Automatic external defibrillators: lessons from the past, present and future

Semiautomated external defibrillators for in-hospital early defibrillation: a comparative study

OBJECTIVES

Semiautomated external defibrillators (AEDs) should be considered as a means to facilitate in-hospital early defibrillation (IHED) in areas where advanced life support rescuers are not readily available. In this study, we aimed to develop a checklist and a measurement protocol to evaluate and compare AEDs by assessing factors that may affect IHED.

METHODS

A clinical and technical comparison of six AEDs was performed. Technical specifications were analyzed, while an emergency team evaluated ergonomics and appropriateness for IHED at Bambino Gesù Children's Hospital. A measurement protocol was implemented, which aimed to assess the ability of defibrillators to recognize shockable and nonshockable rhythms, accuracy of delivered energy, and charging time.

RESULTS

Designs of AEDs differed in several features which influence their appropriateness for IHED. Some units showed poor ergonomics and instructions/feedback for cardiopulmonary resuscitation. Differences between defibrillators in recognizing shockable and nonshockable rhythms emerged for polymorphic ventricular tachycardia waveforms and when the frequency and amplitude of input signals varied. Tests for accuracy revealed poor performances at low and high impedance levels for most AEDs. Notably, differences greater than 20 seconds were found in the time from power-on to "ready for discharge."

CONCLUSIONS

The approach we used to assess AEDs allowed us to evaluate their appropriateness with respect to the organizational context, to measure their parameters, and to compare models. Results showed that ergonomics and/or performances (timing and accuracy) could be improved in each device.

Mechanisms of ventricular fibrillation initiation in MADIT II patients with implantable cardioverter defibrillators

BACKGROUND

The availability of stored intracardiac electrograms from implantable defibrillators (ICDs) has facilitated the study of the mechanisms of ventricular tachyarrhythmia onset. This study aimed to determine the patterns of initiation of ventricular fibrillation (VF) in Multicenter Automatic Defibrillator Implantation Trial (MADIT) II patients along with associated electrocardiogram (ECG) parameters and clinical characteristics.

METHODS

Examination of stored electrograms enabled us to evaluate the rhythm preceding each episode of VF and to calculate (intracardiac) ECG parameters including QT, QT peak (QTp), coupling interval, and prematurity index.

RESULTS

Sixty episodes of VF among 29 patients (mean age 64.4 +/- 2.5 years) were identified. A single ventricular premature complex (VPC) initiated 46 (77%) episodes whereas a short-long-short (SLS) sequence accounted for 14 (23%) episodes. Of the 29 patients studied, 23 patients had VF episodes preceded by a VPC only, two patients with SLS only, and four patients with both VPC and SLS-initiated episodes. There were no significant differences between initiation patterns in regards to the measured ECG parameters; a faster heart rate with SLS initiation (mean RR prior to VF of 655 +/- 104 ms for SLS and 744 +/- 222 ms for VPC) approached significance (P = 0.06). The two patients with SLS only were not on beta-blockers compared to 83% of the VPC patients.

CONCLUSION

Ventricular fibrillation is more commonly initiated by a VPC than by a SLS sequence among the MADIT II population. Current pacing modes designed to prevent bradycardia and pause-dependent arrhythmias are unlikely to decrease the incidence of VPC-initiated episodes of VF.

A public access defibrillation programme in non-inpatient hospital areas

INTRODUCTION

Automatic external defibrillators (AED) have proven to be valuable and life saving for out of hospital cardiac arrests. Their use in hospital arrests is less well documented, but they offer the opportunity to improve survival in the hospital setting also.

METHODS

The implementation of a public access defibrillation (PAD) programme at a tertiary care hospital is described, with reference specifically to targeting areas where time from arrest to arrival of defibrillation would be greater than 3 min.

RESULTS

Nine AEDs were placed in areas of the hospital distant from inpatient or outpatient floors. The locations of the AEDs were chosen based on a 3 min walk from currently available defibrillators to all areas of the hospital, including parking garages and walkways from building to building. In this programme AED use in non-inpatient hospital locations resulted in the resuscitation of a patient in ventricular fibrillation.

CONCLUSION

PAD in non-inpatient hospital settings can be life saving and similar programmes should be considered for other hospitals.

