Hello and thank you for using HCM.
I carefully read you question and I understand your concern. You should not worry, i will explain you something and give you my opinion.
Fast
heart rate might have different causes. Sometimes simple emotional stress is the reason but as you explain you are not experiencing any stressed period.
Excessive coffee consumption or energy drinks might be other causes so you have to avoid them.
A lot of other pathology's might be responsible for fast heart rates like anemia,
hyperthyroidism or any cardiac anomaly.
It is important to know if you have regular fast beats or you experience this fast beating that might be irregular. Because in this case it might be an
arrhythmia not just a simple
sinus tachycardia.
So, if I was your treating doctor I will recommend some examination to better understand whats happening.
I will recommend an electrocardiogram, a cardiac echo to evaluate heart valves and structure, a holter rhythm monitoring during 24-48 h, a
stress test and a full blood analyze and your thyroid hormones.
Only after this we can judge what we are dealing with and how to treat it.
Hope I was Helpful.
Best regards.