Some South Island cardiothoracic patients seem likely to be redirected to other hospitals to give Dunedin more patients.
Talks have been under way for months over redirecting South Canterbury cardiothoracic patients from Christchurch to Dunedin.
Because of a domino effect, all Nelson-Marlborough cardiothoracic patients would then need to go to Christchurch.
At present, some go to Wellington, and some to Christchurch.
South Island Alliance leadership team chairman Chris Fleming said South Island DHBs were working together to try to make it happen.
No final decision had been reached, and it would be made according to a consensus model.
''This issue's been around for a while. It's vital that we get it right.''
Mr Fleming, who is chief executive of Nelson Marlborough DHB, said his board was reluctant to make the change unless it achieved the desired outcome of shoring up the service in both Christchurch and Dunedin.
''We've committed to the services being in Dunedin and Christchurch and we want the clinical people ... to sit down in the room and make that physically happen.''
Asked if it was proving to be tricky politically, Mr Fleming said, ''Everything in health is political.''
