Systematic evaluation of the determinants of defibrillation efficacy

Pediatric defibrillation shocks alone do not cause heart damage in a porcine model

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AEDs utilize specific low energy pediatric modes to reduce myocardial damage.

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This study applied various shocks in sinus rhythm without cardiac instrumentation.

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Isolated clinically relevant shock sequences do not result in myocardial damage.

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Typical variations in pediatric shocks did not affect safety and efficacy.

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These results may inform future pediatric resuscitation guidelines.

Aim

Automated external defibrillators (AEDs) use various shock protocols with different characteristics when deployed in pediatric mode. The aim of this study is to assess and compare the safety and efficacy of different AED pediatric protocols using novel experimental approaches.

Methods

Two defibrillation protocols (A and B) were assessed across two studies: Protocol A: escalating (50–75–90 J) defibrillation waveform with higher voltage, shorter duration and equal phase durations. Protocol B; non-escalating (50–50–50 J) defibrillation waveform with lower voltage, longer duration and unequal phase durations.

Experiment 1: Isolated shock damage was assessed following shocks to 12 anesthetized pigs. Animals were randomized into two groups, receiving three shocks from Protocol A (50–75–90 J) or B (50–50–50 J). Cardiac function, cardiac troponin I (cTnI), creatine phosphokinase (CPK) and histopathology were analyzed. Experiment 2: Defibrillation safety and efficacy were assessed through shock success, ROSC, ST-segment deviation and contractility following 16 randomized shocks from protocol A or B delivered to 10 anesthetized pigs in VF.

Results

Experiment 1: No clinically meaningful difference in cTnI, CPK, ST-segment deviation, ejection fraction or histopathological damage was observed following defibrillation with either protocol. No difference was observed between protocols at any timepoint. Experiment 2: all defibrillation types demonstrated shock success and ROSC ≥ 97.5%. Post-ROSC contractility was similar between protocols.

Conclusions

There is no evidence that administration of clinically relevant shock sequences, without experimental confounders, result in significant myocardial damage in this model of pediatric resuscitation. Typical variations in AED pediatric mode settings do not affect defibrillation safety and efficacy.

Double (dual) sequential defibrillation for refractory ventricular fibrillation cardiac arrest: A systematic review

INTRODUCTION

Cardiac arrests associated with shockable rhythms such as ventricular fibrillation or pulseless VT (VF/pVT) are associated with improved outcomes from cardiac arrest. The more defibrillation attempts required to terminate VF/pVT, the lower the survival. Double sequential defibrillation (DSD) has been used for refractory VF/pVT cardiac arrest despite limited evidence examining this practice. We performed a systematic review to summarize the evidence related to the use of DSD during cardiac arrest.

METHODS

This review was performed according to PRISMA and registered on PROSPERO (ID: CRD42020152575). We searched Embase, Pubmed, and the Cochrane library from inception to 28 February 2020. We included adult patients with VF/pVT in any setting. We excluded case studies, case series with less than five patients, conference abstracts, simulation studies, and protocols for clinical trials. We predefined our outcomes of interest as neurological outcome, survival to hospital discharge, survival to hospital admission, return of spontaneous circulation (ROSC), and termination of VF/pVT. Risk of bias was examined using ROBINS-I or ROB-2 and certainty of studies were reported according to GRADE methodology.

RESULTS

Overall, 314 studies were identified during the initial search. One hundred and thirty studies were screened during title and abstract stage and 10 studies underwent full manuscript screening, nine included in the final analysis. Included studies were cohort studies (n = 4), case series (n = 3), case-control study (n = 1) and a prospective pilot clinical trial (n-1). All studies were considered to have serious or critical risk of bias and no meta-analysis was performed. Overall, we did not find any differences in terms of neurological outcome, survival to hospital discharge, survival to hospital admission, ROSC, or termination of VF/pVT between DSD and a standard defibrillation strategy.

CONCLUSION

The use of double sequential defibrillation was not associated with improved outcomes from out-of-hospital cardiac arrest, however the current literature has a number of limitations to interpretation. Further high-quality evidence is needed to answer this important question.

Ventricular fibrillation and defibrillation

Cardiac arrest in children is not often due to a disturbance in rhythm that is amenable to electrical defibrillation, contrary to the situation in adults. When a shockable rhythm is present, defibrillation using an external electric shock applied at an early stage after pre-oxygenation and chest compressions is of proven efficacy. Success at conversion of ventricular fibrillation is dependent on the delay before delivering the shock and defibrillation efficiency, which is itself a function of thoracic impedance, energy dose and waveform.