Abstract 210: A Comparison of Short Duration Ventricular Fibrillation and Long Duration Ventricular Fibrillation Defibrillation Thresholds
Introduction: Much work has been performed to investigate defibrillation threshold (DFT) in Short Duration Ventricular Fibrillation (SDVF). Even though SDVF and Long Duration Ventricular Fibrillation (LDVF) are now known to be maintained by different mechanisms, little research has been performed to evaluate how DFT varies with VF duration.
Methods: External defibrillation with biphasic, truncated exponential shocks was performed in 6 domestic swine. A ramp-up shock protocol was performed in which the first shock was 100 J and shocks were given increasing in magnitude by 0.1 log energy steps until VF was halted. First the SDVF DFT was determined with the first shock given 20 s after VF induction. Five min after the last SDVF DFT was determined, LDVF was induced. After 5 min of LDVF, chest compressions and ventilation were initiated. Three min later the first shock was given, 2 energy steps below the SDVF DFT. After a successful shock, VF was immediately reinitiated. For every 1 min of elapsed time shocks were delivered until a DFT was determined.
Results: The SDVF mean±SD DFT was 160±48 J, and the LDVF mean DFT was 161±73 J (p=NS by paired t-test). The LDVF DFTs were normalized with respect to the SDVF DFTs for each animal (see figure). Linear regression was performed on the normalized DFT values with respect to time which indicated that no significant difference in the slope of the regression line and a slope of zero (p = NS) Conclusions The DFT during SDVF and LDVF was not significantly different, and the LDVF DFT did not change with multiple DFT determinations. Therefore, this methodology of determining DFTS during LDVF and chest compressions in swine provides a stable platform for evaluating and optimizing shock waveforms. This finding is important because even though SDVF and LDVF are known to be maintained by different mechanisms, little research has been performed to evaluate how the DFT varies with different shock waveforms in LDVF.
- © 2010 by American Heart Association, Inc.