40 ZOLL AED PLUS Administrator’s Guide
Clinical Trial Results for the M Series Biphasic Waveform
The efficacy of ZOLL’s Rectilinear Biphasic Waveform has been clinically verified during a study of
defibrillation of Ventricular Fibrillation (VF)/Ventricular Tachycardia (VT). A feasibility study was
performed initially for defibrillation of VF/VT (n=20) on two separate groups of patients to ensure
waveform safety and energy selection. Subsequently a separate, multi-center, randomized clinical trial
was performed to verify the waveform’s efficacy. A description of this study is provided below. The
study was performed using ZOLL defibrillation systems consisting of ZOLL defibrillators, the ZOLL
Rectilinear Biphasic Waveform and ZOLL Multi-Function Pads.
Randomized Multi-Center Clinical Trial for Defibrillation of Ventricular Fibrillation
(VF) and Ventricular Tachycardia (VT)
Overview: The defibrillation efficacy of ZOLL’s Rectilinear Biphasic Waveform was compared to a
monophasic damped sine waveform in a prospective, randomized, multi-center study of patients
undergoing ventricular defibrillation for VF/VT during electro-physiological studies, ICD implants and
test. A total of 194 patients were enrolled in the study. 10 patients who did not satisfy all protocol criteria
were excluded from the analysis.
Objectives: The primary goal of this study was to compare the first shock efficacy of the 120J
Rectilinear Biphasic Waveform with a 200J monophasic waveform. The secondary goal was to compare
all shock (three consecutive 120, 150, 170J) efficacy of the Rectilinear Biphasic Waveform with that of
a monophasic waveform (three consecutive 200, 300, 360J). A significance level of p=0.05 or less was
considered statistically significant using Fischer’s Exact test. Also, differences between the two
waveforms were considered statistically significant when the customary 95% or AHA recommended
90%* confidence interval between the two waveforms was greater than 0%.
Results: The study population of 184 patients had a mean age of 63
±14 years. 143 patients were males.
There were no adverse events or injuries related to the study.
The first shock, first induction efficacy of biphasic shocks at 120J was 99% versus 93% for monophasic
shocks at 200J (p=0.0517, 95% confidence interval of the difference of -2.7% to 16.5% and 90%
confidence interval of the difference of -1.01% to 15.3%).
Successful defibrillation with rectilinear biphasic shocks was achieved with 58% less delivered current
than with monophasic shocks (14
±1 vs. 33 ±7 A, p=0.0001).
The difference in efficacy between the rectilinear biphasic and the monophasic shocks was greater in
patients with high transthoracic impedance (greater than 90 ohms). The first shock, first induction
efficacy of biphasic shocks was 100% versus 63% for monophasic shocks for patients with high
impedance (p=0.02, 95% confidence interval of the difference of -0.021% to 0.759% and 90%
confidence interval of the difference of 0.037% to 0.706%).
A single patient required a second biphasic shock at 150J to achieve 100% efficacy versus six patients
for whom monophasic shocks of up to 360J were required for 100% total defibrillation efficacy.
Conclusion: The data demonstrate the equivalent efficacy of low energy rectilinear biphasic shocks
compared to standard high energy monophasic shocks for transthoracic defibrillation for all patients at
the 95% confidence level. The data also demonstrate the superior efficacy of low energy rectilinear
biphasic shocks compared to standard high energy monophasic shocks in patients with high
transthoracic impedance at the 90% confidence level. There were no unsafe outcomes or adverse events
due to the use of the rectilinear biphasic waveform.
* Kerber, R., et. al., AHA Scientific Statement, Circulation, 1997; 95: 1677-1682:
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