Transthoracic defibrillation threshold of sine and trapezoidal waveforms in defibrillation.
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 greater than 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 less than 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 trapezoid and three sine waves (p greater than 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.
Regional Medical Cardiology Centre, Royal Victoria Hospital, Belfast, Northern Ireland.
C M
CM
Wilson
A
A
Bailey
J D
JD
Allen
J
J
Anderson
A A
AA
Adgey
D000818:Animals; D002304:Cardiac Pacing, Artificial; D004285:Dogs; D004554:Electric Countershock; D004562:Electrocardiography; D005260:Female; D008297:Male; D014693:Ventricular Fibrillation / Q000209:etiology / Q000628:therapy*