• Karen M Darragh, Ganesh Manoharan, Cesar Navarro, Simon J Walsh, John D Allen, John McC Anderson, and Aa Jennifer Adgey.
• Belfast Health and Social Care Trust, Belfast, UK.
• Eur Heart J Acute Cardiovasc Care. 2012 Dec 1; 1 (4): 285-90.

ObjectiveOptimization of defibrillation success is important to improve efficacy and minimize post-shock sequelae. Previous work has suggested an improvement in shock success when an intracardiac shock is delivered synchronized to the upslope of a VF wave. We investigated the efficacy of transthoracic defibrillation success using a novel external biphasic defibrillator which delivers shocks synchronized to the upslope of the surface ECG.MethodsA prospective, controlled, randomized study in a research institute laboratory of male and female pigs (54.2±1.8 kg). Ventricular fibrillation (VF) was induced in 10 anaesthetized and ventilated pigs. Shocks were delivered randomly from a biphasic defibrillator in synchronized or non-synchronized mode via self-adhesive electrode pads following 30 s of VF. Energy settings at 50, 70, 80, and 100J were randomly tested. VF amplitude, impedance, and shock outcome were recorded and analysed digitally.ResultsA total of 300 shocks were delivered. Synchronized shocks were delivered on the upslope of the VF wave in 99% of cases. There was no significant difference in shock success between shocks delivered in synchronized or non-synchronized modes (p=0.695). There was no significant difference in the amplitude of VF between successful and unsuccessful shocks (p=0.163). Furthermore, there was no association between shock success and transthoracic impedance.ConclusionThe novel defibrillator used in this study was able to consistently deliver shocks on the upslope portion of the VF wave but did not show an improvement in shock success.

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