They have become fierce advocates for the work of the Heart Foundation and know the importance of keeping active, doing regular exercise and living a healthier lifestyle.
Mrs Flett said there was no history of heart disease in her family and she had always considered herself a "very healthy" person until she was admitted to hospital in 2014.
It came as a "huge shock" to her when a Tauranga Hospital cardiologist told her she urgently needed open heart surgery to repair three major blockages.
"When the cardiologist told me I had heart disease I argued with him that I couldn't have heart disease as I didn't have any of the usual chest or arm pains," she said.
Mrs Flett, now aged 81, said apart from feeling tired and a pain in her stomach she had no idea she was gravely ill until she was rushed to Tauranga Hospital in February 2014.
"I had a triple bypass in Waikato Hospital on Queen's Birthday weekend that year and was so relieved to come through the surgery as well as I did and out the other side.
"It's thanks to the fantastic care I was given and the exercise regime I was introduced to and continue to follow today that I'm doing well and I'm thriving," she said.
"Heart disease has been described as a silent killer and after what I have been through I would totally agree with that," Mrs Flett said.
For the last three years, the 81-year-old has led a weekly "Keep on Your Feet" strength and balance exercise class at Kempton Park pavilion facilitated by Sports Bay of Plenty.
The exercise regime, which helps to keep people moving and invigorated, has gained a keen following with not just village residents but members of the local community.
When you retire you can become isolated and these exercise classes are not just a fun way to keep your mind and body active but also stay connected with other people, she said.
On February 20, Mrs Flett will be speaking at a "Living with heart disease" meeting at Tauranga Citizens' Club organised by the Heart Foundation.
Heart Foundation's Heart Health advocate Francesca Rae said: "Yvonne is part of our survivors' journey programme. Sharing her story help brings home to others they're not alone and there are ways to help reduce the risks of heart disease," she said.
Data from the latest New Zealand Health Survey had shown the rates of diagnosed ischaemic heart disease had increased significantly, Rae said.
To help collect during the "Big Heart" street appeal email events@heartfoundation.org.nz
Some key facts about heart disease rates in NZ:
The number of Kiwis living with diagnosed heart disease increased from 172,000 in 2015/16 to 189,000 in 2016/17. Rates increased in almost all ages.
Māori are 1.4 times more likely than non-Maori to be living with the disease.
Pacific people are 1.3 times more likely and the most deprived 1.25 times more likely than the least deprived to be diagnosed with heart disease.
Source: Heart Foundation
