New concepts in transthoracic defibrillation

First described in humans in 1956, transthoracic defibrillation has been the focus of experimental and clinical studies since its inception. Monophasic waveforms dominated defibrillation until 1996, when the first biphasic waveform became available for clinical use. Much interest has centered on defining the mechanisms of defibrillation and on elucidating the mechanisms that account for the superior efficacy of biphasic waveforms. This article discusses the proposed mechanisms of defibrillation, the theoretical basis for greater efficacy of biphasic waveforms, clinically available biphasic waveforms and their circuitry, and the clinical data describing experience with these waveforms.