When i smoke too much i feel some pain in the chest, but for me it seems more an irritation due the smoke, because my heart keeps beating slowly as always.
I think i feel pain in the lungs, or in the part of the trachea which meets them... its hard to explain... but in my case im sure its due the smoke, cause when i cough the pain comes and goes, together with the phlegm i feel inside the lungs.