Multicenter study of principles-based waveforms for external defibrillation

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.