I've attended dozens of deaths over the years, and many hours of medical training.

Yes, some folks do appear to die peacefully. And some folks don't sleep through it. And some folks will die through particularly ugly and unpleasant processes.

In some specific cases, we do know that the death did not entail any struggling or other manifestations of discomfort.

And you are quite wrong about your concept of how a heart attack can present itself. Some are quite silent. Some - in older men and particularly in older females and reportedly due to differences in and degradations in the cardiac innervation - can be undiagnosed or misdiagnosed or missed - and sometimes these cardiac problems might only trigger a so-called syncopal episode. The person "zones out" for a little while, or "faints". This due to a transient drop in blood pressure.

In cases I'm very familiar with, the person simply stopped talking to me, and appeared to doze off, and the cardiac monitor went into alert.

In others, I've encountered a number of cases where the only evidence of a heart attack was in the cardiac enzymes test, or due to specific artifacts seen in subsequent cardiac monitoring.

My father, who passed last winter, showed signs of dying peacefully while awake. He was lying back on his bed, whith his hands behind his head, like he was thinking about something when they found him. There was no sign of discomfort or struggle- only, really, curiosity (but I am probably assuming too much with that).

The current theory goes that dying peacefully in sleep is possible. Elizabeth Simpson of the Virginian-Pilot explored this question further and a nice little article summarizing the excerpts from the AHCJ discussion can be found at: http://www.healthjournalism.org/blog/2011/07/reporter-explor...

My question is, given the existence of sleep paralysis which is both terrifying and plausibly able to leave "no evidence of thrashing about", if many people died "peacefully" but also awake and very scared.

As a sufferer of sleep paralysis, I would think it almost impossible that sleep paralysis itself could persist through dying painfully, since pain or other external stimuli (or passage of time, usually less than a minute) will generally kick you out of it.

That doesn't preclude the existence of some other paralysis mechanism, but I am not aware of any, so I think it's just wild speculation.

As I'm sure you've guessed, it's sometimes an emotional defense mechanism on the part of the survivors. Don't know anyone who wants to envision their loved one's last moments in agony, even if true.

Maybe it wasn't a heart attack.