Do triangular and trapezoidal waveforms affect the effectiveness of transthoracic ventricular defibrillation in anesthetized dogs?
In a canine model, defibrillation success depends on waveform shape and energy, demonstrating that long low-amplitude tails and excessive energy are detrimental to reversing ventricular fibrillation.
From 7, 200 fibrillation-defibrillation episodes in anesthetized dogs, the effectiveness of 6 classes of unidirectional shocks in reversing ventricular fibrillation of 30-sec duration was determined. The shocks lasted for 1 to 256 msec. Three waveforms (ascending ramp triangular, descending ramp triangular, and trapezoidal) were studied at peak currents of 10 amp and 20 amp. Families of curves of per cent success vs. energy were derived from the data for the 6 classes of waveforms studied and from corresponding curves for 3 classes of unidirectional square-wave shocks previously studied by our group. The families of curves were used as a basis for an analysis of the influence of various parameters on the effectiveness of shocks. We conclude that an appropriate energy content is a necessary, but not sufficient condition for effective ventricular defibrillation, that long, low-amplitude tails on shocks are detrimental and that excessive energy content is detrimental.
Schuder et al. (Sat,) studied this question.