Reconfirmation algorithms should be the standard of care in automated external defibrillators

Non-sustained and self-terminating arrhythmias pose a significant challenge during resuscitation. Delivery of a defibrillation shock to a non-shockable rhythm has a poorly understood effect on the heart. The importance of assessing rhythm right up until the delivery of a shock is of increased importance when "blind" shocks are being delivered by automatic defibrillators or minimally trained rescuers. Reconfirmation algorithms are common in current-generation implantable defibrillators but this investigation of current-generation AEDs shows that only 71% of devices presently available have reconfirmation algorithms. A case of spontaneous reversion of a non-sustained arrhythmia is presented. The implications of delivering a defibrillator shock to a non-shockable rhythm are discussed.

In hospital cardiac arrest: a role for automatic defibrillation

INTRODUCTION

Sudden cardiac death (SCD) survival decreases by 10% for each minute of delay in defibrillation, however, survival rates of 98% can be achieved when defibrillation is accomplished within 30s of collapse. Recently, a fully automated external cardioverter-defibrillator (AECD) was approved by the FDA for in-hospital use. The AECD can be programmed to automatically defibrillate when a life threatening ventricular arrhythmia occurs. The purpose of this study was to assess the potential impact of in-hospital AECDs on the critical time to defibrillation in monitored hospital units.

METHODS

Mock emergency (n = 18) were conducted using simulated ventricular fibrillation in various monitored units. Observers were stationed to record the time staff responded to the arrhythmia, and the time to shock. These times were compared to an AECD protocol that defibrillates automatically in an average of 38.3 s from onset of arrhythmia (n = 18).

RESULTS

Staff versus AECD response time to arrhythmia (s) was 76.3 +/- 113.7 (CI 19.8-132.8) versus 7.6 +/- 0.6 (CI 7.3-7.9). Staff versus AECD time to shock was 169.2 +/- 103.1 (CI 117.9-220.4) versus 38.3 +/- 0.7 (CI 37.9-38.6). P-values are <0.0001 for differences between the groups.

CONCLUSION

The use of AECDs on monitored units would significantly reduce the critical time to defibrillation in patients with SCA. We anticipate this would translate to improved survival rates, and better neurologic outcomes.

The benefits and use of shock advisory defibrillators in hospitals

Survival to discharge following a cardiac arrest is dependent on rapid and effective basic and advanced life support. Paramount to a rapid response is access to sufficiently trained health care providers, who have a duty to perform basic life support and initiate early defibrillation. In hospitals, defibrillation remains the domain of specially prepared staff and the type of defibrillator used might be crucial to rapid and effective defibrillation. The advent of automatic external defibrillators has increased the range of people who can use a defibrillator successfully. For nurses, arguably a lack of familiarity about the benefits of and the use of automatic external defibrillators are the greatest barriers to nurse-initiated defibrillation programmes. This paper explores the use of automatic external defibrillators, their relationship to the associated defibrillator waveforms and the benefits of their use by registered nurses within the hospital setting.

AED use in businesses, public facilities and homes by minimally trained first responders

BACKGROUND

Automated external defibrillators (AEDs) have become increasingly available outside of the Emergency Medical Systems (EMS) community to treat sudden cardiac arrest (SCA). We sought to study the use of AEDs in the home, businesses and other public settings by minimally trained first responders. The frequency of AED use, type of training offered to first responders, and outcomes of AED use were investigated. In addition, minimally trained responders were asked if they had encountered any safety problems associated with the AED.

METHODS

We conducted a telephone survey of businesses and public facilities (2683) and homes (145) owning at least one AED for at least 12 months. Use was defined as an AED taken to a medical emergency thought to be a SCA, regardless of whether the AED was applied to the patient or identified a shockable rhythm.

RESULTS

Of owners that participated in the survey, 13% (209/1581) of businesses and 5% (4/73) of homes had responded with the AED to a suspected cardiac arrest. Ninety-five percent of the businesses/public facilities offered training that specifically covered AED use. The rate of use for the AEDs was highest in residential buildings, public places, malls and recreational facilities with an overall usage rate of 11.6% per year. In-depth interviews were conducted with lay responders who had used the AED in a suspected cardiac arrest. In the four cases where the AED was used solely by a lay responder, all four patients survived to hospital admission and two were known to be discharged from the hospital. There were no reports of injury or harm.

