(Circulation. 2005;111:3336-3340.)
© 2005 American Heart Association, Inc.
AHA Science Advisory |
| Abstract |
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Key Words: AHA Science Advisory defibrillation heart arrest fibrillation cardiopulmonary resuscitation
| Introduction |
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To determine the effect of PAD programs on survival and other outcomes after SCA, the National Heart, Lung and Blood Institute (NHLBI), the AHA, and others funded a large prospective randomized trial. The results of this study were published recently in The New England Journal of Medicine.5 The purpose of the present statement is to highlight important findings of the Public Access Defibrillation (PAD) trial and summarize implications of these findings for healthcare providers, healthcare policy advocates, and the AHA training network.
| Background |
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250 000 people die in the United States each year from SCA outside the hospital setting.10 At the time of first heart rhythm analysis,
40% of SCA victims demonstrate ventricular fibrillation (VF), an abnormal heart rhythm that causes the heart to quiver so that it is unable to pump blood effectively.8 It is likely that an even higher proportion of people with SCA have VF at the time of collapse. Many people who experience sudden VF cardiac arrest can survive if bystanders act immediately. If VF is untreated, then cardiac standstill will develop, and successful resuscitation will be unlikely.11 The AHA has traditionally used 4 links in a chain to illustrate the important actions that can create a "chain of survival" for victims of VF SCA.12 These links are as follows:
Bystanders can now perform 3 of the links in this chain. Bystander recognition of the emergency and EMS activation are critical first steps in response to an SCA, ensuring that basic and advanced life support providers are dispatched to the site of the arrest. In most communities, the time interval from collapse to the arrival of EMS personnel is 7 to 8 minutes or longer. This means that the victim depends on the actions of bystanders and local rescuers to perform the first 2 or 3 links in the chain of survival during the first minutes after SCA.
Bystanders need to provide immediate CPR for victims of SCA. CPR provides blood flow to the heart and brain. In addition, CPR increases the likelihood that a shock delivered by a defibrillator will terminate the VF and that the heart will resume an effective rhythm after defibrillation. These effects of CPR appear to be particularly important if shock delivery does not occur for
4 minutes after collapse.13 Defibrillation does not "restart" the heart; defibrillation stops VF and allows the heart to resume a normal rhythm. In the first few minutes after defibrillation, the heart rhythm may be slow and the heart may not pump blood effectively. CPR may be needed for several minutes after defibrillation until adequate heart function resumes.14
Lay rescuers can use computerized devices called AEDs to deliver a shock to victims of VF cardiac arrest. The rescuer attaches the AED to the victim with adhesive pads or electrodes. The AED records and analyzes the victims ECG rhythm, informs the rescuer if a shock is needed, and provides voice and audio prompts to guide the rescuer through all steps of AED use. The AED computerized algorithms that are used to analyze the victims heart rhythm are accurate. AEDs will deliver a shock only when VF or its precursor, rapid ventricular tachycardia, is present and will not deliver a shock to a person with a normal heart rhythm.15
The success of the actions of rescuers at the scene of an SCA is time critical. Several studies have documented the effects of time to defibrillation and the effects of bystander CPR on survival from SCA. For every minute that passes between collapse and defibrillation, survival from witnessed VF SCA falls 7% to 10% if no CPR is provided.11 When bystander CPR is provided, the fall in survival is more gradual and averages 3% to 4% per minute from collapse to defibrillation.11,16 CPR can double11,16 or triple17 survival from witnessed SCA at any interval to defibrillation.
Lay rescuer AED programs may increase the number of SCA victims who receive bystander CPR and can reduce time to defibrillation. These programs require an organized and practiced response with rescuers trained and equipped to recognize emergencies, activate the EMS system, provide CPR, and provide defibrillation. Small studies of lay rescuer AED programs in airports18 and casinos19,20 and with police officers14,2123 have demonstrated a 49% to 74% survival rate from out-of-hospital witnessed VF SCA when immediate bystander CPR is provided and defibrillation occurs within 3 to 5 minutes of collapse. These high survival rates, however, are attained only in programs that reduce time to defibrillation.24
| The PAD Trial |
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Methods
Participating sites were urban and suburban communities served by EMS systems that provide advanced life support. Each site identified distinct units within their service area (eg, buildings, public areas). These units were randomly allocated to train and equip volunteers to provide either CPR only or CPR plus AED response. All of the volunteer rescuers received rigorous, standard training to recognize SCA, phone 9-1-1, and perform CPR according to AHA recommendations. Volunteers at the sites offering CPR plus AED response also were trained and equipped to use AEDs. At CPR-plus-AED sites, AEDs were placed to enable volunteers to retrieve and deliver an AED to a victim of SCA within 3 minutes of collapse.
