hello! One of the most prominent signs of anxiety and panic attacks is accelerated heart rate. Like the other doctors that have seen you, i also think that you have anxiety and the fast heart rate is its symptom. It's very common that these patient seek treatment for chest pain or
heart attack. Panic attacks can be triggered by different stimuli, or they can be also unexpected which are unrelated to such triggers. Symptoms of a panick attack are
palpitation, accelerated heart rate, sweating,
shortness of breath,
chest tightness and discomfort, nausea, dizziness, fainting, numbness and
tingling sensation especially in the extremities, fear of loosing control, fera of dying. The persons that experience repeated panic attacks suffer also from the fear that another attack may happen.
In my opinion you should consult a doctor to start the appropriate treatment.
I hope i have been of help.