After weeks in hospital, the 34-year-old father of three learned he had a heart condition known as Long QT, which is usually only discovered during an autopsy even though about one in 2000 Australians have the syndrome.

"I was bewildered. There was no warning, no precursor and I had no idea," Mr Donaldson said. "We need a way to detect conditions before you experience what can be quite severe consequences."

Cardiac arrests account for slightly more than 10 per cent of Australian deaths. But the quest to find a way to detect heart conditions before a crisis has made a big leap forward after a five-year project by Australian scientists.

They have developed a way explore why people who have exactly the same gene flaw that causes Long QT have such different experiences of the syndrome, from never noticed to sudden death.

The findings will enable researchers to develop more accurate diagnosis and treatment plans for a syndrome more than 100,000 Australians have.

The researchers with the Victor Chang Cardiac Research Institute created software that simulates hundreds of hearts each beating to its own genetic drum.

But the heart is a complex organ of more than a billion cells. Simulating even one heartbeat requires powerful processing machinery.

To simulate hundreds of thousands of beats, the researchers used the CSIRO's supercomputer that is among the world's 10 most powerful.

Biochemist Adam Hill led the team of computer scientists and cardiac specialists to a breakthrough report on understanding heart disturbances that was published in the most recent edition of leading global science journal Nature.

"Once we were able to simulate a couple of hundreds of hearts at once, we realised how rich and untapped a lot of information we discover through ECGs [the common heart test] actually is," Dr Hill said.

Researchers were able to explore why conditions such as Long QT create a particular signature among very different ECG results, a breakthrough in understanding why people with the same condition can present differently.

As treatments range from lifestyle changes to implanted devices, this newly honed accuracy is good news for those diagnosing and battling cardiac conditions.

Molecular cardiologist Chris Semsarian from the University of Sydney's Medical School told Fairfax Media the study was an exciting development for heart science.

"The limitation of this study is that it is only a theoretical, computational model at this stage, but that is how many of our breakthroughs start," Dr Semsarian said.

"More and more researchers are using computational models around the world, but to see it applied to Long QT is fairly unique, and great groundwork for further heart condition research."

Dr Hill said computer-assisted medical research was a rapidly growing field that had come a long way since the first cell simulations decades ago.

"I went to a computational conference and it was totally alien to me. But I spotted some guys from the CSIRO, and pestered them until we started working together and it's been a very cool learning process since then."

The CSIRO's supercomputer is able to work so efficiently by using technology developed by video game technicians to cope with the load of multiple instructions at once, rather than sequential processing of classic computers.