend on how well the new heart is accepted and the availability of another donor heart, he said.
Last year, 17 hearts were donated and transplanted in Hong Kong, the highest number since the surgery was made available in the city about 20 years ago, said Luk. Seventeen patients were waiting for a heart transplant as of the end of last year.
Both the donor and recipient's blood type records were accurate and an investigation has been launched into how the mismatch occurred.
"Checking the blood type information is basic; it's like asking for the patient's name to make sure it's the right patient before consultation or surgery," Luk said yesterday.
He said using a computerised system would improve accuracy. The Hospital Authority's central committee on transplant services said it would continue to study ways to improve its data-matching system.
Two AB blood type patients were first identified as potential recipients for the heart, but they were in good condition at home after having artificial hearts implanted.
The donor had high blood pressure and a relatively enlarged heart - factors that brought the 58-year-old woman into focus as she might not have lived more than a week without a transplant.
The patient's family had not sought compensation so far, Luk said, but if they did, an insurance firm would handle the matter.
In a press conference on Wednesday, he apologised to the patient and the families involved and admitted that the incident was a result of human error.
Doctors involved in the surgery said they could not explain why they did not realise the mistake at the time.