Hospital officials are trying to trace about 50 New Zealanders believed to have been implanted with faulty pacemakers.
The Australian Government this week issued a "hazard alert" for people with the St Jude Medical Tempo Pacemaker after finding they could fail without warning.
The pacemaker carries a risk of earlybattery depletion and doctors have warned some people may need to have them removed.
Ministry of Health senior medical adviser Dr Stewart Jessamine said there had been no reported problems with the pacemakers in New Zealand, but doctors were erring on the side of caution and contacting all patients.
Waikato Hospital director of cardiology Dr Clyde Wade said he was extremely concerned that doctors and patients had found out about the hazard alert through the media.
His department had been inundated with phone calls.
"It's just not acceptable. There is considerable annoyance that it appeared in the press before patients had been told about it.
"We supervise the care of hundreds of people with pacemakers but this concern affects fewer than 10 in the mid-North Island."
Those patients were expected to be contacted within 24 hours and would be judged on a case-by-case basis. Some would have their pacemakers replaced at the manufacturer's expense.
Green Lane Hospital, Auckland, said it had identified 30 patients with the pacemaker.
Warren Smith, head of cardiology, said only one or two were at risk and they would probably have their pacemakers removed and replaced.
Concerns about pacemakers are not uncommon, he said. Just two weeks ago doctors were alerted to component failure in another brand.
