The family and friends of a DJ who died suddenly while performing at a Sydney club said he appeared in perfect health before falling victim to Australia’s “silent killer”.

Alf Nguyen, 42, suffered a cardiac arrest in the middle of his set at the Tokyo Sing Song club in Newtown’s Marlborough Hotel on July 13.

Nguyen, who left behind his wife Rita McCulloch and his five-year-old son, Chauncey, appeared to be fit and healthy before his sudden death, his close friend Luke Smith told nine.com.au.

But an autopsy revealed he was in the advanced stages of ischemic heart disease and had likely lived with the condition for several years.

Nguyen was a loving father and a "music legend" who had played at all of Sydney's top nightclubs for decades. (Supplied)

His death has prompted appeals for greater awareness of heart health and awareness of the warning signs for heart disease, especially among men aged 45 and older.

Ischemic heart disease, also known as coronary heart disease, is the most common cause of death in Australia and kills about 160,000 people per year.

It’s known as a “silent killer” because of its lack of symptoms. Often the first sign of the disease is chest pain or a heart attack.

Smith, who is also a DJ, was performing alongside his friend when he collapsed without warning.

“He was playing at the time right in front of me and he grabbed his right shoulder and just fell down,” Smith said.

Nguyen was unable to be revived by paramedics and never regained consciousness, he said.

“It was pretty immediate and sudden. Alf had no idea that he had this heart condition, there were no symptoms. He didn’t pick up on it and neither did his wife,” he said.

Alf Nguyen, pictured with his five-year-old son Chauncey. (Supplied)

Nguyen had played at Sydney’s top nightclubs for decades and was known by his DJ name A.L.F or First Grandson.

Smith said he had known Nguyen since primary school when they both attended the Our Lady Star of the Sea Catholic Primary School in the Sutherland Shire.

Nguyen and his family were Vietnamese refugees and he arrived in Australia when he was 10 years old, Smith said.

“His aunt was one the first Vietnamese boat people and then applied for the family to come across through the Australian government.”

Although he was unable to speak English at first, Nguyen embrace his new life in Australia with characteristic gusto, Smith said.

“The one thing about Alf is he just lived for life,” he said.

“He played cricket, rugby and basketball. He loved basketball. He grabbed the opportunities of coming to this country with both hands and he gave everything a go.

“At the end of the day he actually sounded more ‘ocker’ than the rest of us.”

Out of high school, Nguyen pursued his love of electronic music, performing at under 18’s gigs before moving on to play at most of Sydney major nightclubs over the years.

He was also a radio host on 2SER and recorded his own music with the label Elefant Traks.

“Everyone loved him, he was just very genuine” Smith said, adding that his friend often mentored younger musicians.

“He checked his ego at the door. He was always happy to help people grow. If you sent him music he would listen and give you feedback. He was very inclusive and trying to create a community rather than being above that.”

Above all else, Nguyen was a devoted dad and family man, Smith said.

“Even before he had his son Chauncey, among our mates that had kids he was always the clucky one. He was always playing with the kids,” he said.

Nguyen and his wife had recently received challenging news, with Chauncey being diagnosed with autism, Smith said.

“He was a loving father and he was ready to step up even further with the diagnosis of autism of his son. He was actually ready to quit work even to focus on that,” Smith said.

Alf Nguyen with his wife Rita McCulloch and son Chauncey, who was recently diagnosed with autism. (Supplied)

Friends have set up an online fundraiser to help relieve the financial burden for Nguyen’s wife and son.

But Smith said the most important message Nguyen’s family and friends wanted to share was about the risks of heart disease.

“This is the number one killer in Australia and I didn’t even know. So the point is that it’s really prevalent in society, and people need to make sure they are aware of the risks and go and see a doctor about it,” he said.

What is ischemic heart disease?

Cia Connell is the Heart Foundation’s clinical manager.

For people with ischemic heart disease, a build-up of fat deposits led to a narrowing of the arteries in the heart, Ms Connell said.

“Ischemic heart disease is a condition where there are fatty deposits lining the arteries of the heart. And this can cause things like hearts attacks, because the heart is not getting enough blood supply,” Ms Connell said.

The disease can lead to a heart attack, and sometimes a cardiac arrest, where the heart stops beating and a person suddenly stops breathing.

Although ischemic heart disease usually had no symptoms, there were often warning signs in the lead-up to a heart attack, she said.

“People can have no symptoms at all. But they can sometimes have a hint something is wrong. The classic one is chest pain but others can be pain, pressure or heaviness in the chest, neck, jaw or back.”

“You can also be feeling generally unwell or fatigued. They can be kind of vague symptoms. Some people might have had those symptoms but not said anything because they thought it was something else.

“We encourage people to be aware of these warning signs and to call triple zero if they’ve had them for 10 minutes or more.”

In order to prevent heart disease, it was important that people looked after themselves by keeping on top of the common risk factors, like high blood pressure and high cholesterol, Ms Connell said.

“If someone is aged 45 or more, 35 for Indigenous Australians, we recommend they see their doctor for a heart health check, where they check up on all these risk factors,” she said.