CONCLUSIONS

This survey demonstrates that AEDs purchased by businesses and homes were frequently taken to suspected cardiac arrests. Lay responders were able to successfully use the AEDs in emergency situations. Further, there were no reports of harm or injury to the operators, bystanders or patients from lay responder use of the AEDs.

Technologic advances and program initiatives in public access defibrillation using automated external defibrillators

Widespread provision of early defibrillation following cardiac arrest holds major promise for improved survival from ventricular fibrillation. The critical element in predicting a successful outcome is the rapidity with which defibrillation is achieved. A worldwide awareness of this potential and its advocacy by such organizations as the American Heart Association have been pivotal in the evolution of initiatives to make defibrillation more widely and more rapidly available. The feasibility of this initiative, known as public access defibrillation, is in large measure a direct consequence of major technologic advances in automated external defibrillators (AEDs). New low-energy waveforms with biphasic morphology have been shown to be more effective in terminating ventricular fibrillation and may do so with less myocardial injury. Placement of AEDs in a variety of nontraditional settings such as police cars, aircraft and airport terminals, and gambling casinos has been shown to yield an impressive number of survivors of cardiac arrest in ventricular fibrillation. Questions yet to be answered center on the appropriate disposition of AEDs in public access defibrillation settings, training and retraining issues, device maintenance, and collection of accurate data to document benefit and to identify areas of needed improvement or expansion of AED availability.

Barriers and facilitators to the prescription of automated external defibrillators for home use in patients with heart disease: a survey of cardiologists

OBJECTIVE

Because the majority of cardiac arrests occur at home, the use of automated external defibrillators (AEDs) in the home could potentially improve survival of out-of-hospital cardiac arrest. Currently, physicians must prescribe AEDs for home use by patients. The purpose of this study was to investigate the barriers and facilitators to prescription of home use of AEDs.

DESIGN

Telephone interviews were conducted with 85 cardiologists and paper and pencil surveys (via fax) with 59 additional cardiologists in Washington State.

OUTCOME MEASURES

Cardiologists were asked about their current practices and their perceived barriers and facilitators to prescription of AEDs for home use.

RESULTS

Eighty-five percent of the sample believed that AEDs could be effective in preventing death, although only 7% of the cardiologists had ever prescribed an AED. Reasons for nonprescription included the use of implantable cardioverter defibrillators, perceived lack of a clear patient niche, and lack of knowledge about the device. The majority of respondents reported that they would be more likely to prescribe AEDs if they were the standard of care (71%), were covered by insurance (67%), and came with comprehensive training (58%).

CONCLUSION

The results showed that cardiologists believe that home use of AEDs can be effective but that many issues regarding the prescription of AEDs remain.

Automatic external defibrillators: changing the way we manage ventricular fibrillation

OBJECTIVE

To discuss recent developments in automatic defibrillation and to review the evidence that first-responders equipped with automatic external defibrillators (AEDs) improve survival from out-of-hospital cardiac arrest.

DATA SOURCES

MEDLINE search from 1966 to 1999 (articles in English only) and examination of bibliographies.

STUDY SELECTION

Published studies of out-of-hospital cardiac arrest and first-responders equipped with AEDs. Studies had to have a control group and to report survival to hospital discharge from ventricular fibrillation (VF).

DATA EXTRACTION

Six studies met the selection criteria (two prospective randomised trials, two prospective controlled trials, and one cohort study and one retrospective study, both with historical controls).

DATA SYNTHESIS

A random effects meta-analysis of odds ratios for survival from VF.

CONCLUSIONS

Meta-analysis suggests that equipping first-responders with AEDs increases the probability of survival to hospital discharge after out-of-hospital cardiac arrest (odds ratio, 1.74; 95% CI, 1.27-2.38; P < 0.001). However, most of the studies lacked sufficient power to draw definitive conclusions. Until the impact of wide deployment of AEDs is fully understood, first-responder defibrillation in Australia should only occur as part of coordinated multicentre research studies.