<s>[INST] ok, i think i was in about 7th grade, i was walking you know slow and easy down the hall and up the stairs, i dont know why but as soon as i sit down my heart started pounding and i could feel it like it was going to come out of my chest what could this be? [/INST] Hello! Thank you for asking on Chat Doctor! Regarding your concern, I would like to explain that your pounding heart feeling (that is palpitations), is among the most common heart related complains. It may be caused by just by an increased anxious state, is also a common finding during and after any physical exertions. These above options are almost physiological conditions, and you shouldn't worry about. But, we have to be sure no any other pathological reasons is responsible, first of all any arrhythmias. So, a careful physical exam, coupled with a resting ECG, and if suspicions are raised for a possible arrhythmia, a cardiac ultrasound and an ambulatory 24 to 48 hours ECG monitoring are necessary. Several blood tests (complete blood count to exclude a possible anemia; thyroid hormone levels to exclude a possible high abnormal thyroid function; PCR to exclude any inflammations, etc.). Hope to have been helpful! Greetings! </s>