Mary
Sounds like you're having a "panic attack" during these "episodes". I would consult a psychiatrist to get further evaluated and get possible medication that will help. I suffer from panick attacks from time to time and my heart pounds the exact same way. Please don't panick from these attacks (hence the name) as most people stop doing all together whatever they were doing during these attacks because they are afraid of either passing out or dying (you will NOT die from a panick attack). Best thing to do is to just "ride them out". If you are driving, try to pull over until the attack subsides (for safety). Good luck! :)