That's why some "dead" people wake up in the morgue.
How often does that happen outside of the pages of the National Enquirer? Although, that is the reason caskets used to have a bell and rope attachment that stuck above the ground. Those paranoid that they would be buried alive would have an alarm bell.
Anyways, no patient that I have seen in the better part of two decades that has been asystole in two or more leads has ever waken up later after calling the code.