Jeca Pereira has done something in the streets of Timor-Leste's capital Dili that would have been nearly impossible for him just 15 months ago — he walked.

Before receiving medical treatment, the 12-year-old's heart was dangerously overworked.

Even slight exertion forced it to pump far beyond safe limits and doctors told his family his weak heart would eventually prove fatal.

Jeca was brought to Australia for a life-saving operation in 2014.

Now he has come to the busy Bairo Pite Clinic in Dili for a check-up.

"He's doing great. It was even better than we thought," says Dr Dan Murphy, known to most in the Timorese capital simply as "Dr Dan".

"Before he had trouble even getting a breath. Now he's breathing normally. He can run. Never could he do that before.

"He can climb trees, he's active. He's playing, he can study. It's dramatically different. He's back to a normal kid."

Jeca gives Dr Dan the answers you would expect of a 12-year-old boy.

"Are you eating OK?" Dr Dan asks.

"Yes," Jeca responds.

"Are you coughing?" Dr Dan asks.

"No," Jeca says.

Asked to sum up his condition, he has three words: "I am OK."

'Patients die' waiting for Australian treatment

Jeca Pereira with 'Dr Dan' Murphy at a medical check-up more than a year after a life-saving operation. ( ABC News )

Jeca is one more success for East Timor Hearts Fund, a charity that brings heart patients from Timor-Leste to Australia for treatment — but there are many others like him who need help.

"There's no cardiac care available, especially not for poor villages," East Timor Hearts Fund chair Ingrid Svendsen says.

"So when they come to Australia, by the time we get to see them and our medical team identifies them for treatment, they're incredibly ill."

Loading...

Sometimes the logistical and financial constraints cannot be overcome.

"It's like a Swiss watch without the precision getting patients to Australia. We need to organise passports and visas," Ms Svendsen says.

"Tragically, we have had patients die while we've been attempting to get them to Australia."

Those frustrations only seem to make the charity work harder.

Before the holidays, more patients arrived in Melbourne. One was 21-year-old Ana Pereira.

Like many children in Timor-Leste, Ms Pereira suffered rheumatic fever as a child. It left a vital heart valve badly damaged.

Her condition did not surprise Professor Richard Harper at MonashHeart hospital.

Working with the charity, he has operated on many Timorese patients.

An examination revealed Ms Pereira's mitral valve was far too small. It meant her heart had to pump dangerously hard.

Doctors insert a balloon into Ana Pereira's leg through to her heart. ( ABC News )

"It should open very widely, about three times that amount," he says, pointing to an image of the valve on a screen.

"And that's putting a strain on the heart."

Professor Harper leads a team at MonashHeart. They are well practiced in the procedure to fix damaged heart valves.

In the operation, a small uninflated balloon in a catheter is inserted into an artery in Ms Pereira's leg.

Then with doctors in the operating theatre carefully watching screens, the balloon was guided into her heart.

"This is often the trickiest part — actually getting it across the valve," Professor Harper says, as he manoeuvres the balloon into position.

Once the balloon is across the valve, it is inflated and deflated a number of times.

The idea is to stretch the valve, so the opening is wider, that way the heart can pump blood more easily, easing a strain that often proves fatal.

This time, it is not a perfect result. But Professor Harper is satisfied.

"She'll notice quite a bit of improvement but she may need something further done in 5 or 10 years," he says.

"Her breathing will be a lot easier. She'll be able to do more."

'Now I can walk, and run. I feel really good'

Ana Pereira now has plans to go to university and live a normal life. ( ABC News )

A week later, Ms Pereira is up and about, walking with ease and cannot get the smile off her face.

"I feel much better now, not like before. Before when I walked I couldn't breathe properly. Now I can walk, and run. I feel really good," she says.

Ms Pereira returns home with plans to go to university and live a normal life.

Back in Dili, Jeca is already doing that.

His mother says that without East Timor Hearts Fund and Jeca's treatment at MonashHeart, it would have been impossible.

"I want to thank the doctors who supported us in Australia, in Melbourne," Marquita Pereira says, as she watches her son play soccer — something that would have been unthinkable not so long ago.