A diagram showing the chain of survival. Conditions that the device treats An<unk>  is used in cases of life-threatening cardiac arrhythmias which lead to sudden cardiac arrest, which is not the same as a heart attack. The rhythms that the device will treat are usually limited to: # Pulseless Ventricular tachycardia (shortened to VT or V-Tach) # Ventricular fibrillation (shortened to VF or V-Fib) In each of these two types of shockable cardiac arrhythmia, the heart is electrically active, but in a dysfunctional pattern that does not allow it to pump and circulate blood. In ventricular tachycardia, the heart beats too fast to effectively pump blood. Ultimately, ventricular tachycardia leads to ventricular fibrillation. In ventricular fibrillation, the electrical activity of the heart becomes chaotic, preventing the ventricle from effectively pumping blood. The fibrillation in the heart decreases over time, and will eventually reach asystole.<unk> s, like all defibrillators, are not designed to shock asystole ('flat line' patterns) as this will not have a positive clinical outcome. The asystolic patient only has a chance of survival if, through a combination of CPR and cardiac stimulant drugs, one of the shockable rhythms can be established, which makes it imperative for CPR to be carried out prior to the arrival of a defibrillator. Effect of delayed treatment Uncorrected, these cardiac conditions (ventricular tachycardia, ventricular fibrillation, asystole) rapidly lead to irreversible brain damage and death, once cardiac arrest takes place. After approximately three to five minutes in cardiac arrest, irreversible brain/tissue damage may begin to occur. For every minute that a person in cardiac arrest goes without being successfully treated (by defibrillation), the chance of survival decreases by 7 percent per minute in the first 3 minutes, and decreases by 10 percent per minute as time advances beyond ~3 minutes. Requirements for use Defibrillator training kit<unk> s are designed to be used by laypersons who ideally should have received<unk>  training. However, sixth-grade students have been reported to begin defibrillation within 90 seconds, as opposed to a trained operator beginning within 67 seconds. This is in contrast to more sophisticated manual and semi-automatic defibrillators used by health professionals, which can act as a pacemaker if the heart rate is too slow (bradycardia) and perform other functions which require a skilled operator able to read electrocardiograms. Bras with a metal underwire and piercings on the torso must be removed before using the<unk>  on someone to avoid interference. American television show MythBusters found evidence that use of a defibrillator on a woman wearing an underwire bra can lead to arcing or fire but only in unusual and unlikely circumstances. In a study analyzing the effects of having<unk> s immediately present during Chicago's Heart Start program over a two-year period, of 22 individuals, 18 were in a cardiac arrhythmia which<unk> s can treat. Of these 18, 11 survived. Of these 11 patients, 6 were treated by bystanders with absolutely no previous training in<unk>  use.
Automated external defibrillator
Transcutaneous pacing
Transvenous pacing
Cardiac pacemaker
Defibrillation
Pacing 
Biological pacemaker
Implantable cardioverter-defibrillator