A Goulburn woman will be walking 146 kilometres this month to raise money for the Heart Foundation in honour of her son who has complex congenital heart defects.

Louise Castro, 54, plans to walk six kilometres per day on her rural property as part of the foundation’s MyMarathon walk.

When Ms Castro’s son Brennan was born, he had a one per cent chance of survival. But, at 27, he is the world’s oldest surviving person with his condition.

Ms Castro said to keep herself motivated she will be reflecting on the battles her son Brennan has faced throughout his life.

“I am doing this to honour Brennan and acknowledge his strength and determination,” Ms Castro said.

“If it wasn’t for the Heart Foundation Brennan might not be with us today.

“He’s been through so much and if I can help one child with the money I raise, it’s been worthwhile.”

Ms Castro walked 140km last year, and through the support of friends and family, raised $1,370 for the cause. This year, her colleagues are also getting involved.

Ms Castro’s boss, Amy Hewson, is holding a ‘guess how many lollies’ competition to sponsor her walk.

“I have seen a few of our staff members with tears rolling down their faces when they ask Louise about Brennan,” Ms Hewson said.

“It’s all about raising awareness and Louise is an amazing advocate for Brennan.”

Ms Castro said the walk is a way for her to think about the adversities her son Brennan has encountered. She said if Brennan can do it, she can do it too.