Daniel, left, Grzegorz, Eliza, and Aneta Szymczak at their Christchurch home - one they will soon have to give up as visa problems for Eliza mean they will all have to return to Poland.

A Polish family in Christchurch will be forced to leave their adopted home after their six-year-old's visa renewal was rejected on medical grounds.

Graphic artist Aneta Szymczak said she felt cheated by immigration officials, who had allowed her, husband Grzegorz and their two children to start a new life in New Zealand two years ago knowing then the full medical condition of their youngest daughter, Eliza, 6.

Despite having six months to go on their current visas, the Szymczaks applied early in February for a second work to residence visa for themselves and students visas for the children as they prepared to seek permanent residence status in New Zealand.

Visas for the adults and son Daniel, 7, were quickly granted, but after months of delays they were shocked to discover Eliza could not remain.

Immigration New Zealand decided her pre-existing medical condition – Fallot syndrome – meant she was not of an acceptable standard of health and would likely to impose significant demands and costs on the country's health system in the future.

Tetralogy of Fallot (TOF) is a rare congenital heart defect occurring on average in five out of every 10,000 babies born.

Aneta Szymczak said recent medical tests showed Eliza's medical condition had not changed.

"Eliza's heart looks normal, and she is doing very well."

The Szymczaks conceded further corrective cardiac surgery may be needed in the future, but said the timeframe could not be predicted.

The defect appears as either a hole between the heart's two lower chambers, or the muscle on the right ventricle can be thicker than usual restricting flow, or as a narrowing of the pulmonary valve or as an arterial defect.

TOF changes the normal flow of blood through the heart by letting oxygen-rich blood from the left ventricle of the heart mix with oxygen-poor blood from the right ventricle.

Eliza underwent two corrective surgeries in Poland shortly after her birth in 2012 to correct a faulty pulmonary heart valve.

Grzegorz Szymczak, a software engineer, said that when he saw a job advertised online three years ago the couple quickly applied, seeking a new life in New Zealand.

"We filled out all the forms truthfully and gave them all the details on Eliza's condition."

Their visas were granted but it took months for Eliza's to come through as her medical documents had to be sent to New Zealand for review before approval was finally granted.

"We almost missed out on the job because it took so long for Eliza's approval to come through."

"So, this time we decided to start applying earlier for a second work to residence visa because we knew it would take longer."

INZ, on advice from specialists at the Canterbury District Health Board and Starship hospital, have now decided further corrective surgery may be required. Even though they do not define when, Eliza was still deemed a risk to the New Zealand health system.

Grzegorz Szymczak said Eliza was tested every year and specialists had recently told them she was as good as she could be.

"But now we have to go back to Poland because while we all can stay, she cannot."

INZ said no decision had been made on Eliza's application. It wrote to the family on May 17 inviting them to provide any further comment and submit any additional evidence, but had not heard back.

The Szymczaks believed they had provided all the information they could.

It did not directly respond when asked if the rules had changed since Eliza arrived in the country, saying every application was "assessed on its own individual merit and against current immigration instructions".