A prospective randomized evaluation of biphasic versus monophasic waveform pulses on defibrillation efficacy in humans

Abstract

Biphasic waveforms have been suggested as a superior waveform for ventricular defibrillation. To test this premise, a prospective randomized intraoperative evaluation of defibrillation efficacy of monophasic and biphasic waveform pulses was performed in 22 survivors of out of hospital ventricular fibrillation who were undergoing cardiac surgery for implantation of an automatic defibrillator. The initial waveform used in a patient for defibrillation testing, either monophasic or biphasic, was randomly selected. Subsequently, each patient served as his or her own control for defibrillation testing of the other waveform. The defibrillation threshold was defined as the lowest pulse amplitude that would effectively terminate ventricular fibrillation with a single discharge delivered 10 s after initiation of an episode of ventricular fibrillation induced with alternating current. Each defibrillation pulse was recorded oscilloscopically, and defibrillation pulse voltage, current, resistance and stored energy were measured. Fifteen (68%) of the 22 patients had a lower defibrillation threshold with the biphasic pulse, 3 (14%) had a lower threshold with the monophasic pulse and 4 (18%) had equal defibrillation thresholds (within 1.0 J) regardless of waveform. The mean leading edge defibrillation threshold voltage was 317 +/- 105 V when the monophasic pulse was used and 267 +/- 102 V (16% less) when the biphasic pulse was used (p = 0.008). Mean leading edge defibrillation threshold current was 7.9 +/- 3.7 A when the monophasic pulse was used and 6.8 +/- 3.8 A (14% less) when the biphasic pulse was used (p = 0.051).(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of Phase Duration of Biphasic Waveforms on Defibrillation Energy Requirements With a 70-μF Capacitance

“…Internal defibrillation energy requirements can be reduced by using biphasic instead of monophasic waveforms, 8 by use of an active can configuration 9 or by choosing the optimal electrode polarity. 10,11 The current study focuses on the influence of different phase durations on defibrillation energy requirements with a 70-F capacitance.…”

Comparison of Outcomes After Use of Biphasic or Monophasic Defibrillators Among Out-of-Hospital Cardiac Arrest Patients

“…Furthermore, the equipment is smaller and lighter. [10][11][12] Sellers of defibrillators seem to consider that biphasic defibrillators are equal to or better than the monophasic defibrillator in improving outcomes of OHCA patients. Purchasers are also assumed to expect improved outcomes of OHCA patients with the biphasic defibrillator, and this may be a factor in replacing the monophasic defibrillator with the biphasic defibrillator.…”

Defibrillation Shock Amplitude, Location and Timing

“…Although this method may not offer the same accuracy as the dose-response curve or the limited defibrillation threshold testing (Figure 2.3B), it was reliable, predictive and the long-term survival of these patients was not affected (Rosenheck et al, 2009b). After implementation of the biphasic shock (Bardy et al, 1989) and the unipolar defibrillation system (Bardy et al et al, 1993) in the implantable defibrillators, the defibrillation threshold decreased much below the device capacity and testing with single defibrillation attempt is justified (Higgins et al, 2005). Moreover, as previously mentioned, the need of testing was seriously questioned (Viskin & Rosso, 2009).…”