Accuracy of the Automatic External Defibrillator in Children
Abstract & Commentary
Synopsis: One commercially available AED analysis algorithm exhibited excellent sensitivity and specificity in the pediatric age group for ventricular fibrillation and nonshockable rhythms.
Source: Cecchin F, et al. Circulation. 2001;103:2483-2488.
Cecchin and colleagues studied the accuracy of an arrhythmia detection algorithm used in a commercially available automatic external defibrillator (AED) in pediatric arrhythmias. At the present time, AED use is not recommended for children younger than 8 years of age because of a paucity of data about AED function in this population. Cecchin et al prospectively collected arrhythmias from 4 centers in patients who were thought to be at high risk because they were undergoing electrophysiologic study, were ill in the intensive care unit, or were undergoing cardiac surgery. For these children, a commercially available AED was modified to function as a 30-minute loop recorder with a wide band ECG recording system. Defibrillation capability was disabled and only the detection algorithm was tested. Appropriately sized and positioned defibrillation pads were used to record the rhythms. In addition, 82 rhythm strips obtained from 57 children were acquired from other centers. These tracings were converted into a digital format and also tested using the AED algorithm. Rhythms were classified into 3 groups: 1) shockable rhythms (ventricular fibrillation, polymorphic ventricular tachycardia [VT], or VT with a rate more than 250 bpm); 2) intermediate rhythms (slower VT); and 3) nonshockable rhythms including supraventricular arrhythmias, ventricular ectopic beats, idioventricular rhythms, and asystole.
The recordings were classified by a panel of 3 pediatric electrophysiologists who assumed that the patient is unresponsive, is of unknown age, who may or may not have a pulse, and who the AED cannot deliver a synchronized shock.
The AED algorithm used characterizes the electrocardiogram in terms of 4 characteristics: rate, morphologic stability, rapidly conducted electric signals, and signal amplitude.
The study included prospectively or retrospectively collected data from 191 children who provided a total of 669 rhythm strips for analysis. There were 74 patients younger than 1 year of age and 62 patients between 1 and 8 years of age. The remaining 55 patients ranged in age from 8 to 12. Heart disease was present in 73% of the children. The rhythm strips analyzed were classified as nonshockable in 463 cases, shockable in 131 cases, and intermediate in 102 cases. The AED algorithm demonstrated a sensitivity of 96% for ventricular fibrillation and 71% for rapid ventricular tachycardia. The algorithm had a specificity of 100% for sinus rhythm, supraventricular arrhythmias, ventricular premature beats, idioventricular rhythms, and asystole. These values met or exceeded American Heart Association goals for AED performance for all rhythms except for rapid VT.
Cecchin et al concluded that 1 commercially available AED analysis algorithm exhibited excellent sensitivity and specificity in the pediatric age group for ventricular fibrillation and nonshockable rhythms. They suggest the use of 1 algorithm for both adults and children is feasible and should be effective.
Comment by John P. DiMarco, MD, PhD
The principles and techniques of resuscitation require some modifications when applied to infants and children. In adults, cardiac arrest is often sudden, and a ventricular tachyarrhythmia in the setting of acute or chronic ischemic heart disease is the most frequent etiology. Even among hospitalized or critically ill adult patients, cardiac arrest is frequently caused by an episode of unanticipated VT or ventricular fibrillation. Cardiac arrest in children is an uncommon event. In the out-of-hospital setting, it is most often the result of submersion/near drowning, trauma, poisoning, choking, or respiratory failure. In the hospital, it is often the terminal event of progressive shock, respiratory failure, sepsis, or metabolic disorders. Ventricular fibrillation and ventricular tachycardia are the rhythms at the time of arrest in only between 10% and 25% of patients. Because of these differences between children and adults in cardiac arrest epidemiology, only limited data about pediatric resuscitation are available.
The introduction of AED technology has greatly simplified training in and delivery of advanced cardiac life support for adults. However, the lack of data about AED use in pediatric populations means that different equipment is theoretically now required to provide ACLS for both groups.
The data in this paper suggest that currently available diagnostic algorithms in at least 1 commercially available AED are accurate enough to cover all age groups. Arrhythmia detection is, however, not the only function of an AED. In children, shock energy is often based on weight and the standard adult setting would not be appropriate. If the AED used in a child has an operator-selectable energy setting, it should function adequately during the resuscitation of an infant or child. This is available in the AED units commonly found in hospitals or used by emergency medical systems. Perhaps a caution about energy selection in children could be added to the instruction screens of AED models used in these settings. The AED models that are designed for use by minimally trained personnel usually deliver only shock energies that are appropriate for adults, and modifying them for optimal use in infants and young children would increase their complexity.
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