Study objective: The efficacy of a shock waveform for external defibrillati
on depends on the waveform characteristics. Recently, design principles bas
ed on cardiac electrophysiology have been developed to determine optimal wa
veform characteristics. The objective of this clinical trial was to evaluat
e the efficacy of principles-based monophasic and biphasic waveforms for ex
ternal defibrillation.
Methods: A prospective, randomized, blinded, multicenter study of 118 patie
nts undergoing electrophysiologic testing or receiving an implantable defib
rillator was conducted. Ventricular fibrillation was induced, and defibrill
ation was attempted in each patient with a biphasic and a monophasic wavefo
rm. Patients were randomly placed into 2 groups: group 1 received shocks of
escalating energy, and group 2 received only high-energy shocks.
Results: The biphasic waveform achieved a first-shock success rate of 100%
in group 1 (95% confidence interval [CI] 95.1% to 100%) and group 2 (95% CI
94.6% to 100%), with average delivered energies of 201+/-17 J and 295+/-28
J, respectively. The monophasic waveform demonstrated a 96.7% (95% CI 89.1
% to 100%) first-shock success rate and average delivered energy of 215+/-1
2 J for group 1 and a 98.2% 195% CI 91.7% to 100%) first-shock success rate
and average delivered energy of 352+/-13 J for group 2.
Conclusion: Using principles of electrophysiology, it is possible to design
both biphasic and monophasic waveforms for external defibrillation that ac
hieve a high first-shock efficacy.