Comparison of a novel rectilinear biphasic waveform with a damped sine wave monophasic waveform for transthoracic ventricular defibrillation

OBJECTIVES We compared the efficacy of a novel rectilinear biphasic wavefor m, consisting of a constant current first phase, with a damped sine wave mo nophasic waveform during transthoracic defibrillation. BACKGROUND Multiple studies have shown that for endocardial defibrillation, biphasic waveforms have a greater efficacy than monophasic waveforms. More recently, a 130-J truncated exponential biphasic waveform was shown to hav e equivalent efficacy to a 200-J damped sine wave monophasic waveform for t ransthoracic Ventricular defibrillation. However, the optimal type of bipha sic waveform is unknown. METHODS In this prospective, randomized, multicenter trial, 184 patients wh o underwent Ventricular defibrillation were randomized to receive a 200-J d amped sine wave monophasic or 120-J rectilinear biphasic shock. RESULTS First-shock efficacy of the biphasic waveform was significantly gre ater than that of the monophasic waveform (99% vs. 93%, p = 0.05) and was a chieved with nearly 60% less delivered current (14 +/- 1 vs. 33 +/- 7 A, p < 0.0001). Although the efficacy of the biphasic and monophasic waveforms w as comparable in patients with an impedance <70 Omega (100% [biphasic] a. 9 5% [monophasic], p = NS), the biphasic waveform was significantly more effe ctive in patients with an impedance greater than or equal to 70 Omega (99% [biphasic] vs. 86% [monophasic], p = 0.02). CONCLUSIONS This study demonstrates a superior efficacy of rectilinear biph asic shocks as compared with monophasic shocks for transthoracic ventricula r defibrillation, particularly in patients with a high transthoracic impeda nce. More important, biphasic shocks defibrillated with nearly 60% less cur rent. The combination of increased efficacy and decreased current requireme nts suggests that biphasic shocks as compared with monophasic shocks are ad vantageous for transthoracic ventricular defibrillation. (C) 1999 by the Am erican College of Cardiology.