In Iron Man, Tony Stark uses a minified version of the ARC Reactor in his chest to keep shrapnels out of his hearth and other organs.

When the ARC Reactor is removed (for changing palladium, stolen by Obadiah, damaged, etc) Tony starts agonizing, but why he didn't die immediately?

I think the blood would carry the shrapnels in a really high speed so Tony would have his organs damaged almost immediately, and even after replacing the ARC Reactor, it would be too late and his organs were already damaged.

Also, when Tony removes the ARC Reactor, why aren't the shrapnels attached to it? The shrapnels are made from metal, and the ARC Reactor is a magnet, it should push the shrapnels...