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09 October 2018

Scientists know genes are responsible for roughly half your chance of having a heart attack, but they didn't know which genes were important.

Now, in a huge world-first study, Australian scientists say they have discovered the DNA patterns that can raise our risk.

People with high-risk DNA are more than four times more likely to have a heart attack than people with low-risk DNA, their study reveals.

Meanwhile, some women with the right DNA are at extremely low risk of having a heart attack even if they have high blood pressure and high cholesterol.

And healthy people with a high-risk score have the same chance of having a heart attack as people with high blood pressure and high cholesterol but a low genetic risk score.

The ''game-changing'' study, led by Australian scientists, is a major step towards creating a DNA test to predict people's risk of a heart attack.

The team behind the study used supercomputers and machine learning to study DNA from almost half a million people and generate a ''genomic risk score'': your chances of having a heart attack based solely on your DNA.

Genomics is a new way of analysing DNA. Rather than trying to find single genes that influence heart attack risk, the researchers use supercomputers to study millions of variables across people's entire DNA blueprint to look for patterns.

“It’s inevitable that genomics is going to provide us with a way of providing a risk test on top of classical risk factors in the future. This is a big step towards that,” said Professor Garry Jennings, the Heart Foundation’s chief medical adviser. The foundation was not involved in the study.

Professor Chris Semsarian, who studies the genetics of heart disease at Sydney's Royal Prince Alfred Hospital, called the study a game changer.

Scientists have known for a long time that DNA plays a huge role in our risk of having a heart attack. However, attempts to find so-called ''heart attack genes'' have failed, leaving doctors reliant on measuring clinical risk factors: smoking, cholesterol levels, blood pressure, diabetes.

But these risk factors are imprecise and miss many people who are healthy but still have a heart attack.

“If you go into our coronary care units you have patients who are thin, who are young, who don’t seem to have any risk factors, and they have a heart attack. They are left wondering, ‘Why did this happen to me?’ ” said Professor Steve Nicholls, a leading heart health researcher at the South Australian Health and Medical Research Institute.

To create a better test, researchers at the Baker Heart and Diabetes Institute and the University of Cambridge trawled through the DNA of about 480,000 people in Britain.

About 22,000 of those people went on to have heart attacks.

Using supercomputers and machine learning, the researchers compared the DNA of those who had an attack with that of those who did not, and were able to isolate the genes that put people at risk.

Using that data, they were able to generate a ''genetic risk factor'' – your chances of having a heart attack based on your DNA.

“The availability of cost-efficient genetic testing for future heart attacks is imminent and has the potential to transform primary prevention of disease as we know it,” said Baker Institute researcher Associate Professor Michael Inouye, the study’s lead author.

Sue Daperis has lost her father, grandfather and three brothers to heart attacks – and has had two of her own.

“I felt a tightening and heaviness on my chest. I also started to feel my peripheral vision was fading – I thought I was going to black out," she says.

“I’m so happy about this test. It’s so important. It’s all too late for my beautiful brothers, but if it can save lives, that’s what it’s all about.”

The research was published on Tuesday in The Journal of the American College of Cardiology.

This article first appeared in The Sydney Morning Herald, 9 October 2018.

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