Sit or lie down. Take some slow, deep breaths. Follow your doctor's instructions, which often means taking an extra dose of your heart-slowing medication. If you develop chest pain or shortness of breath, call for emergent advice or have someone drive you to an emergency department now.
If you have no other symptoms, but your heart rate is still fast, call your doctor for advice. He or she may suggest taking an extra dose of your heart-slowing medication.
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