These mates have known each other for years and every Tuesday they cycle around Narrabeen Lake in Sydney's northern beaches for a bit of exercise, while laughing at each other as they exchange a barrage of friendly jibes.

Three years ago they were cycling, and were almost back at the car park when 'Hutch' yelled out.

"He yelled out my name, I turned around and was able just to see him passed out over his handlebars and careering off into the bush," Mr MacKee said.

Hutch had suffered a sudden cardiac arrest and his life suddenly rested in the balance of those around him - his mate MacKee, two nearby walkers Carolyn and Anne, passing jogger Tim and triple-0 call taker Donna Brotherson.

To mark the third anniversary since Mr Hutchinson survived his cardiac arrest, the two best mates have met their hero triple-0 call taker.

"It was beautiful to be able to thank her because there's no way that I think I could of got through that, we were very lucky," Mr MacKee said.

"She was the one who took on a lot of responsibility in that moment and gave great confidence."

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For Mr Hutchinson, who had already met the other first responders involved on the day, it was a very emotional moment.

"Without even saying anything I knew it was her and I put my arm around her, and it was very emotional. I had a bit of a cry," he said.

When Ms Brotherson took the call on September 25, 2018, she was a relatively new triple-0 call taker and was actually being assessed by her superiors at the time.

"This was my first solo CPR call," she said. "The pressure was horrendous. Initially when you're still finding your feet it's stressful, but then all the training kicks in."

This was Ms Brotherson's first time meeting someone she'd helped to save and it's a moment she won't forget.

"Don and everyone on scene made my job so easy, they followed all my instructions. Often when we get these calls it's an incredibly heightened situation and some people just scream," she said.

Mr Hutchinson was just 55 years old when he had the cardiac arrest, and while Mr MacKee might joke that his mate owes him more than just a few car washes for being his life saver, it's clear the impact it had on their lives.

"I haven't seen many dead people, but he was everything about what you'd imagine a dead person to look like," Mr MacKee said.

Since the emergency, Hutch and MacKee founded CPR Friendly to encourage people to learn the life saving technique.

The Victor Chang Cardiac Research Institute said the two medical episodes are very different and explains them this way.

A heart attack occurs when one of the coronary arteries in the heart becomes blocked. Without adequate blood supply, the heart muscle is starved of oxygen and if left untreated it will begin to die.

A cardiac arrest is the sudden loss of heart function, breathing and consciousness. It is typically caused by an electrical disturbance in the heart which stops the heart from pumping entirely.