Electrocardiographic evaluation of defibrillation shocks delivered to out-of-hospital sudden cardiac arrest patients
Introduction
During out-of-hospital resuscitation attempts of cardiac arrest victims, the patient’s electrocardiogram (ECG) may undergo complex and dynamic transitions. Following a defibrillation attempt, such electrocardiographic instability challenges accurate assessment of defibrillation efficacy and post-shock rhythm (Fig. 1). With such a large number of transitions possible, the exact time of ECG assessment may influence the determination of defibrillation efficacy and post-shock rhythm. Presently, there is no precise definition of defibrillation efficacy in the out-of-hospital setting that is consistently used [1].
Out-of-hospital studies typically define defibrillation success as termination of VF and include post-shock organized rhythms and asystole as successful resulting rhythms [2], [3], [4], [5], [6]. Although this definition seems accurate, it lacks the crucial element of post-shock time. A defibrillation attempt may be deemed successful or unsuccessful depending on when the post-shock rhythm is assessed. If reported at all, the exact time of rhythm assessment following shock delivery is not consistent among published studies. Gliner et al. [2] and Poole et al. [3] defined defibrillation as termination of VF into an organized rhythm or asystole for 5 s post-shock, while the presence of VF at that time was considered a failed attempt. White [4] defined defibrillation as termination of VF for 3 s and distinguished transient termination from sustained termination of VF. Behr et al. [5] also defined defibrillation as termination of VF and included organized rhythms and asystole as successful resulting rhythms; however, the post-shock analysis time was not reported. Weaver et al. [6] assessed rhythms 5–15 s after shock delivery. By their definition, defibrillation successfully occurred if VF was not the first recognizable rhythm; successful rhythms included supraventricular and idioventricular rhythms and asystole. Such lack of uniformity makes it difficult to compare the effectiveness of different defibrillation therapies. A uniform definition of defibrillation efficacy and shock performance in a resuscitation protocol is therefore needed.
The primary objective of this study was to characterize out-of-hospital cardiac arrest rhythms at serial post-shock intervals with the goal of precisely defining defibrillation efficacy and establishing uniform criteria for the evaluation of shock performance. The secondary objective of this study was to compare rhythm characterizations following low-energy impedance-compensating biphasic and high-energy monophasic damped sine shocks.
Section snippets
Methods
A retrospective review was conducted of all AED uses from November 1990 to December 1998 in Rochester, MN, population 78 000. One AED use outside the city was also included, when city paramedics provided care after initial first responder defibrillation. During the study period, a combined police and paramedic emergency response program was in place. Police officers and paramedics, trained and equipped with AEDs, were simultaneously dispatched to the scene of cardiac arrests. The first
Results
Monophasic AEDs were used on 87 patients with VF as their initial monitored rhythm, while biphasic AEDs were used on 29 VF patients (Table 1). There were no significant differences in patient gender or age. There were also no significant differences in the percentage of patients having their arrest witnessed or receiving bystander CPR. The emergency call to shock interval was also not statistically different between the two groups.
As designed, the delivered energy and current were significantly
Definition of defibrillation
Given that post-shock rhythm is a function of post-shock time, what is the appropriate time to assess defibrillation efficacy? Cardiac mapping studies indicate that the defibrillation occurs within a half-second after shock delivery [7], [8]. However, this time-interval is typically not interpretable using an external defibrillator. Extending significantly beyond the actual defibrillation event may subject the assessment to confounding variables unrelated to actual shock delivery. For example,
Summary
Post-shock time and shock waveform affected post-shock rhythm. At each analysis time, there were more patients in VF following high-energy monophasic shocks than following low-energy biphasic shocks. Due to refibrillation, the percentage of patients in VF increased as post-shock time increased; the rate of VF recurrence was not a function of shock type, indicating that refibrillation is largely a function of the underlying myocardial derangement. Based on these observations, we recommend that
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Pre-Arrival Care of the Out-of-Hospital Cardiac Arrest Victim
2023, Emergency Medicine Clinics of North AmericaDoes the choice of definition for defibrillation and CPR success impact the predictability of ventricular fibrillation waveform analysis?
2017, ResuscitationCitation Excerpt :Only rhythms for which there was consensus between the doctors who were blinded to the purpose of the studies were included. To study the impact of definition of shock/CPR success on the predictive value of AMSA, we used 3 slightly modified different criteria previously described in the literature: (1) termination of VF (ToVF): no presence of VF in the 5 s analysis window13; (2) return of organized electrical activity (ROEA): an OR observed in the 5 s analysis window15,17; (3) return of a potentially perfusing rhythm (RPPR): OR is restored within 60 s after shock delivery with a heart rate greater than 40 beats/min and sustained for a period greater than 30 s.8,12 Results were presented as mean ± standard deviation (SD).
Biphasic versus monophasic defibrillation in out-of-hospital cardiac arrest: A systematic review and meta-analysis
2013, American Journal of Emergency MedicineCitation Excerpt :The 2010 AHA/ILCOR guidelines [6] define successful defibrillation as the absence of Vf five seconds after shock delivery that is not influenced by other subsequent interventions such as chest compression and ventilation. Post-shock transition into asystole or organized rhythm was considered as successful defibrillation [21]. Therefore, we extracted the results recorded five seconds after first shock delivery, which were further categorized into Vf termination (ie, post-shock transition into non-shockable rhythm, including asystole and other organized rhythms) and the return of organized rhythm (ie, post-shock transition into organized rhythms).