Comparison of biphasic and monophasic defibrillation waveforms in an isolated rabbit heart preparation.

STUDY OBJECTIVE

The aims were to develop a Langendorff rabbit heart model and to compare monophasic and biphasic defibrillation pulses.

DESIGN

Hearts were perfused with a Krebs-Henseleit solution and two 1.4 cm2 Pt-Ir mesh patch electrodes were sutured onto the ventricles. A 5 ms monophasic or 10 ms biphasic pulse, with randomly selected voltages of 30, 50, 70, 90, 110, or 130 V, defibrillated the heart after 10 s of fibrillation.

SUBJECTS

11 adult male New Zealand white rabbits weighing 2.8(0.27) kg, were used for the studies.

MEASUREMENTS AND MAIN RESULTS

A total of 72 fibrillation and defibrillation sequences were conducted in each preparation. The results were fitted to a sigmoidal dose-response curve by logistic regression analysis. Voltage and energy values from the fitted data at 50% and 80% success (V50, V80, E50, E80) indicated a significantly lower (p less than 0.05) defibrillation threshold voltage and energy for the biphasic waveform [V50 = 48 (SD19) V, V80 = 87(27) V, E50 = 0.15(0.12) J, E80 = 0.48(0.29) J] compared with the monophasic waveform [V50 = 79(20) V, V80 = 110(20) V, E50 = 0.27(0.12) J, E80 = 0.5(0.12) J]. There was no observed difference in defibrillation success rate between the first and second halves of any study.

CONCLUSIONS

The Langendorff rabbit heart model is suitable for assessing electrical fibrillation and defibrillation mechanisms. Defibrillation can be achieved with a lower energy when using a biphasic rather than a monophasic pulse.