Biphasic versus sequential pulse defibrillation: a direct comparison in humans

It has been demonstrated recently that both biphasic and sequential pulse defibrillation shocks are superior to monophasic defibrillation shocks in animals and humans. There is little information directly comparing these two waveforms when pulse characteristics, subjects, and total electrode surface areas are kept constant. We determined the defibrillation threshold intraoperatively in 12 patients undergoing arrhythmia surgery, with the use of two or three patch electrodes (Medtronic 6891 and 6892), while keeping the electrode surface area constant. Patients were randomized in a crossover design for determinations of defibrillation threshold by means of biphasic and sequential pulse shocks. Leading-edge delivered current and delivered energy were significantly lower with sequential pulse shocks than with biphasic shocks (delivered energy means +/- SEM 3.6 +/- 0.7 joules vs 5.5 +/- 0.9 joules, respectively). We conclude that sequential pulse defibrillation with three defibrillating electrodes provides an important current delivery system not matched by biphasic shocks with two electrodes when subjects, waveform characteristics, and total electrode surface areas are kept constant.