SO exhausted she couldn't walk home from school, little Libby Tully was living with half the energy for a girl her age.

Fast forward nine months, and the four-year-old can’t keep still after having undergone vital heart surgery that’s given her a new lease of life.

Just eight weeks ago Libby had open heart surgery after being born with two holes in her heart and complex congenital heart defects.

Unable to cure her condition, medics can only monitor her progress as she grows, giving her surgery as and when she needs it.

Libby’s mum Lynsey, 34, said: “Earlier this year Libby’s oxygen levels were down as low as 55%. She became extremely breathless and I’d have to carry her home from school.

“She was very emotional from being tired all of the time and wasn’t much of an eater.

“In September she had open heart surgery, and she’s responded really well. We were home within 10 days and for the first time in her life her oxygen levels are up at 97%.”

Libby and her brother Joel, six, were among the hundreds of babies and children getting treated to some festive fun at the weekend with an annual Christmas party staged at St James’ Park.

Organised by the Children’s Heart Unit Fund (CHUF), based at the Freeman Hospital, youngsters got to play and be children with party games, dancing and a visit from Santa.

Libby’s excitement was clear for all to see as, with her face painted like a clown, she bounded around the party with her big brother.

Her dad Rob, 39, said: “Since she came home from her operation, Libby has been like a different child. It’s so great to see. She now runs home from school and is a great little eater. The change in her is just unbelievable.”

Friends Lucy Donahu, eight, from Newcastle, and Jack Whinham, six, from Wallsend, used to come to the CHUF parties as babies having both undergone heart surgery at a young age. Now the pair attend as helpers with their mums Gill and Nicola, who are the vice chairman and chairman of the CHUF fundraising committee respectively.

Committee chairman Nicola Whinam said: “Fundraising this year has been really good. The more publicity the unit gets the more people are aware of its work. We now have more than 250 children registered with the unit from around the North East and the unit is helping more babies and children than ever before.”

Also enjoying the festivities was eight-year-old Rachel Hooley, from Cramlington, who earlier this year underwent a heart transplant.

Her mum Eve, 39, said: “In January, Rachel’s condition deteriorated. She only had to wait nine days for a new heart. You just have to take what you’re told in your stride and deal with it. We had great support from CHUF.”