World champion New Zealand surf life saver Devon Halligan has been forced to withdraw from the Australian Ironwoman series due to a heart problem -- but she is already plotting a return.

The Sydney-born and Gold Coast-based 20-year-old was diagnosed with myocarditis - an inflammation of the heart muscle - after she struggled during the opening two rounds of her debut season.

Halligan tired noticeably during the opening leg at Perth in late December and placed last.

She fared slightly better in the second stop on tour in Newcastle last month, beating one rival home.

The daughter of former Kiwis international Daryl Halligan, Devon was a member of the New Zealand squad that won the world team title at Rescue 2012 in Adelaide in November.

Her selection in the 17-strong Ironwoman series for the first time indicated her career was further evidence of her development.Halligan missed rounds at Portsea on the Victorian coast, last Saturday's race at Surfers Paradise and officially pulled out today.

"I am devastated to be withdrawing from the series," Halligan said.

"This was my first series, so I haven't had a chance to race and compete at the best of my ability."

Halligan, who switched allegiance to New Zealand last April, qualified for the Ironwoman series through a stand-out performance at the Australian nationals last year will target the event again in a bid to make the cut for 2014.

"The doctors gave me the all clear this week to return to training, which is very exciting after having two months off and I will be able to return to racing in a month," she said.

Series director Guy Leech was disappointed Halligan had to withdraw but her health was paramount.

"Devon is a dedicated athlete with a successful future ahead of her," he said.

"The health and wellbeing of the athletes is our number one priority and we hope Devon has a speedy recovery and is back racing soon."

- © Fairfax NZ News