Update:
After wearing a Halter Monitor for 24 hours, my Cardiologist said I am having extra beats coming out of the top and bottom of my heart, evidently from the Mexiletine. I didn't notice anything before starting it. The ECG was normal.

I hope I'm saying this right. The beats are coming in twos, so while it's not normal, it's OK as long as we don't increase the dosage, and if the symptoms get worse, we stop. The Mexiletine has taken care of about 80- 90% of the new "zaps" to my feet, so I would like to stay on it, but not if it means damaging my heart. The cardiologist said at this point I am safe.

Hugs,
Jan