• G Karlsson, Y Zhang, L R Davies, W Coddington, and R E Kerber.
• Department of Internal Medicine, The Cardiovascular Center, University of Iowa Hospitals and Clinics, 200 Hawkins Drive, Iowa City, IA 52242, USA.
• Resuscitation. 2001 Oct 1;51(1):77-81.

BackgroundElectrode polarity may alter the success of biphasic shocks from implantable systems. Whether the electrode polarity influences the success of transthoracic biphasic defibrillation is unknown. We determined the effect of electrode polarity on biphasic transthoracic defibrillation in a porcine model.MethodIn ten anesthetized adult pigs, 16-28 kg, electrode pads were placed in two different orientations on the chest wall; apex-right parasternal and sternal-vertebral column. Ventricular fibrillation (VF) was electrically induced and allowed to persist for 30 s. Truncated exponential biphasic shocks (5/3 ms) were delivered at 20, 30, 50, 70 and 100 J. Four shocks at each energy level were delivered to construct energy vs. % success curves for VF termination. Electrode polarity for the first pulse was varied so that the first pulse cathode was either the apex (for apex-parasternal) or sternum (for sternum-vertebral column), or the reverse. The second pulse polarity was always the opposite of the first.ResultsVF termination success rose from 0 to 86% as energy increased from 20 to 100 J. Varying the electrode polarity did not alter success rates at any energy level with either electrode pad placement.ConclusionIn this porcine model of transthoracic defibrillation, varying the biphasic shock electrode polarity did not alter transthoracic defibrillation success. Positional labeling of transthoracic biphasic defibrillation electrode pads may be unnecessary.

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