IT is hard to imagine that this happy little girl is alive thanks to a calf’s vein used to repair her heart.

Megan Mills from Creekmoor, Poole, needed major surgery days after she was born weighing just five pounds 13 ounces.

Her tiny heart was missing an artery, leaving it unable to pump blood properly around her lungs.

But thanks to groundbreaking surgery at Southampton Hospital it was repaired using the jugular vein from a dairy calf.

Now, as she comes up to her second birthday tomorrow, Megan’s mum Joanne said her daughter has confounded doctor’s expectations.

“She’s just a superstar,” she said.

“Doctors look at her scans and tell us how poorly she is, but then they look at her and just can’t believe it.

“Nothing slows her down. She has medicine three times a day and unfortunately has a large scar. That’s a constant reminder of what she’s been through, but she’s running around doing everything normally.

“It’s hard to believe two years ago I thought I wouldn’t have her for more than a couple of days. She really has a fighting spirit.”

When Megan was diagnosed with the rare condition Truncus Arteriosus Doctors said a calf’s vein was her only option as her heart was too small for the manmade version.

Joanne, 30, added: “It was very strange to think of at the beginning – almost something alien, but then you realise that thing is keeping her alive – keeping her with us – and we’re just so grateful.”

Surgeon Marcus Haw said: “She has made a remarkable recovery and we are thrilled.”

Megan will need a number of operations as she outgrows the replacement part, and throughout her life each time it wears out.

She also has a leaking valve in her heart which will have to be operated on.

But both Joanne and her husband Paul, a chef, hope their little fighter will continue to surprise everyone.

“She has too much going on to be slowed down by anything,” added Joanne.

“Too much mischief to be getting into!”