Laura Aisbett will never forget the moment she discovered her husband's body.
Stuart was lifeless, face down on the floor, draped in the insulation mats he'd been installing in the ceiling of their shed, just metres from their newly-completed home.
"I just remember as soon as I saw him, I just started screaming," she said.
"The screams woke me up, kept me awake for weeks, for months, afterwards. Even now, if I'm having a night terror, I'll wake up screaming with visions of Stuart lying there."
Stuart had suffered a sudden cardiac arrest and couldn't be revived.
He was 34. He didn't smoke, rarely drank, and was fit and healthy. He didn't have any underlying medical conditions and there were no warnings of what was to come.
His heart simply stopped beating.
Four days after Stuart's death, Laura discovered she was pregnant with their child, a baby they'd been trying for after a miscarriage.
"It was the most stressful nine months of my life. It really was quite difficult without Stuart here, he didn't know he was going to be a dad," she said.
"I think that he would have been a really good dad."
That was in 2020. Their daughter, Dulcie, is now 18 months of age.
She's healthy and cheeky and, according to Laura, has all the mannerisms of the father she'll never meet.
Stuart's death was ruled an unexplained cardiac death. The most likely culprit was a genetic mutation.
That has Laura concerned for her daughter's health.
"We don't know whether Dulcie is going to die the same way and that does play on my mind every day. It's likely there's a possibility that it is genetic," she said.
'Frightening' figures
Laura's search for answers led her to the Baker Heart and Diabetes Institute in Melbourne.
It recently published the results of a study looking into the causes, circumstances and potential prevention of cardiac arrest in younger people.
The researchers examined hospital, ambulance and forensic data for people aged 50 years and under who had a cardiac arrest in Victoria between mid-2019 and mid-2021.
Their findings have been published in the peer-reviewed journal Europace and involved a review of 1,319 cases.
One of the most startling discoveries was that about a quarter of all people aged under 50 who died during that time period, died as a result of sudden, out-of-hospital cardiac arrest, something pointed out by Baker Institute cardiologist and report co-author Elizabeth Paratz.
"We were very surprised by that figure," Dr Paratz said. "Cardiac arrest is a leading cause of death among young people. To put that in perspective, it's more than five times the road toll in that same age group."
Researchers found that, in younger people, cardiac arrest was more likely to be the result of a genetic mutation and many didn't have any symptoms.
For older people, cardiac arrest is more likely to be caused by a blockage of the coronary arteries or a weakness in the heart muscle.
While around half of the cases reviewed were later found to have an underlying cardiac cause, many didn't have any symptoms or obvious cause.
"The traditional figure had been that, maybe, up to a third of people who have a cardiac arrest, the cardiac arrest is the first sign of trouble — but that was for all ages," Professor Paratz said.
"In young people who appear outwardly healthy, that figure was even more frightening — it was 77 per cent."
The study also found younger people who experienced an unexpected cardiac arrest disproportionately did so while exercising.
However, Professor Paratz said, that didn't mean people should avoid exercise because physical activity is also good for heart health.
Instead, she said, people had a greater chance of survival if more people were trained in first aid.
"That reaffirms the importance of having defibrillator availability and people trained in CPR across Australia, but particularly in areas of increased risk, such as sporting clubs," Professor Paratz said.
'We don't know what's causing these deaths'
Rajesh Puranik — a cardiologist with the Royal Prince Alfred Hospital in Sydney — has reviewed the study's findings.
He said the rate of unexpected cardiac arrest death had significantly increased in the past three decades and doctors now needed to figure out why.
"In this cohort, it's a premature onset of cardiac disease, which means that these people were born with a genetic predisposition," Professor Puranik said.
"Therein lies the avenue for where we could make an impact: We could understand the cause by running genetic tests on these patients."
That's where the Baker Institute steps in.
It's helping to develop what's known as the UCD Registry, which collates things such as blood and DNA samples from younger people who've had an unexplained cardiac arrest.
Researchers hope the registry will help them identify other genetic conditions or mutations that could put someone at an increased risk of premature cardiac arrest.
The details of Laura Aisbett's husband, Stuart, have been included in the registry.
Researchers haven't found a mutation to explain his death yet. However, as the registry grows, that may change.
If it does, Laura may finally get some answers. That could be life-changing if Dulcie shares the same mutation.
"If it comes out that Dulcie has the same gene, then we're able to do something about it, something as simple as taking a tablet," Laura said.
"We don't know what is causing these deaths. I think that's why the research is so important."
