How do you bear down as if in a bowel movement to calm heart rate?

I suffer from rapid heart rate. I can be sitting and my heart goes from 69 bpm to 150 bpm while resting. The Emergency Room Doctors said to me when I was over 189 bpm "bare down as if you were having a bowel movement" and it does work most of the time. If you have a rapid heartbeat for over an hour get to the ER. However, never take medical advice from anyone other than your own Physician.