Abstract 19492: Successful Reversed Polarity Defibrillation With the Wearable Cardioverter Defibrillator

Abstract

Introduction: Published literature suggests that switching the direction of the external defibrillation pathway does not impact the efficacy of the shock. Consequently, the European Resuscitation Council Guidelines for Resuscitation 2010 states that it does not matter, for defibrillation success, which electrode is placed in either position. The primary objective of this study was to evaluate if these results are consistent for the asymmetrical electrodes of a wearable defibrillator, which uses two large posterior and one apical self-gelling defibrillator electrodes. Methods: Six swine were fibrillated and defibrillated at each energy level (75J, 100J, 125J, or 150J) during apex-posterior defibrillation comparing an initially positive apex electrode (standard) with an initially negative apex electrode (reversed) using a customized wearable cardioverter defibrillator (WCD, LifeVest®, ZOLL). The first three swine received the standard shocks first, while the last three swine received the reversed shocks first. If the first shock did not convert the rhythm, rescue shocks were delivered by either the WCD at 150J or an external defibrillator at 200J until conversion took place. Shock success and ECGs were recorded for all shocks. Fisher’s exact test was used to determine P-values. Results: Six swine were studied (average wt = 28.3 ± 3.0 kg, range: 24.0-31.8 kg). All energy levels (75J, 100J, 125J, and 150J) were tested at least once using both normal and reversed electrodes on all pigs. The first-shock results (excluding the rescue shocks) are shown in the figure below. No animal died from irreversible VF, asystole, or pulseless electrical activity during the study. No differences in defibrillation success were found to be significant at any energy level. Conclusions: In this animal model of VF, the polarity of the apex-posterior shocks did not influence transthoracic defibrillation success by the asymmetric electrodes of the WCD.