Immediate termination of fibrillation at 50% probability of overall success correlates with defibrillation dose-response curve width.
BACKGROUND
Issues in transthoracic defibrillation, including waveform shape, fixed versus escalating dose protocol, and low- versus high-energy shocks, can be addressed by examining the defibrillation dose-response curve. We tested the hypothesis that, for commonly used defibrillation waveforms, the steepness of the overall defibrillation dose-response curve, measured as normalized curve width, correlates with the probability of a successful defibrillation being immediate at the shock intensity producing 50% success.


RESULTS
We used 16 isolated rabbit hearts to determine probability of overall success as a function of shock intensity and probability that a successful defibrillation is immediate rather than progressive (followed by several extrasystoles) at the shock intensity producing 50% overall defibrillation success. Two waveform pairs were tested--a monophasic damped sine versus a biphasic truncated exponential waveform commonly used for transthoracic defibrillation, and a monophasic/biphasic truncated exponential waveform pair similar to those used in internal cardioverter defibrillators. There was a close correlation between probability of a successful defibrillation being immediate at 150 and normalized curve width for the defibrillation dose-response curve.


CONCLUSIONS
Our findings suggest that a high probability of successful defibrillation being immediate at low shock intensities is correlated with a narrow normalized curve width for the defibrillation dose-response curve.
Tovar
Oscar H
OH
Department of Physiology and Biophysics, Georgetown University, Washington, DC, USA.
Snyder
David E
DE
Jones
Janice L
JL
D000200:Action Potentials; D000818:Animals; D047548:Defibrillators; D004554:Electric Countershock / Q000379:methods*; D066298:In Vitro Techniques; D011336:Probability; D011817:Rabbits