The honour was announced during the North Otago branch of the Heart Foundation's 30th anniversary dinner, much to Mrs Isbister's surprise.
"I feel very humbled," she said.
Mrs Isbister, who is in her 80s, has been involved with the branch since its inception.
The last life-membership was given out in 2005. Few had been awarded and it was rare for one to be given to a volunteer.
"For a branch to have a life member in its midst is something we are very proud of," branch chairman Brian Papps said.
The award to Mrs Isbister was "so well deserved".
She was still a very active member and a "mine of information", he said.
Five years ago, she was made branch patron. North Otago was the only branch in New Zealand that had been allowed a patron.
The branch raises funds, primarily to go towards research and heart-health initiatives. Education was an important priority and involved making the public aware of things they could do to improve their lifestyle and health.
In association with Healthy Active Living Oamaru, the branch helped organise cycling, running and walking activity days.
"For a small town and a relatively small group of people, we do keep ourselves busy," Mr Papps said.
The branch has an office in Ribble St.
