Health Vibes to Jeanne
I understand what you are going through because I have that same problem (oddly enough so does my mother in law)
It landed me in the hospital a couple of times where I had to be given an intravenous to slow it down, but most time it passes on its own the important thing is to try not to stress out when it happens because that usually causes the episode to extend
The hearts beats so fast and hard that my heart can be seen to be beating through my clothes a la a Tom and Jerry cartoon
I have learned to avoid any "energy" drinks, espresso drinks , anything that is highly caffeinated including many over the counter medications for allergies, cold relief etc
Also lying down in a darkened room and breathing deeply and slowly often helps to shorten the episode