Crucial genetic role in sudden cardiac deaths in young revealed

One family understands the pain more than most of the role that genetics plays in sudden cardiac deaths in young, seemingly healthy individuals.

When Victoria Parkes’ 25-year-old big sister Claudia died of a sudden cardiac arrest in 2002, it was considered a tragic mystery. Like the infant version of sudden infant death, it was referred to as Sudden Adult Death Syndrome.

In the years to follow, as the human genome was mapped and genetic testing became available, Ms Parkes would find out that a genetic mutation was stalking the family on her father’s side.

Not only did her sister carry a rare gene linked to sudden cardiac arrest, she did too.

Her cousin on her father’s side also had a sudden cardiac arrest in her mid-20s. Now Ms Parkes’ son, Zac, carries the gene as well.

“We had a normal childhood by sister and I, and then one day when my sister was 25 and I was 23, she had a sudden cardiac arrest and there were not prior symptoms, nothing. She was happy, healthy and vibrant 25-year-old,” the now 44-year-old Canberra mum said.

“That was 2002. It was before our understanding of genetics. At that time, sudden cardiac

arrests weren’t publicised and we didn’t know, but it came back from the coroner no cause of death, no cause of death, undetermined.”

Victoria Parkes (right) with her sister Claudia who died in 2001 from a sudden cardiac arrest.

Claudia’s death led the family to investigate possible causes.

“There were structural problems with my heart and we wanted to know if it was a family thing, my parents, having lost a daughter didn’t want to lose me, so I was 25-ish there was a lot of concern if I went to sleep and did not wake up, so we did fit me with a defibrillator then, then my cousin on my dad’s side of the family, he had two girls and then my cousin had a sudden cardiac arrest and luckily she was able to be saved. She was mid-20s,” Ms Parkes said.

Victoria Parkes and her son Zac, 7. Both carry a gene mutation linked to cardiac arrest. Zac will need a defibrillator fitted at age 11.

Ms Parkes went on to have a cardiac arrest herself at age 35, but the defibrillator saved her life.

Her own daughter was spared to deadly gene, but her son has inherited it, despite undergoing pre-implantation genetic testing through IVF.

“We knew what the gene was and we went through IVF to do pre-implantation genetic diagnosis so we could test for the gene,” Ms Parkes said.

“It didn’t work well for us, we had three eggs, one had major abnormalities, and the other had the gene and on the third it didn’t work, we didn’t know if we could go it all again, so we used the third embryo where we didn’t know the result and my son was born and he does have the genetic heart condition.

“He is seven now, we have defibrillator at school and at home and he will get one put in at age 11.”

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The mutation on a gene known as ACTN2 causes rhythm problems and structural problems and as far as anyone know, it is so rare, it is thought to affect only one in 22 million.

Victoria Parkes (left) and her big sister Claudia as children. Both carried a genetic mutation linked to sudden death. Claudia died at age 25 in 2001.

“Once we found out what the gene was we all got tested and confirmed I had it, my cousin had it, my sister had it and both my female cousins had it. It came down from the paternal side,” she said.

TRAGADY (Trans-Tasman Response Against sudden Death in the Young) set up in 2008 aimed to identify familial genetic causes and found “an adequately detailed investigation of sudden death in children and young adults can identify inherited cardiac disease in more than 40 per cent of cases”.

Remarkably, Ms Parkes husband Steve Bridle also carries a different mutation that also leads to sudden cardiac arrest. He lost his sister Kathryn Young in 2017 to a cardiac arrest, she was only 30 years old.

Victoria Parkes' husband Steven Bridle pictured with his sister Kathryn Young who also died of a sudden cardiac arrest in 2017.

“Not sure the odds, but pretty unbelievable two people got married with different genetic cardiac mutations causing sudden death?” Ms Parkes said.

Professor Chris Semsarian from the Centenary Institute said as ‘molecular autopsy’ is now carried out on any young person who dies suddenly, adult or child.

“So DNA from the post mortem, we bring it to the lab, we study all the known genes and try and find the cause. And the reason why per cent 60 per cent of those cases have a genetic basis,” he said, adding there are treatments that can save those who carry the genes.

“I knew your I carried a gene that could lead to sudden death, there‘s plenty of things we can do to prevent that happening. The challenge is knowing who’s at risk. And that’s why investigating the family is so important.”

In babies under the age of one presumed to have died of sudden unexpected death, Prof Semsarian said around one in 20 have a genetic cause.

“We think that probably, maybe up to 5 per cent of cases are actually caused by genetic faults,” he said.

Originally published as Crucial genetic role in sudden cardiac deaths in young revealed