my son is almost 15, for a few weeks while trying to go to bed he feels a heavy chest and symptoms like its hard to breathe, also notes his heart starts to race and feels like a shiver and sometimes gets really hot. no panic attacks, no stress , episodes last five min to half an hour. seem to be significant, sleeping up stairs and worried. family doc thought maybe it was panic but ordered an ekg . borderline qt so of course i panic. i have had a couple epidsodes of fainting so i did a tilt test. the nurse freaked, blood pressure and pulse went to 0 and she almost called for help. i was put on betablockers but the bp went so low i was a zombie, doc said very unlikely i would faint and not come out of it. very worried, could it be pre cordial prob, thyroid or something bigger?