Just two weeks before she died, Zoe Chambers and her family were celebrating the new life a heart transplant had given her.

On June 28, the first anniversary of the life-saving surgery, two-year-old Zoe was partying with family and friends after taking her first steps, reducing her medication and planning an appearance as the youngest entrant at the British Transplant Games.

But on Saturday - 12 July, 2008 - tragedy struck.

It is understood that Zoe fell ill at the family home in west Hull.

She was taken to Hull Royal Infirmary's paediatric accident and emergency department, where doctors battled to save her life.

But, despite their best efforts, Zoe passed away.

Today, as Zoe's parents, Julie and Rob, both 34, grieve with Zoe's six-year-old brother Dylan at home, tributes have poured in for the youngster who in the past year amazed doctors with the speed of her recovery.

Dr Richard Kirk, the transplant cardiologist at Newcastle Freeman Hospital, where Zoe spent many months before and after surgery, said staff were in shock.

He said: "We accommodate half the transplant children in the country and they don't come any more special than Zoe. Her death is a terrible tragedy.

"All the staff at the hospital who helped Zoe when she was here are devastated.

"Zoe spent a long time in our care, from first being admitted through to the after-care she received, and we get very close to the children, so it's utterly devastating when they suffer."

Before getting her new heart, Zoe suffered six heart attacks and survived for 100 days attached to a Berlin Heart – a £100,000 piece of equipment that kept her alive.

The need for a new heart became so desperate Zoe was fast-tracked to the top of the European transplant list and at one point doctors gave her 24 hours to live.

After her transplant Zoe returned home and had been going from strength to strength.

She began eating proper food, enabling her family to remove a gastric nasal tube, and on Mother's Day this year she took her first steps.

Dr Kirk said he had been treating Zoe for about 18 months and the circumstances surrounding her sudden death were uncommon.

He said: "What happened to Zoe is so unfortunate and extremely uncommon.

"To die after a year following the huge steps forward she had taken is unheard of in our experience.

"She was doing so well. We expected her to take much more time to recover, but she didn't and that was testament to her strength."

Zoe had become an icon for organ donation nationally.

A spokesman for UK Transplant said: "We are deeply saddened to hear of Zoe's sudden death and our thoughts are with her family.

"Zoe and her parents have played a significant role in encouraging more of us to join the NHS Organ Donor Register."