Can an RC membrane model predict the efficacy of a defibrillation waveform: an analysis of defibrillation mechanisms in 140 defibrillation waveforms

Abstract

Different defibrillation waveforms exhibit different efficacies. It has been proposed that a resistor-capacitor (RC) model of the myocardial membrane can explain these differences. Both the maximum capacitor voltage (charge banking) and the remaining voltage after the pulse (charge burping) have been proposed as efficacy predictors. In this paper, we test these hypotheses against 140 defibrillation waveforms. Data is reported from 159 guinea pigs. For each tested waveform, we calculated to within a fixed constant the minimum and maximum voltage on the capacitor, and the voltage remaining after the shock for time constants (/spl tau/) between 0.1 ms and 4.0 ms. Each parameter was tested to determine if it would be predicted to have a 10% impact on defibrillation efficacy. No parameter was a significant predictor of defibrillation efficacy for /spl tau/>2.0 ms. The maximum voltage was significant for short time constants (/spl tau/<=2.0 ms, p<0.005). For the very short time constants (<=0.5 ms) the voltage remaining was significant (p<0.05), and, for the shortest time constants (t=0.1 ms), the minimum voltage was a significant predictor (p<0.05).