Greetings. Thank you for your question and welcome to HCM. I understand your concern. My opinion is that it is probably nothing to worry about. However, facing a tachycardia at your age, can come from various reasons, which probably are physiological, like the psychological stress you went through during your electrocardiogram (EKG). Although, I suppose, your doctor s suspicion was minimal, my opinion is that some doctors find it reasonable (which is not wrong) to an echocardiogram, just to be in the safe area , and not miss anything pathological that could be the origin of that tachycardia. Two-dimensional echocardiogram is an exam which allow us to precisely evaluate the size and the function, also the totality and integrity of heart structures. By heart structures I refer to any structural problem that the heart might have, like problems from birth or any damage in the structure of heart valves. These are suspicions that we, cardiologists, might have and seek, in a 21 year old individual. I would continue to state that my opinion is that there is nothing to worry about. Judging from the data provided by the symptoms which led you to do an EKG, in the first place, and the EKG itself, if you were my patient, maybe I would have found it appropriate, also, to request a 2D echocardiogram. I hope this answers your query. Take care. Best regards, Dr. Meriton