Hi my son 13 yr old has irregular and very fast heartbeat since infancy i fear he has svt although nothing is shown on echo and ecg all his tests are clear.....i have a doctors appointment tomorrow.....need to ask if headaches are associated with svt too??? And what are the reason of a headache and how dangerous it is.... Could it lead to a stroke??? Desperately waiting for ur reply.... His heartbeat races while playing or running i even hear irregular beats while hes sleeping unfortunately none of the doctors have yet diagnosed it !!!! Thanks