A new project hopes to curb the number of young people dying from sudden cardiac arrest, by collecting data about those who have and their family members.

Sarah Harrison considers herself lucky that a cardiac arrest struck while working in a bar and not at home sleeping in bed.

"Otherwise, I would be dead," she told AAP.

Ms Harrison, now 27, can't personally remember the cardiac arrest earlier this year, nor the two days before it or several days afterwards.

Her former workmates tell her she fell, hit her head on the bar and couldn't be roused.

Luckily a doctor was visiting the venue for a knock-off drink and performed CPR as an ambulance was called.

Ms Harrison woke four days later.

"It was absolutely frightening," she said.

Within a couple of weeks, doctors discovered Ms Harrison had an underlying heart condition involving a deformity of one of her heart valves.

She bought a defibrillator in case of a repeat attack.

Ms Harrison said it's only relatively recently that medical professionals learnt that her condition put her at risk of sudden cardiac arrest, meaning there's no way her parents could have screened for it as a child and known the risks she was facing.

But she hopes a new database will help doctors be more proactive understanding sudden cardiac arrests in "young people", considered those aged 50 or younger.

The new genetic database, being launched first in Victoria, will include blood samples from young people who have died from cardiac arrest.

It will also be the first such registry in the world to include samples from family members who might also be at risk.

The project is aimed at improving diagnosis of conditions that could lead to sudden cardiac arrest, to subsequently prevent deaths.

The registry is being spearheaded by cardiologists Associate Professor Andre La Gerche from the Baker Heart and Diabetes Institute and Professor Chris Semsarian from the University of Sydney, along with the RPA Hospital.

Assoc Prof La Gerche said sudden cardiac arrest frequently occur without prior symptoms or warning.

"This highlights the need to discover new mechanisms and markers for early identification of young patients at risk," he said.

Recently-opened cardiac arrest-focused clinics at Sydney's St Vincent's Hospital and Melbourne's The Alfred Hospital, along with existing clinics at the Royal Melbourne Hospital and Royal Children's Hospital, will serve as points of contact, support and evaluation for those taking part.

Cardiac arrest - in which the heart stops beating as a whole - is distinct from a heart attack, in which blood supply is blocked to part of the heart, causing its muscle to begin to die.

About 25,000 Australians die from sudden cardiac arrest each year, including many young people.

Following the Victorian launch of the database, its leaders hope to roll it out in NSW, and then nationally.