Do defibrillators work?

Oh yes. Defibrillators are extraordinarily effective devices for the treatment of what would otherwise be fatal lower chamber heart rhythms. That said, they must be used in an extremely timely fashion or their benefits will not prevent irreversible damage from the lack of blood flow seen in these dangerous rhythms.
Yes . All the time. Between the defibrillator & the rest of the medical team, we saved 3 lives in 1 week at my hospital & 2 of these occurred outside the hospital.

Related Questions

Do defibrillators work in asystole?

Defibrillator. Paramedics may attach monitor and defibrillator leads as a routine. But defibrillation is not the treatment for asystole. Read more...
No. Defibrillators work to disrupt an irregular, rapid, pathological heart beat. They don't "jump start" a heart that is not beating. Read more...