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Automated external defibrillators

Thomas D Rea, MD, MPH
Mickey S Eisenberg, MD, PhD
Section Editor
Richard L Page, MD
Deputy Editor
Brian C Downey, MD, FACC


Sudden cardiac arrest (SCA) refers to the sudden cessation of cardiac activity with hemodynamic collapse and is most often due to sustained ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT). SCA is a major public health challenge, accounting for approximately 5 to 15 percent of total mortality in industrialized nations [1-3]. (See "Overview of sudden cardiac arrest and sudden cardiac death".)

Although survival from SCA remains generally poor, there is evidence from contemporary population-based registries that outcomes following out-of-hospital and in-hospital cardiac arrest have improved compared with historical experiences. However, there is substantial disparity across systems and hence opportunity to improve outcomes. Based on contemporary estimates of out-of-hospital cardiac arrest, approximately 10 percent of emergency medical services-treated patients in any cardiac rhythm and 30 percent of patients whose initial rhythm is VF survive to be discharged from the hospital [2,4-6]. Based on registry data from the United States and Great Britain, contemporary survival rates for in-hospital arrest are estimated at 20 percent for all rhythms and nearly 50 percent for patients with an initial rhythm of VF [7]. (See "Prognosis and outcomes following sudden cardiac arrest in adults".)

Although several interventions can improve the likelihood of VF resuscitation, the single most important is early delivery of an external electric shock to reset the cardiac rhythm and restore spontaneous circulation [8,9]. Early defibrillation is consistently associated with a greater likelihood of survival, which decreases by approximately 5 to 10 percent with each additional minute from collapse to defibrillation [8]. The potential benefit of early defibrillation is best illustrated by the outcomes following defibrillation at casinos; 74 percent with witnessed VF survived when a shock was delivered within three minutes from collapse [10]. A 2017 review of observational studies reported early defibrillation with automated external defibrillators (AEDs) is associated with an approximate doubling of survival when an AED was applied by lay first responders (survival of 53 percent) compared with professional personnel dispatched by emergency medical dispatch centers (survival of 29 percent) [11].

This topic will review the development, use, allocation, and efficacy of AEDs. Other aspects of electrical cardioversion and defibrillation are discussed separately, as are basic and advanced cardiovascular life support. (See "Basic principles and technique of electrical cardioversion and defibrillation" and "Cardioversion for specific arrhythmias" and "Basic life support (BLS) in adults" and "Advanced cardiac life support (ACLS) in adults" and "Supportive data for advanced cardiac life support in adults with sudden cardiac arrest".)


AED training — AEDs are designed to be straightforward to operate, and multiple studies have demonstrated that laypersons can operate them safely and effectively [12-16]. Nevertheless, they can be challenging to use, especially for the layperson [17-19].

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Literature review current through: Nov 2017. | This topic last updated: Sep 03, 2017.
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