Introduction: Monophasic defibrillation waveforms are presently the standard of care in clinical use for trans-thoracic defibrillation. Recently, there has been renewed interest in biphasic waveforms. This interest reflects the superior performance demonstrated with biphasic waveforms in implantable defibrillators (ICD). External defibrillation research on two biphasic truncated exponential waveforms has been reported in which the waveforms were compared clinically to a damped sine waveform. A limitation of these transthoracic waveforms is the insufficiency of fundamental design principles used to determine the waveform characteristics.

Methods: We developed design principles to determine the optimal waveform characteristics of an external biphasic truncated exponential waveform based on myocardial cell response model. The cell response model incorporates critical transthoracic elements into a recently published and experimentally validated intracardiac model used to design ICD waveforms. We determined the optimal leading-edge voltage (LEV), phase durations (in milliseconds, Ph1 D, Ph2 D), and delivered energies (ED) for the reported external biphasic waveforms (WF) using the model with 78 W for trans-chest resistance. We compared our results against those reported for the biphasic waveforms.