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The most important cardiac arrest interventions for patients in VF or VT are early chest compressions and defibrillation. Although 70‐80% of VF can be successfully converted to a perfusing rhythm if shocked within 3 minutes of VF onset, this success rate deteriorates rapidly with each additional minute [43]. Survival decreases 7‐10% for each minute that passes before defibrillation (Figure 12.3) [36].

AEDs provide lay bystanders with the ability to deliver rescue shocks. These devices were first used clinically in 1979 to recognize and deliver rescue shocks for VF and rapid VT [44]. AEDs are automated and simple to use, with visual and audible instructions for operating the defibrillator and initiating CPR. They are relatively inexpensive and extremely safe; modern AEDs do not allow delivery of inappropriate shocks [45]. Most are equipped with memory modules that can record the entire resuscitation event, including continuous ECG and audio recording.

Figure 12.3 Relation of collapse to CPR and defibrillation to survival: simplified model. Graphical representation of simplified (includes collapse to CPR and collapse to defibrillation only) predictive model of survival after witnessed, out‐of‐hospital cardiac arrest due to VF. Each curve represents change in probability of survival as delay (minutes) to defibrillation increases for a given collapse‐to‐CPR interval (minutes).

Source: Valenzuela TD. Circulation. 1997; 96:3308–13. Reproduced with permission of Lippincott, Williams and Wilkins.

Defibrillators with CPR feedback use accelerometers embedded within chest defibrillation pads to measure depth and rate of compressions, or use variations in chest impedance to reflect chest wall movements [46, 47]. These devices are able to give verbal as well as visual prompts to cue the rescuer to speed up, slow down, or increase the depth of compressions or ventilations [48]. Such devices have been shown to improve the quality of out‐of‐hospital as well as in‐hospital CPR [48, 49].

Many AED models are now available, ranging in sophistication and ruggedness. Some models are designed for minimally trained lay bystanders and are available for consumer purchase without a physician prescription, depending on applicable laws.

There is strong scientific evidence confirming the effectiveness of early first responder, bystander, and public‐access defibrillation. A trial that trained security personnel in casinos to recognize OHCA, start CPR, and use on‐site AEDs achieved 53% survival from VF. Among patients shocked within 3 minutes, survival was 74% [24]. AEDs have also been successfully used on commercial aircraft and in airports [50]. In the multi‐center PAD trial, 993 high‐risk locations were randomized to deploy or not deploy on‐site AEDs. A response plan with identification and training of on‐site responders was implemented at all sites. Survival was double at AED sites compared to non‐AED sites [23]. Other reports also describe successful public‐access defibrillation programs [51].

In Japan, public‐access defibrillators became rapidly available starting in 2004 [52, 53]. The cumulative number of public‐access defibrillators (excluding medical facilities and EMS institutions) increased from 9,906 in 2005 to 297,095 in 2011 [54]. From 2005 to 2007, the proportion of bystander‐witnessed VF/VT arrest victims who received public‐access defibrillation increased from 1.2% (45/3841) to 6.2% (274/4402) [52]. The latest data show that over 40% of cardiac arrests in public places like train stations and sports facilities received shocks with public‐access defibrillators.

The observation that a majority of OHCA events occur in residential settings raised interest in home deployment of AEDs. This concept was evaluated in a large, multicenter, international trial of anterior wall myocardial infarction survivors who were not candidates for implantable cardiac defibrillators [55]. A related innovation is the wearable cardioverter‐defibrillator, which combines a long‐term ECG monitoring system with an external automatic defibrillator [56].

Locations at high risk can be identified using public health surveillance tools such as registries that collect standardized data about OHCA. Cardiac arrest locations can be analyzed using geographic information systems and spatial epidemiology methods to identify and target high‐risk neighborhoods within a community [57, 58]. These should have emergency preparedness and response plans that include AED deployment [59–61]. Such areas may include airports, fitness centers, large workplaces, arenas and convention centers, and even jails. AED deployment and response plans should include registration with dispatch centers, development of a notification system to alert on‐site responders, selection and training of responders, and deployment of appropriate AED and other rescue equipment. Equipment maintenance, annual response plan review, and quality improvement incident reviews are essential components of an effective public‐access defibrillation program. Smartphone apps are also available which can show the location of the nearest AED during an emergency. These can be integrated into local response systems.

There is an important opportunity for local EMS agencies and medical directors to assist public and private sites with implementing public‐access defibrillation programs. Several web sites and publications provide detailed suggestions for public‐access defibrillation program development [62–65].