When is a story 'new'?

I have a story that I wrote well over a year ago. It was published in an anthology. I have since taken that story and changed it considerably. It's still the same basic structure but the underlying theme and most of the key scenes are quite different. I'd like to submit this story for consideration in another journal but am unsure of when a repurposed story is or is not a 'reprint'. I feel like the story is 'new' but I don't want to misrepresent it. Any comments would be most helpful! Thx

Great idea. Should have thought of that. Thanks!