Transthoracic defibrillation with chopping-modulated biphasic waveforms.

The superiority of different biphasic pulses for transthoracic defibrillation was proven by several studies. These efficient waveforms were implemented in some commercially available defibrillators. Recently we have devised and evaluated a biphasic waveform with a specially balanced ratio of the first-to-second phase voltages and with 5 kHz frequency 1:1 on-off chopping. It used less than half the energy for successful defibrillation in comparison with the 'classic' monophasic damped sinusoidal wave and showed considerably less post-shock negative effects. This experience led us to try several laws of chopping modulation. A pulse-width modulation, combining low energy with gradual upslope of the modelled transmembrane potential, proved to have better performance than the standard damped sinusoid wave and the non-chopped biphasic truncated exponential pulse. This waveform was tested in a series of animal experiments in comparison with other modulated pulses, with the non-modulated waveform and the standard damped sinusoid wave. The experiments demonstrated the superiority of the modulated waveform, assessed by combining the parameters of threshold defibrillation energy and of post-shock disturbances reduction.