This is a good question. Although you were already evaluated by an emergency room physician, it is very important that you make a follow up appointment with your primary care doctor
as your symptoms are still occurring. It is difficult to know what all workup you had done in the ER but sometimes palpitations come and go so they might not have been present during your visit. There are many different causes of palpitations, from various arrhythmias to a fast heart rate (tachycardia) from drinking too much caffeine, An overactive thyroid can cause a fast heart rate so your doctor may order blood tests. You likely had an EKG done in the ER. Your doctor may order another one, or have you wear a heart monitor that constantly records your heart rhythms for a certain period of time. Anxiety
and panic attacks can also present as feeling like heart palpitations so your doctor will likely ask you questions about your mood, sleep, appetite, stress level, etc to see if this could be a cause of your symptoms. Depending on what your doctor discovers during your visit, he or she may refer you to a cardiologist
for further testing and evaluation. Your arm pain is likely unrelated but if you have any risk factors for a heart attack this could be a cause for concern. Again, please speak with your doctor.