He was recovering from a heart transplant operation.

他正从心脏移植手术中康复。

《柯林斯英汉双解大词典》

While heart transplant surgery is no easy feat for doctor or patient, it's a surprisingly straightforward operation with high odds of survival and recovery for transplant recipients.

虽然心脏移植手术对医生和病人来说都不容易，但它目前仍然是让患者生存和恢复最好的方法。

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But as he turned 15 his condition deteriorated and a heart transplant operation was carried out last month.

BBC: Zena, Andrew and Andrew Humphrey

Sometimes the heroic medical interventions he describes are futile: A desperately sick illegal immigrant a Guatemalan woman who arrived in the U.S. with a parasitic disease affecting her heart is given a heart transplant, but after the operation she dies anyway.

WSJ: Book Review: Twelve Patients

The UK's first baby heart transplant survivor has celebrated a quarter of a century since her historic operation.

BBC: Kaylee Davidson-Olley marks 25 years with new heart