The trial was conducted from July 2000 through September 2003. Approximately 20 000 volunteers received training in programs that offered frequent retraining and refresher drills. More than 1600 AEDs were placed to conduct the trial. Most (84%) of the study facilities were in public locations such as recreational facilities and shopping centers. Additional details of the study design and methodology have been published.25
Results
In the units providing only bystander CPR, 15 of 107 persons experiencing definite cardiac arrest (ie, an arrest of cardiac origin with rhythm identification) survived to hospital discharge. In the units providing bystander CPR plus AED response, 30 of 128 victims of definite cardiac arrest survived to discharge. This increase in the number of survivors of definite cardiac arrest in units with CPR plus AED response compared with the number of survivors in the units providing CPR response alone was statistically significant (P<0.05).26
In this study, nearly two thirds of all victims of SCA in both groups received bystander CPR. Compared with sites with CPR-only response, sites with CPR plus AED response had a shorter interval from collapse to first rhythm assessment (6 versus 8.7 minutes) and a higher incidence of VF (57% versus 47%). These differences were statistically significant. No inappropriate shocks were delivered. Adverse events were rare and consisted chiefly of stolen AEDs and transient psychological stress among rescuers.
It is important to note that residential sites represented
16% of the study sites and accounted for 28% of the cardiac arrests but <5% of the survivors. The study lacked statistical power to detect whether lay rescuer AED programs increase survival from SCA in residential settings.
| Implications for Public Policy |
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EMS databases may enable the identification of sites of cardiac arrests to better pinpoint priority sites for lay rescuer AED programs. Although the organization of information in state EMS databases varies widely, recent attempts to collect national EMS data have been encouraging.
The PAD trial5 confirms the value of the elements of the chain of survival in improving the outcome of SCA. The trial supports current AHA recommendations for lay rescuer AED programs and the emphasis on planning, training, practice of CPR, and use of AEDs. Early recognition, early CPR, and early defibrillation all contribute to an increased chance of survival from out-of-hospital SCA. The authors note that if the increased number of survivors from the PAD trial is extrapolated to all episodes of out-of-hospital SCA that occur in public locations annually in the United States, then
2000 to 4000 additional lives can be saved every year with widespread implementation of lay rescuer community AED programs. This would require the placement of AEDs in those public locations with a high incidence or likelihood of SCA (see the Figure).27
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In the PAD trial, survival with structured lay rescuer programs that included bystander CPR response was higher than previously reported by traditional EMS systems.5 This implies that public sites that do not provide AED programs may still improve survival from SCA by training volunteers to recognize cardiac arrest, phone 9-1-1, and give bystander CPR before the arrival of EMS providers.
Lay rescuer AED programs will be most cost effective if they are present at sites where at least 1 witnessed SCA is likely to occur every few years. In the PAD trial, sites were enrolled if there were at least 250 adults >50 years old present at the site during waking hours (
16 hours per day). Other criteria (eg, presence of high-risk persons) that can be used to select AED program sites are posted on the AED website (http://www.americanheart.org/ecc/PAD).
It is important to note that the PAD trial was not designed to evaluate home defibrillation or defibrillation provided by untrained rescuers. A national study is under way to evaluate home defibrillation, and the results of this study are expected to provide additional information about the potential benefits of home AED programs.
The AHA recommends critical elements for lay rescuer AED programs: healthcare provider oversight and planning, training of anticipated rescuers in CPR and use of the AED, link with the EMS system, and a plan for maintenance and quality improvement monitoring.4 The AHA has particularly emphasized the importance of training rescuers and the development and practice of a structured response plan. Even in the PAD trial, with rescuers trained to respond to SCA, resuscitation was attempted for only half of the witnessed SCA victims, and the on-site AED was used for only about one third of SCA victims. These findings suggest that rescuers may need more training or practice than that offered in the study and document that the mere presence of an AED does not ensure that it will be used when SCA occurs.
The selection of sites for potential lay rescuer AED programs and the placement of the AEDs within the site are important in the planning for the program. Published data about the most likely sites of SCA in the community27 can be used to identify potential sites for these lay rescuer AED programs (see the Figure). The AHA recommends that the AEDs be placed in the site so that they can be reached within a 1- to 1.5-minute brisk walk from any location.
| Implications for Future AHA Activities |
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All states have passed legislation or regulations that allow lay rescuer AED programs, but the heterogeneity of the state laws has created confusion for lay rescuers and has complicated attempts to establish lay rescuer AED programs. An AHA scientific statement is being developed that will delineate critical state legislative components and implementation strategies for lay rescuer AED programs.
The PAD trial results are being carefully reviewed by AHA resuscitation experts to refine recommendations for resuscitation and lay rescuer AED programs. In addition, the researchers gained experience in obtaining community informed consent and institutional review board approval.28 For further information about lay rescuer AED programs, see http://www.americanheart.org/ecc/PAD.
| Acknowledgments |
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| Footnotes |
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This statement was approved by the American Heart Association Science Advisory and Coordinating Committee on April 11, 2005. A single reprint is available by calling 800-242-8721 (US only) or writing the American Heart Association, Public Information, 7272 Greenville Ave, Dallas, TX 75231-4596. Ask for reprint No. 71-0325. To purchase additional reprints: up to 999 copies, call 800-611-6083 (US only) or fax 413-665-2671; 1000 or more copies, call 410-528-4121, fax 410-528-4264, or e-mail kgray@lww.com. To make photocopies for personal or educational use, call the Copyright Clearance Center, 978-750-8400.
Expert peer review of AHA Scientific Statements is conducted at the AHA National Center. For more on AHA statements and guidelines development, visit http://www.americanheart.org/presenter.jhtml?identifier=3023366.
| References |
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