This is a disappointing response from your doctor. It seems that he or she is allowing patients to flood the ER at a time when there is low hospital capacity for a symptom the ER likely cannot help with. Rather, the doctor could provide a referral to a cardiologist, prescribe a beta blocker etc, Most POTS patients are told their tachycardia is typically not dangerous, but it depends on your particular issues. a cardiologist can run the tests and best advise you.