I have had the following done by a cardiologist 2 ekgs, ultrasound of my heart and another treadmill test. Although my heart is weaker, there apparently isn't anything that they can find. I may have POTS. But they are hoping that it will go away with time and for me just to deal with the sudden spike in BP and HR.I have improved some, but still deal with the scary feelings off and on. I know Mirena did this!