I'm assuming the entire phrase would be "don't have a coronary occlusion" meaning "don't have a heart attack." I haven't been able to find anything useful regarding when or where it might have originated.
It has the same meaning as "Don't have a heart attack" and is used in a way to tell the other person to calm down and not get worked up.
The earliest examples I found are in snippets from 1982 books.
Immediate Release - Page 41 - William Mathewson - 1982 - Snippet view:
Marva Collins' Way - Page 135 - Marva Collins, Civia Tamarkin - 1982 - Snippet view:
Well, according to this google NGram, it seems to have appeared in 1960 and to have peaked in the early 70's. Perhaps it was popularized by a TV show of the time?