You probably already know this, but for the benefit of others: it is very possible to kill yourself if you do this wrong. The vagus nerve (or its mirror on the opposite side of your face, I forget, it's been a while since I worked on this and I've never particularly wanted to revisit it) is involved in pacing your heart. Screw it up and you can end up very dead of cardiac arrest.

So be careful trying this stuff at home!