His heart had stopped.

"Is the patient breathing?" the Triple Zero operator asked.

"I am the patient," came the calm, if not confusing, reply.

Moments earlier, as his lifeless body crumpled to the ground, some thought the seemingly fit and healthy Blake Glennie could be dead.

"The last thing I remember was I got on my haunches and then I collapsed," the Novocastrian recalls. "And then the next thing I realised I woke back up. I was on my back and had all the team running towards me.

"I had a cardiac arrest. Some people would say yes, you've died. I don't look at it as I've died as such. If I didn't have my defibrillator, that probably would have been the outcome."

Blake's defibrillator - a small device implanted in the chest to shock the heart back to a normal rhythm if needed - was installed only as a precaution a few years prior.

"I was a reasonably decent footballer when I was younger," says Blake, making the clear distinction that it was "proper football", otherwise known as soccer.

"And I'd just been feeling a little off for a while. I went to the doctor's and said I hadn't been feeling 100 percent. It wasn't anything cardiac related, but my GP was like, look, given your family history we'll do an ECG (electrocardiogram) and blood tests just to make sure you're ok."

Blake knew his family history was marred with heart problems but didn't think they affected him. He was young, athletic and about to study medical science. Still, the picture painted before him was stark. Before Blake was even born, his uncle died while out jogging with his son, a victim of Sudden Cardiac Death, an unexpected and deadly loss of heart function. Testing years later in Blake's father and cousin would reveal a condition called familial hypertrophic cardiomyopathy (HCM), which affects the heart muscle wall and can impede the flow of oxygen-rich blood from the organ.

When Blake's tests revealed the same condition, his cardiologist didn't think an internal defibrillator was needed. It was overkill. In what some might say is a surprising move for a 20-something-year-old male, Blake sought a second opinion.

"I thought the defibrillator was just a precaution. I didn't think anything would ever happen and I always convinced myself that oh yeah, you know, I've got it if I need it but I'm not going to really need it. And then I did need it."

Blake's inherited condition affects about one in 500 people worldwide.

Clinical geneticist Dr Anne Ronan from Hunter Genetics has seen dozens of families in the Hunter Region alone with the disease.

"There's an awful lot of people in Newcastle with HCM... and [having an internal defibrillator] is becoming very common," she says.

"We now know that HCM is basically due to one of the heart muscle proteins being formed incorrectly... and so we look at the gene that codes for each muscle component to see if we can find a spelling mistake somewhere in the code."

It means that genetic testing for the condition is available, but the genetic spelling mistake for each family is different and it can take years to track down the right one and find the cause of the disease. In Blake Glennie's case, they still don't have answers.

If they did, other family members, including children, who don't have symptoms could be tested easily and given appropriate treatment, which would greatly reduce the risk of Sudden Cardiac Death. For families who have already lost someone to the disease, Hunter Genetics can analyse genetic material saved from autopsies.

If a genetic cause isn't found, relatives often have to be put under surveillance, which includes regular cardiac testing. Trying to keep track of family members is a huge task, and if a genetic cause is found in a family, some members might not even know.

"That's a big part of our role," Dr Ronan says, "We're trying to coordinate all of this and make sure all family members get the same advice and follow up, and keep that advice up to date - this is a rapidly changing area of medicine.

"Blake and a handful of other people like him have been trying to set up a network for families, individuals and young people with heart conditions, to get them to come out of the woodwork and say these are the services we need, this is what we'd like to see.

"We want to support them all with a specialised cardiac genetic clinic and clinical registry that the local cardiologists can access to help manage the families.

"A registry can help show us what families have a particularly dangerous pattern, what families have a benign pattern, and that may mean the difference between somebody getting an implanted defibrillator or not."

That in itself is a personal choice. Blake's cousin with the same condition has chosen not to have an internal defibrillator. Sometimes the unexpected can happen anyway. Blake's father died suddenly from heart complications in 2014, he was just days away from having his pacemaker replaced. Blake was with him in his final moments.

Now age 33, Blake is a positive person. He has suffered great loss and nearly died himself. But he is relaxed and happy. His experiences have changed the way he approaches life and all its finer things.

"The one thing I remember sitting and thinking was, say I did die, would I have been happy with the life I had led up to at that point?" he asks.

"And the answer was no, it wasn't. And I thought I've got so much more to offer."

And if something is wrong, he says, "see your doctor, get a second opinion, you don't know what it might change."