Hello and thank you for using HCM.I carefully read your question and I understand your concern.You shoud not worry . I ll try to explain you something and give you my opinion. Normal heart rhythm range between 50-100 beat for minute in normal conditions. If it exceed 100 beat for minute in a normal rhythm we call it sinus tachycardia. Sinus tachycardia might happen in different situations.Simple emotional stress or physical activiti might give fast heart beats and this is quite normal. Excessive coffee consumption, energy drinks might be responsible for sinus tachycardia. There are also some pathologyes like anemia, hyperthyroidism that might be the cause. So, in my opinion a frequency between 80 to 103 it is nothingbto worry about. The fact that you have already done an electrocardiogram and it is normal its a very good thing. But, if I was your treating doctor I will recommend some other examination like a cardiac echo to evaluate heart function and valves, a full blood analyze to exclude anemia , hyperthyroidism and of course a holter rhythm monitoring to see your frequency during day and night. After this we can better judge how to menage this frequencyes. Meanwhile avoid caffeine products and energy drinks becouse they exacerbate your high frequency. You can use erbs like camomile tea, it helps. Hole I was helpfull. Best regards.