12 在下列何種情況下，作異位心臟移植（heterotopic transplantation）比正位心臟移植（orthotopic transplantation）來得比較適當？

捐贈者有嚴重的肺動脈高血壓捐贈者的心臟遠小於受贈者所需

受贈者有急性病毒性肝炎時受贈者與捐贈者血型不符合

捐贈者的心臟遠小於受贈者所需

Heterotopic procedure

In the heterotopic procedure, the patient's own heart is not removed before implanting the donor heart. The new heart is positioned so that the chambers and blood vessels of both hearts can be connected to form what is effectively a 'double heart'. The procedure can give the patients original heart a chance to recover, and if the donor's heart happens to fail (e.g. through rejection), it may be removed, allowing the patient's original heart to start working again. Heterotopic procedures are only used in cases where the donor heart is not strong enough to function by itself (due to either the patient's body being considerably larger than the donor's, the donor having a weak heart, or the patient suffering from pulmonary hypertension).