Direct comparison of monophasic, biphasic and sequential pulse defibrillation over a single current pathway

Defibrillation waveform and its spatial and temporal distribution are important determinants of its efficacy. Previous comparisons of monophasic, biphasic and sequential waveforms have used one current pathway for monophasic and biphasic defibrillation and two pathways for sequential defibrillation thus confounding a direct comparison of the waveforms.

This study compared monophasic, biphasic and sequential pulse defibrillation over a single current pathway using a nonthoracotomy and a thoracotomy lead system in a dog model.

Eight mongrel dogs (mean weight 21.6+/-2.9 kg) first underwent nonthoracotomy defibrillation testing followed by a median sternotomy and implantation of two 13.9 cm2 epicardial patch electrodes posterior = cathode). Nonthoracotomy electrode configuration consisted of a right ventricular catheter (cathode) and a chest wall subcutaneous patch (anode). After 10 s of alternating current induced ventricular fibrillation, defibrillation was attempted with a test shock. Monophasic, biphasic and sequential shocks of 10 ms total duration were compared. Biphasic and sequential shocks consisted of two 5 ms components separated by 0.25 ms switch time constant. Four trials of five leading edge voltages were performed for each waveform and stepwise logistic regression analysis was used to determine 80% probability of successful defibrillation (E80). For epicardial defibrillation, E80s were monophasic 11.3+/-1.5 J; biphasic 7.9+/-1.2 J; and sequential 12.1+/-1.4 J. For nonthoracotomy defibrillation, E80s were monophasic 17.7+/-3.4 J; biphasic 13.8+/-3.3 J; and sequential 18.2+/-3.5 J. The mean E80 for biphasic pulses was significantly lower than monophasic or sequential pulses for either lead system.

Biphasic pulses are superior to monophasic or sequential pulses delivered over a single current pathway.