I would definitely not try it if there were heart issues going on either.
I've got hand issues :-), so I'm hesitating too :-).
I didn't want to try it again with the SEM-1652A because there is no way to make sure it's operating at 6V, which is what I understand it should be for hands. I briefly stuck 'em in (fingertips only) once, and felt a creeping/biting tingle which definitely caused me to extract them quickly.
That might have happened because I had broken skin on them right now, but I don't know that for sure..
I'll try it sooner or later, but only when I can guarantee it to be working at 6V.