You're asking a speculative question about a hypothetical medical experiment - and one for which it would be hard to obtain ethical approval, at that. Rather than messing with heart function, wouldn't it be simpler to use anoxia/asphyxiation instead, since that's the major physiological correlate resulting from cessation of heartbeat?
People do not (edit: not necessarily, at least) lose consciousness immediately during a heart attack. On the other hand, I have fallen asleep straight after smoking some DMT...
“There is a way of manipulating matter and energy so as to produce what modern scientists call 'a field of force'. The field acts on the observer and puts him in a privileged position vis-à-vis the universe. From this position he has access to the realities which are ordinarily hidden from us by time and space, matter and energy. This is what we call the Great Work."
― Jacques Bergier, quoting Fulcanelli