Her surgeon had tried his best to correct the problem but thought the organ was so badly damaged that there was no hope.
As a last-ditch attempt to save Kirsty's life, he decided to cut away a third of her heart, enlarged because of her condition, in case that restarted it.
And against all the odds, it once again began to beat. For Professor Stephen Westaby, that, in itself, was a miracle. But ten years on, Kirsty's heart has proved even more of a surprise.
For it has healed itself in a way experts never thought possible, and is now the normal size and shape for a girl of her age – without a single telltale scar from the original surgery.
Kirsty was born with a rare heart condition, which is frequently fatal within the first three months of life. The defect meant that her left coronary artery, which carries blood to the heart muscle, was connected to the pulmonary artery instead of the aorta.
As a result, the organ was starved of oxygen and became enlarged. Kirsty had numerous heart attacks as a baby and her prospects seemed bleak.
As her condition became critical, Professor Westaby was called upon to carry out corrective surgery at the John Radcliffe Hospital, Oxford.
But Kirsty was linked up to a heart lung bypass machine for the surgery – and when the surgical team attempted to get the heart to take over once again, they found it was so badly damaged that it was unable to pump blood again.
'We felt there was no hope at all,' Professor Westaby told Sky News.
A message was even sent to Kirsty's parents to warn them 'it was not going well'.
'She was essentially dead and was only resurrected by what I regarded at the time as a completely bizarre operation,' added Professor Westaby.
However, the surgeon had a hunch that reducing the size of Kirsty's heart would ease the pressure on the muscle, allowing it to contract properly.
And using scissors, he removed a large section of the muscle wall, stitched it back together, and hoped for the best.
'I have to confess I never thought it would work. It was an awful lot smaller.' But the baby's heart began beating again.
Today, Kirsty, of Cirencester, Gloucestershire, is a sporty tenyear- old who plays rugby at school. 'Her recovery is miraculous,' said Professor Westaby.
Her mother, Becky, 38, said: 'She's such a sporty girl. It's hard to imagine she was ill sometimes.' Recalling her first sight of Kirsty after the operation, she added: 'There she was, my tiny baby, with tubes everywhere. They said she'd take a step forward and a step back. But I could tell by looking at her that she would keep going.
It's amazing what she has overcome. 'She's such a brave little girl but and has never let her condition affect her life at all. I think that has been behind her recovery – she doesn't think about it.'
Kirsty's father Wayne, a computer- software salesman, said: 'It was a dark day when she went in the operating theatre. It's unbelievable. She has a normal life like any other girl.'
Professor Westaby said the results of a recent MRI scan of Kirsty's heart were 'fascinating' because of the extent the heart has healed itself. 'An adult heart wouldn't do that.'
As for Kirsty, she has refused to let her early problems shape her life. 'I don't want to be different to anyone else just because I've had a heart operation,' she said.