Abstract P149: The Effects Of Waveform Duration On Efficacy Of A Dual Time Constant Biphasic Truncated Exponential Defibrillation Waveform
Objectives. The effects of the first and the second phase durations of a biphasic truncated exponential (BTE) waveform on defibrillation success were evaluated in a guinea pig model of ventricular fibrillation (VF). We hypothesized that the waveform duration, and especially the first phase duration, plays the main role for defibrillation efficacy in comparison to energy, current and voltage, when a dual time constant BTE shock is employed.
Materials and methods. VF was electrically induced and untreated for 5 seconds in 30 male guinea pigs weighing 1000±200g. Animals were randomized to receive one of the 5 defibrillation waveforms selected for this study, which had different durations of phase 1 and 2. A total of 125 cardiac arrest events and defibrillations were investigated for each animal.
Results. A defibrillation waveform with a first phase intermediate duration of 5 ms, yielded a higher success of defibrillation compared to the waveform with a first phase of shorter or longer duration (p<0.05). The defibrillation waveform with a first phase of intermediate duration also presented significantly lower energy, peak and average current together with lower voltage in comparison to waveforms with shorter or longer first phase durations (p<0.001). Although a longer second phase duration showed a trend toward worse defibrillation success, the differences in the duration of the second phase did not significantly affect defibrillation outcome.
Conclusions. For dual time constant BTE waveforms, an intermediate first phase duration, yielded the best defibrillation efficacy with less energy, current, and voltage compared to shorter or longer durations.