Hong Kong Derby winner Luger is eligible to recommence his career next week, at least on the training track and John Size will be monitoring the gelding's heart on a daily basis in the hope of avoiding another heart irregularity.

The five-year-old has not run since he was eased out of his Champions Mile clash with Able Friend suffering his second bout of atrial fibrillation, and a third would compulsorily end his career.

He was automatically barred from racing for six months after that performance, but can return to training after four months and that period is up on September 3.

During the summer, Size has had Luger's specific problem looked over by an expert from England and the gelding will don heart monitoring equipment when he does begin again.

"We got some information, some data for this lady before she arrived and looked him over and she's given us some equipment to monitor him more closely and see if his heart is irregular in any way at trackwork," Size said.

"It's not magic, it's equipment that has been used before and records his heart beat while he's working and when he comes back and how he recuperates. And we're hoping that it will give an indication if something isn't correct."

But Size knows the problem strikes randomly and there are no guarantees of what will happen when Luger goes to the races.

"If he comes into work and does everything right - which he probably will because that's what he's done since the first day he walked into the stable - then we find out race day, but, if this equipment shows us any reason for concern, he won't go to the races," said Size, adding that he has no firm plan for resuming Luger's race career.

"He'll need a couple of months to work up and a couple of trials and then see what's available.

“I’m not thrilled about putting him in a Hong Kong Mile to find out how he is, but that might happen, or we take another month and wait for the softer option in the Stewards’ Cup in January.”

Size said that horses who suffered atrial fibrillation problems often had larger hearts than average horses.

“The bigger heart makes them good athletes, but apparently also works against them in this scenario,” he said. “I guess we’re lucky that he was able to win the Derby between the two heart irregularities but also very unlucky to have this fantastic athlete on our hands whose oversized heart gives him this issue.”