Hello and thank you for using HCM. I carefully read your question and I understand your concern. I will give you my opinion about this. You explain about fast, racing heart beats and feeling dizzy, light head. My opinion as a cardiologist is that this symptoms are related with some heart rhythm issues. It might be possible that the doctors do not find anything, because you are under normal rhythm when you meat the doctors. This rhythm problem might be different.The most important one is atrial fibrillation. This is an arrhythmia when the heart runs in a chaotic way. This is why you might feel your heart running fast. Also it doesn t wok properly, it doesn t feel normally and for this reason the person might experience dizziness, lightheaded. This rhythm issue might happen once a wile, it comes and go, and so it is difficult to catch it. So, my opinion is that you should do some examinations, where the most important one is holter rhythm monitoring for 48 h. Taking the monitor for 48 h rises the possibility to chatch the rhythm problem if it is any. I don t know if you already did it, but you may repeat it again to rise the possibility to catch something. Also, I will recommend a cardiac echo, a blood analyze to exclude anemia or thyroid gland problems that cause this kind of problems sometimes. If all this examinations result normal,than you should not worry.Only after this we might say that every thing is alright, its just stress. Hope I was helpful. Wish you good health. Best regards.