Waveforms for defibrillation and cardioversion: recent experimental and clinical studies

PURPOSE OF REVIEW: The advent of biphasic waveforms for external defibrillation has generated extensive experimental and clinical investigation. At the same time, it has led to the development and clinical use of biphasic waveforms of several different designs. Finally, other types of waveforms, primarily triphasic, have entered experimental evaluation. RECENT FINDINGS: There is virtually universal agreement that biphasic waveforms, regardless of design, have greater efficacy in defibrillation of ventricular fibrillation and in cardioversion of atrial fibrillation when compared with monophasic waveforms. It remains unresolved, however, whether any specific biphasic waveform has greater clinical superiority than others. Likewise, it remains to be demonstrated whether any biphasic waveform is less injurious to myocardial function than another and whether injury, if it is incurred, is secondary to peak delivered current or to delivered energy. Biphasic truncated exponential waveforms are used by most manufacturers, whereas a rectilinear biphasic waveform and a pulsed waveform also are being used clinically. SUMMARY: Biphasic waveforms have supplanted monophasic waveforms for defibrillation and cardioversion. They include biphasic truncated exponential, rectilinear, and pulsed biphasic versions. At this time, there is no certain evidence of clinical superiority of one waveform over another in terms of either efficacy or myocardial injury.