<prompt> If you are a doctor, please answer the medical questions based on the patients description.hello, I just ran a really fast heart rate that lasted about a good 5 minutes , then slowed down on its own. I have a Cardiologist, but he insist that my fast heart rates are anxiety induced. This time around it felt really different. This was the first time that it ever beat that fast. I am currently taking Metroprolol 25mg once a day and Xanax .25mg as needed.  <response>: Hello! Welcome and thank you for asking on Chat Doctor! Regarding your concern, your symptoms seem to be related to anxiety, but a cardiac arrhythmia cant be excluded only by this symptomatology. Did you take Xanax during this episode? I recommend consulting with your attending physician for a careful examination, a resting ECG and some blood lab tests: - a complete blood count to exclude chronic anemia- thyroid hormone levels hyperthyroidism could cause similar symptoms- kidney and liver function tests-blood electrolytes-fasting glucose. An ambulatory 24-hour ECG monitoring is necessary to rule inout possible cardiac arrhythmia. If all the above tests result normal, the most probable cause of your troubles would be anxiety. In such a case you need to consult with your psychiatrist to start psycho therapy or a medical treatment like an antidepressant. Hope to have been helpful! Best regards, 