AED除颤器is a treatment for life-threatening心律不齐, specifically心室颤动（VF）和non-perfusing ventricular tachycardia(VT).^[1][2]除颤器提供了一剂电流（通常称为反击）心。这个depolarizes大量心muscle, ending the dysrhythmia. Subsequently, the body’s天然起搏器在里面Sinotrial节点心脏的内心能够重新建立正常的窦性心律。^[3]

与除颤相反，同步电气cardioversionis an electrical shock delivered in synchrony to the心脏周期。尽管该人可能仍然重病，但心脏抗辩通常旨在结束灌注不良的心律不齐, such assupraventricular tachycardia。^[1][2]

除颤器可以是外部，透性或植入(可植入的心脏逆变器除颤器), depending on the type of device used or needed.^[4]一些外部单元，称为automated external defibrillators(AEDs), automate the diagnosis of treatable rhythms, meaning that lay responders or bystanders are able to use them successfully with little or no training.

Defibrillation is often an important step incardiopulmonary resuscitation(CPR).^[5][6]CPR is an algorithm-based intervention aimed to restore cardiac and pulmonary function.^[5]Defibrillation is indicated only in certain types of心律不齐, specifically心室颤动（VF）和pulseless ventricular tachycardia。^[1][2]If the heart has completely stopped, as inasystole或者pulseless electrical activity (PEA), defibrillation is not indicated. Defibrillation is also not indicated if the patient is conscious or has a pulse. Improperly given electrical shocks can cause dangerous dysrhythmias, such as心室颤动。^[1]

Survival rates for out-of-hospital cardiac arrests are poor, often less than 10%.^[7]Outcome for in-hospital cardiac arrests are higher at 20%.^[7]Within the group of people presenting with cardiac arrest, the specific cardiac rhythm can significantly impact survival rates. Compared to people presenting with a non-shockable rhythm (such as asystole or PEA), people with a shockable rhythm (such as VF or pulseless ventricular tachycardia) have improved survival rates, ranging between 21-50%.