When I start to twitch (it happens some months and not others) it's usually in my leg muscles (a particular place in my thigh and my upper calf) or my mid-chest area right at the bottom of my sternum, slightly to the right, kind of in the muscle above my lower rib cage. Almost near my diaphragm. It feels really strange, and has been really bad during some months (happening all night long for instance).
On you, does it affect the heart beat/rate itself? Do you think it's actually the heart muscle, or a muscle near it?
Earlier in my recovery (in my first 2 years), the twitching was more often in my right eyelid and near my mouth. I rarely have that now.