Beating too fast? If a regular ekg has been normal a 24 hr remote heart monitor is often ordered to see if there are abnormalities in the heart rhythm and rate that may not have been found on a one time ekg which covers a very short period of time and may miss the abnormality. If that is normal it may indicate your heart beating scares you & may very well be panic attacks. A psychiatric evaluation is in order then.
Palpitations. Subjective feeling of heart beating could be due to anxiety. One would feel heart beating when blood pumping is higher per beat like when running or exerting. In anxiety however there is a subjective sense of heart beat even though volume per beat is normal. Talk to your pcp, he may do tests to rule out medical causes before diagnosing anxiety.