Cardioversion is used in emergency situations to correct a rapid abnormal rhythm associated with faintness, low blood pressure, chest pain, difficulty breathing, or loss of consciousness.
Interesting use of electric shock on the heart. I forgot to post the link...
http://www.hrspatients.org/patients/treatments/cardioversion.asp
Perfect, now taser victims can also sue police for practicing medicine without license :-)
Indeed it is known how defibrillators work. However in most cases they are operated by medical personnel, and only when they are needed, and the paddles are placed exactly where they should be. There are automatic defibrillators now, to be used by anyone, but they are fairly complicated, contain an internal ECG, and their program has the final say on whether to administer shock or not. It won't do a thing to a healthy person, for example - or to a sick person whose condition is not treatable this way.
Tasers, on the other hand, are used indiscriminately by people with little training in medicine. Their purpose is not to help but to hurt. The shock area is random (depends on where the needles will hit) and the shooter can apply multiple shocks. I am an EE, and in the university we were taught how electric currents affect people. Heart damage is the most dangerous scenario, that's why you are supposed to work with one hand only, and stand on an insulating pad. Wikipedia says this:
The minimum current a human can feel is thought to be about 1 milliampere (mA). The current may cause tissue damage or fibrillation if it is sufficiently high.