Parents, hospital staff and MPs joined a protest rally and march in Leeds against the closure of the unit at the city’s infirmary.
Hundreds of patients from large swathes of the region face journeys of as long as three hours in some cases to Newcastle for life-saving surgery after the decision by NHS chiefs.
Demonstrators held banners and signs reading “SOS Save Our Surgery” and “Don’t Break My Heart” as they gathered before a march around the city centre.
MPs Stuart Andrew, Hilary Benn, Greg Mulholland and Ed Balls were among those taking part in the march.
A group of nurses joined the speaker on the steps with banners, which read: “Proud to deliver gold standard care” and “467 years of combined cardiac nursing experience lost”.
One nurse, addressing the crowd, described the proposed closure as a “fundamentally flawed decision which has ignored the voices of Yorkshire families”.
The demonstrators chanted “we shall not be moved” as they marched around the city and back into Millennium Square.
Parent Lois Brown, of Skipton, whose daughter Amelie stopped breathing when she collapsed with a heart condition and had to be rushed to the infirmary, addressed the crowd before the march.
Cheers rang out as she said: “I think it’s vital to keep this unit in Leeds. I’m loyal to this unit, I’m loyal to these fantastic staff, who I love. But I’m loyal to my child.
“We want the best service, but we don’t want it at the cost of our children’s lives and our grandchildren’s lives. We shall not be moved and we will keep it open.”
Another mother, Sally Boocock, of Cracoe, near Skipton, whose daughter Ruby has a serious heart complaint, told the crowds: “We may have lost the first battle, but we have not lost the war. We will keep on fighting.”
Sharon Cheng, director of the Leeds-based Children’s Heart Surgery Fund charity, said around 3,000 people had taken part in the demonstration.
She said: “I’m overwhelmed basically. We’ve had people join us who are not connected to the unit, which speaks volumes.
“We understand why larger, fewer centres would make sense but you have to put them where the population is.”
Pudsey Tory MP Stuart Andrew, said: “There’s a huge strength of feeling and I hope common sense will prevail.
“Everybody is determined to do what they can.
“We are absolutely sure that parents won’t travel to Newcastle. They will go to Liverpool or Birmingham instead and Newcastle won’t reach the required 400 operations a year.”
Leeds Central MP Labour’s Hilary Benn said: “We won’t rest until the Leeds children’s heart unit is reprieved and goes on doing what it has been doing for so long to provide the best quality service to the people of Leeds and of the region.”