Strength-Duration Curves for Ventricular Defibrillation in Dogs

Abstract

The threshold voltage and current necessary for ventricular defibrillation was measured in dogs using capacitor-discharge and half-sinusoidal pulses of current of various durations. From these quantities the electrical strength required for defibrillation was determined and expressed as energy, peak current, and charge per gram of heart. The optimum current duration depends on the criterion selected. It was found that with half-sinusoidal current, less energy, current, and charge were required; this type of waveform approximates that delivered by capacitor-inductor defibrillators. For minimum energy with this waveform, the optimum duration range is 1.25 to 8.3 msec and the energy required is approximately 7 mw-sec per gram of heart. For minimum current, the optimum duration is 8.3 msec; with this duration the peak half-sinusoidal current is about 30 mamp per gram of heart. There is no clearly defined duration for minimum charge for capacitor-discharge or half-sinusoidal current.

Electrical Dose for Ventricular Defibrillation of Large and Small Animals Using Precordial Electrodes

“…Various inductance and capacitance combinations were used to obtain a wider range of pulse duration (0.3-30 ms) than is employed in human defibrillation in order that the full clinical range could be evaluated. Data from a previous study (9) Table I presents the threshold-delivered energies and peak currents used to defibrillate all of the animals studied. The values for threshold energy and body weight for the entire duration range (0.3-30 ins) are plotted in Fig.…”

“…3 These data also show that it is possible to achieve defibrillation with pulse durations longer and shorter than those presently in clinical medicine (3-10 ms). However before quantification of these.two dose concepts and comparing the animal data to man, it is necessary to recognize that the duration of the pulse of defibrillating current importantly affects the threshold energy and peak current required for defibrillation (9). To elucidate this point and.…”

Efficacy and safety of the reciprocal pulse defibrillator current waveform

“…No statistically significant differences (p = 0.05) in current threshold were found between the 10 ms waveforms (single pulse, dual 5 ms pulses and the reciprocal 5 ms pulses). The 5 ms single-pulse current threshold was significantly higher (p = 0.05) than the current thresholds of the other three waveforms of longer total duration, as would be expected from the strength/duration concept for defibrillation (GEDDES et al, 1970). Fig.…”

“…Also, the safety factors of these three 10 ms waveforms are not significantly different (p = 0.05) than the 5 ms single pulse. The higher defibrillation threshold current density for the 5 ms single pulse is expected because of the well known strength/duration relationship for tissue stimulation and defibrillation (GEDDES et al, 1970;KONING et al, 1975;BOURLAND et al, 1978a). Hence, if the total pulse duration is held constant, there is no physiological advantage to the reciprocal pulse waveform.…”

Current is better than energy as predictor of success for biphasic defibrillatory shocks in a porcine model of ventricular fibrillation

“…This was consistent with Geddes's report, in which the energy threshold increased as a result of prolonged shock duration, while peak current requirement for defibrillation was minimal for an optimal shock duration of 8.3 ms when strength-duration curve was investigated. 35 From the result obtained in this study we may extrapolate that increases in energy, as a result of increased current while keeping defibrillation duration optimal, would maintain the strength-duration curve and would be beneficial for shock success. In contrast, increases in energy, as a result of lengthening the waveform duration when pathway impedance increases, would move down the strength-duration curve and increase the energy requirement for successful defibrillation, as observed in Fig.…”