Equivalence of the standard monophasic waveform shocks delivered by automated external defibrillators?

Objective: To study whether two different types of monophasic waveform shocks (i.e. monophasic damped sinusoidal [MDS] and monophasic truncated exponential [MTE] waveform shocks) are of equivalent efficacy. Methods: Retrospective review of defibrillation efficacy and outcome in ventricular fibrillation/ventricular tachycardia (VF/VT) patients treated in the same EMS system with AEDs delivering either MDS waveform shocks (n = 40) or MTE waveform shocks (n = 40). Results: Defibrillation efficacy of the first shock was 82.5% in the MDS group and 70% in the MTE group (P = 0.19). Termination of VF by at least one of the first three shocks was found in 95 and 85% of the patients treated with MDS and MTE waveform shocks, respectively (P = 0.22). Restoration of spontaneous circulation occurred in 75% of the MDS group and 30% of the MTE group (P = 0.0001). Hospital admission rates were 52.5% in the MDS group and 17.5% in the MTE group P = 0.001). Hospital discharge rates were 17.5% in the MDS group and 7.5% in the MTE group (P = 0.18). Conclusions: Our data suggest disparity in efficacy between MDS waveform shocks and MTE waveform shocks. Furthermore, our findings should be taken into consideration when the issue of the control group(s) in future clinical trials on new waveforms is discussed. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.