It is in fact very possible to do this, a fact I found surprising. In Asimov’s biography he described having gone about his affairs for at least several weeks after a major heart attack. He thought it was indigestion I think.

This is, of course, a very bad thing for the health outcome of a patient, and it is far preferable that they get early treatment. But it is certainly quite possible to live after a heart attack.

It’s in fact a common enough phenomenon that Harvard writes articles about it: https://www.health.harvard.edu/heart-attack/when-heart-attac...