Former New Zealand all-rounder Chris Cairns is in an intensive care unit in a Sydney hospital after undergoing further heart surgery.

Cairns suffered a "major medical event" in Canberra late last week and initially underwent an operation in the capital city.

The 51-year-old's wife, Melanie, on Wednesday revealed he has been transferred to St Vincent's hospital in Sydney, where has had undergone another operation.

"As has now been widely reported in the media, Chris suffered a major medical event in Canberra late last week," she said in a statement.

"He initially underwent surgery in Canberra, but the seriousness of his condition is such that he has now been transferred to St Vincent's hospital in Sydney, where he has undergone further cardiovascular surgery.

"Chris' family and friends are heartened by the respectful and warm manner in which this terrible news has been reported, and received by the public, both in New Zealand and around the world, and thank everyone for their warm wishers, prayers and kind words.

"For now, no further statements will be make regarding Chris' situation, and the Cairns family asks that people continue to respect their privacy as they deal with this difficult, upsetting and concerning situation."

New Zealand Cricket CEO David White said: "We're deeply concerned to hear of Chris Cairns' medical emergency.

"Our thoughts are with his family in Australia and here in New Zealand. Chris is a much-loved husband, father, and son - and remains one of our finest all-rounders. We hope he's able to make a full recovery."

Cairns played 62 Tests, 215 ODis and two Twenty20 games for the Black Caps between 1989 and 2006.