Efficacy of monophasic electrical impulses with steep leading and trailing edges in cardiac defibrillation

Experiments on dogs were performed to investigate the efficacy of various defibrillation impulse waveforms. The results showed that the decisive factors for the effectiveness of the defibrillation impulse of certain shape are its relationship to the carciac tissue accomodation and the duration of the suprathreshold current flow. For cardiac defibrillation the most convenient impulse is therefore the impulse with the highest rate of rise of the leading edge as well as the trailing edge. The amplitude of the rear trailing edge of the defibrillation impulse should be either equal or higher than the amplitude of the front leading edge. That means that rectangular or trapezoidal impulses with an ascending slope may be most conveniently used for cardiac defibrillation. The biologically optimal duration of the trapezoidal impulse with an ascending slope proved to range from 7 to 14 msec. The authors emphasize the inevitability of additional characteristics of the defibrillation impulse by its peak current and total energy contents.