Cardiac surgery delays are causing backlogs across Waikato Hospital, with wait times ballooning by up to eight weeks, doctors say.
It means patients are taking up vital bed space in other specialities while they queue for their operation.
Cardiac Society of New Zealand chairperson Dr Martin Stiles said the cardiology department at Waikato Hospital was resourced for 54 beds, but last week had 109 patients.
Stiles - who was a cardiologist at Waikato Hospital but spoke in his role as chairperson - said the overflow was spread across other departments and was known as bed-blocking.
It contributed to delays in the Emergency Department, where cardiac and other patients were forced to wait for a ward bed, leaving sick people stranded in the waiting room and in ambulances outside.
The cardiology department performed eight surgeries per week; Four for inpatients who had already suffered a heart attack, and four for those waiting at home for elective surgery.
"At the moment we have 20 inpatients waiting for cardiac surgery, so it's not difficult maths to say that if you come in today with a heart attack and need cardiac surgery you will wait four or five weeks."
Health New Zealand said the average wait time at Waikato Hospital was 29 days, but Stiles said this was skewed by patients with urgent need who got their surgery much quicker based on clinical priority.
"Those patients who are not having so many symptoms are waiting on the ward a long time. One of the patients recently gone (for surgery) this week waited 54 days."
Waikato previously sent some patients home to wait, but Stiles said that was stopped because several needed to be readmitted and two had adverse outcomes.
Stiles said resource was the biggest cause of delays including equipment failure, exhausted surgeons, and hospital workload.
Bed block in intensive care, where cardiac patients needed post surgery care, was also a contributor.
"In Auckland there's a cardiovascular intensive care unit so there is some ring-fenced beds dedicated to cardiovascular patients who are coming from surgery.
"In Waikato if there's a multi-vehicle smash, or an outbreak of meningitis or something that would take up beds in intensive care then the cardiosurgical waitlist that gets cancelled."
At one stage Waikato - which takes patients from Taranaki, Gisborne, Rotorua, Taupō, and up to Pookeno - was sending cardiac surgery patients to Auckland and Wellington, but that had stopped.
The public hospital had also used neighbouring private hospital Braemar to perform some surgeries.
There are five cardiac surgery units in New Zealand including Auckland, Hamilton, Wellington, Christchurch and Dunedin.
The shortest wait for surgery was in Wellington at two to three weeks where 11 patients were waiting, according to interventional cardiologist Dr Sarah Fairley.
Speaking in her role as chairperson of the New Zealand Cardiac Intervention Group, Fairley said even this was beyond what clinicians felt was acceptable and international guidelines.
She said underfunding and resourcing contributed to the problem.
"But yet we are being told there's no extra funding for more staff, there's no extra funding for more beds, and in some areas we're using equipment that is outdated and you could argue not fit-for-purpose but there's no extra funding for that."
Fairley said cardiology patients became more complex with long waits in hospital.
"That has a knock-on effect on the outpatient work so the outpatient waits in particular have ballooned and have gone beyond what we would think is acceptable as clinicians and that's both in cardiac surgery and cardiology."
It meant when the patient came to their elective procedure or surgery their condition had changed and they might have a more complex problem than before, she said.
Health New Zealand group operations director Michelle Sutherland said health services continued to experience significant pressures due to sustained high levels of acute demand and workforce shortages, and this was having an impact on all specialities, including cardiac services.
She said outsourcing to private facilities such as Braemar Hospital allowed Te Whatu Ora to manage service gaps, particularly with positions that were hard to recruit to, such as intensivists.
"This does not take resources away from the public health sector."
Sutherland said the number of cardiology patients at Waikato Hospital varied but there were higher volumes in the past couple of weeks, and patients referred to other public hospitals for their surgery provided positive feedback.
Asked about resourcing, she said much of the equipment at Waikato Hospital was "state-of-the-art", including advanced monitors in the theatre and intensive care, as well as cutting-edge theatre equipment, instruments, and medical implants.