Questions are being asked about whether there is any link between Covid-19 and Shane Warne's heart troubles that led to his tragic death at just 52.

The cricket legend — who contracted Covid twice — died last week in Thailand, after unsuccessful efforts to revive him when he was found unresponsive in his room by friends.

An autopsy declared Warne died of natural causes and his body was flown home to Melbourne via private jet on Thursday night.

Warne was infected with coronavirus in England last August and in the weeks before his death, revealed to the Herald Sun he had actually contracted the virus a second time months after his original diagnosis.

"It was only like a little flu the second time," Warne told the Herald Sun. "The second time was just a bit of a sniffle and the first time I was quite bad."

A study conducted by Washington University, reported in Nature Medicine, found after one year of contracting Covid, those who had tested positive had a 72 per cent increased rate of heart failure and their risk of heart attack increased by 63 per cent.

But there is still uncertainty over the link between Covid and heart issues.

"The way Covid-19 infection might cause cardiovascular problems remains unclear," the authors of the Washington University study said.

Murdoch University Pro-Vice Chancellor for Health Sciences, Professor Jeremy Nicholson, has investigated biochemical abnormalities in the blood of Covid patients and how they are related to risk markers for heart disease.

"We published a paper a week ago showing that Covid-19 causes a major shift in cardiovascular risk markers," he told news.com.au.

Nicholson said there was a "significant possibility" an underlying heart condition would be accelerated by Covid.

In the case of Warne, he said this was particularly true as he reportedly used a ventilator to speed up his recovery.

"SARS CoV-2 infection causes inflammation that can lead to atherosclerosis," he said.

Nicholson said the separate paper in Nature Medicine showed the rate of multiple cardiovascular events and problems were greatly increased for up to a year in someone who had been infected with Covid.

Shane Warne's son Jackson (left) is grieving the loss of his best mate. Photo / Getty Images

However, Nicholson said it would be very difficult to prove that Warne had died as a direct result of Covid.

"What is strange is that it was reported that he was placed on a ventilator to minimise his chances of getting long Covid — some irony there," he said.

Although this has not been proven, Nicholson said using a ventilator could increase the risks of cardiovascular disease following Covid infections.

"We do know that SARS CoV-2 infections are highly atherogenic in the acute phase [cause hardening of the arteries] and that impacts on heart attack risks and strokes."

He said many people already understood pre-existing conditions such as diabetes could be linked with an increased risk of severity of Covid, but conversely Covid could also increase the severity of these pre-existing conditions.

"Shane may well have had some sub-clinical level pre-existing atherosclerosis [this is very common in men over 40] that was then accelerated by Covid-19. This is just speculation but it does highlight the increased risk at the population level for people who have had Covid-19, especially in its more severe forms," he said.

"I am afraid that we are likely to see more of these hidden aspects of long Covid as time goes on."

Former doctor for the Australian men's cricket team, Dr Peter Brukner, suggested this week Warne's heart problems were a long time coming.

"Warnie, if he had heart disease, which sounds like he did, you know, that didn't happen overnight in Thailand," Brukner said in an interview with Triple M Perth.

"It's been happening for 20, 30 years from smoking, poor diet, etc, etc."

After speaking with Warne's family, police revealed the cricket great had been suffering chest pains before he flew from Australia to Koh Samui.

There has been speculation as to whether Warne's recent diet played any part in his shock death, that has sparked an outpouring of emotional tributes from around the world.

Dr Peter Brukner suggested that Warne's heart problems were a long time coming. Photo / Getty Images

Warne's manager James Erksine said on the weekend the leg-spinning legend was essentially consuming only fluids for 14 days shortly before he passed.

"I didn't know about that [Warne's heart issue]. I did know from Helen, his secretary, that he'd had a bit of a chest pain and also was sweating last week but I only found that later on after he'd died. I didn't know that at the time," Erskine said on Weekend Today.

"He did go on these ridiculous sorts of diets and he just finished one, where he basically only ate fluids for 14 days and he'd done this three or four times.

"It was a bit … all or nothing. It was either white buns with butter and lasagne stuffed in the middle or he would be having black and green juices.

"I don't know, he obviously smoked most of his life. I don't know, I think it was just a massive heart attack. That's what I think's happened."

- by Caris Chang and James Matthey, news.com.au