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

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. Here, we test these hypotheses against 140 defibrillation waveforms. METHODS Data is reported from 159 guinea pigs. 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 (τ) 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. RESULTS No parameter was a significant predictor of defibrillation efficacy for τ>2.0ms. The maximum voltage was significant for short time constants (τ<=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).

Duke Scholars

Author Robert A. Malkin Biomedical Engineering