Original article
Transthoracic defibrillation threshold of sine and trapezoidal waveforms in defibrillation

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Abstract

The transthoracic defibrillation threshold of trapezoidal (2.5-, 5-, 10-, 15-, 20-, 40-, and 55-msec duration) and damped sine waveforms were established in groups of anesthetized greyhounds. Of the seven trapezoidal waveforms, the threshold current was lowest for the 20-msec pulse but was not significantly different for the 5–20-msec pulses (p > 0.05). The threshold delivered energy was not significantly different for the 2.5–20-msec waveforms. The 40- and 55-msec pulses had significantly greater delivered energies than the shorter pulses (p < 0.01). The transthoracic defibrillation threshold of two trapezoidal (5- and 20-msec) and three damped sine waves (Lown, Edmark, and Belfast) showed that the threshold transthoracic current and energy were not significantly different for the 5-msec teapezoid and three sine waves (p > 0.05). The threshold transthoracic energy for the 20-msec trapezoid was significantly greater than that of the four other waveforms. The threshold current for the 20-msec trapezoid was significantly less than that of the Belfast and Edmark waveforms only. Thus, none of the three damped sine waveforms was superior, with the 5-msec trapezoid producing similar results. Although the 20-msec trapezoid had the lowest threshold current, it had the highest delivery energy.

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    Dr. Wilson is a recipient of a Royal Victoria Hospital, Belfast, Research Fellowship.

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