Your skin has too much resistance for this; the current would not penetrate the epidermis. When you check a battery with your tongue the shock is from the short across the conducting outer wet, salty surface. If you used conducting needles through the dermis on both terminals and there was a path through the heart it might approach the threshold to trigger an arrhythmia (~50-100 mA I think), but very unlikely.
I saw this on an old Navy safety film.
You are correct - 100 mA can stop your heart and kill you. But most deaths are not caused from the shock - they result from the impact with the ground when you fall off the ladder.
Soaking wet, with perspiration as electrolyte, has been implicated in some accidents attributed as low voltage electrocution. The lowest threshold for concern is 5mA.
Funny thing is that TENS medical therapy units often pulse well above this threshold.