Question: I understand that defibrillators work by giving you an electric shock when a heart goes out of rhythm. Do these shocks hurt?
Answer: A defibrillator shock, if you're wide awake, will indeed hurt. The description is that it's like being kicked by a mule in the chest. It's a sudden jolt.
Now, most of the time when a defibrillator shock occurs in an appropriate session, whether it's an external shock through an AED or an internal shock through an implantable cardioverter defibrillator or ICD, if the patient is already unconscious, they won't ever feel or remember the shock.
At times, an appropriate shock from an ICD and certainly inappropriate shock from an ICD will occur when the patient is indeed awake and at that point, it would be uncomfortable -- not terribly painful, but uncomfortable.