What Causes Chest Discomfort After Suffering From Anaphylaxis?

My daughter, 16yo, felt that she was having an anaphylactic reaction and used her epi pen. She was having trouble breathing, hands shaking, going numb, and feeling of impending doom. After using the epi pen she had lost consciousness and was in respiratory distress according to the ambulance. At the ER they did blood tests. Her Potassium was LL at 2.6. She is still tachycardic today, Pulse of 108. It has been 2 days. She is also reporting some chest discomfort and generally does not feel very well. Should we be concerned about this?