Originally Posted by samsnee
I'm not a doctor, but I'm pretty sure holding your breath doesn't stop your heart from beating.
No, it doesn't. Like I said earlier, an EMT with a stethoscope or (an EKG machine) would have caught it. They would at least have tried to take Coulson's blood pressure, and even with the massive blood loss he would have had one if his heart was still beating.
This would be harder to swallow than an LMD or zombification, if holding his breath is the explanation Whedon used. That's why I don't buy the spoiler. It's just too amateurish.
By the way, Clark Gregg posted this on Twitter:
True or false, spoilers suck.
He could have been referring to this or Iron Man 3
, but it's equally valid.