Well, 'chest pain' can often be cardiac (relating to the heart) in nature - and anything that acutely affects the heart is a medical emergency, as if the heart stops, then so do you! As a consequence of Chest pain being potentially very serious, and because we see such a lot of it (about 1 in 3 jobs can be chest pain related) we are well trained in dealing with the various problems, and it has been drilled into us how serious chest pain can be. So while it is a medical emergency - it's not like someone who has had their leg chopped off (in which we would, quite possibly, panic just a tiny bit), but instead is an emergency that we are well trained/very experienced in dealing with. Doing three of four of these jobs every day, means that while it is an emergency, it is an 'easy', 'routine' emergency.