AEDs are primarily designed to treat two conditions :
These are conditions wherein the heart is electrically ‘alive’ but stuck in a dysfunctional pattern that does not allow it to efficiently pump and circulate blood throughout the body. In a V-tach condition, the heart beats too fast to effectively pump the blood. V-tach most often leads to V-fib. In a V-fib condition, the electrical activity of the heart goes haywire. This does not allow the ventricle to pump blood throughout the body. The fibrillation in the heart decreases over time, until it eventually reaches asystole (flat-line condition)
Once the heart flat lines, the AED device is unable to treat the patient as this would lead to a negative clinical outcome. This makes it imperative for first responders to perform CPR or CCR on the patient until the one of the two conditions treatable by AEDs is established and the device can be used successfully.