So what about a simple case of Gastro? Surely they can't permanently remove your medical for that?
They can, and almost certainly will. The point is that anything that causes you to lose consciousness that suddenly is a no-no. I've had gastro before and the onset took hours, not minutes or seconds, and I never lost consciousness - although the effects can be debilitating.
The medical people won't (and shouldn't) take the risk of a re-ocurrance, simple as that.