[tialaramex]

Maybe, as it says, "The survival rate is about 10%" even though large numbers of people experience cardiac arrest in a clinical setting where they had defibrillators for years. Lots of Cardiac Arrest incidents aren't survivable, if your heart actually stopped they can't do anything about that. But without measuring (the first step the AED takes) you can't tell whether the heart is stopped or merely stuck twitching and not pumping blood, in the latter case the defibrillator may fix that, hence the name.