Abstract 2081: Ischemia Produces a Reduction of Frequency Characteristics in Early Ventricular Fibrillation
Introduction: Most animal studies of VF waveform characteristics are of healthy animals with VF initiated by electric shock. Clinical VF is often the result of ischemia. Waveform characteristics in these two types of VF may differ. The angular velocity (AV), frequency ratio (FR) and median frequency (MF) are three frequency based measures of VF. The scaling exponent and the logarithm of the absolute correlations are two measures of the fractal dimension of VF.
Hypothesis: We hypothesized that these quantitative measures would differ between ischemic and electrically initiated VF.
Methods: VF was induced in 14 swine by electric shock and in 18 swine by ischemia. For ischemic VF animals, an angioplasty catheter was positioned in the mid-LAD and the balloon inflated. A mean of 891 +/− 608 (SD) sec later, VF occurred. For electrical animals, VF was induced by passing AC current through a catheter in the RV. VF was recorded for 7 minutes. Sequential 5 second epochs were analyzed for AV, FR, MF and fractal dimension measures using MATLAB.
Results: The electrical and ischemic VF groups did not differ significantly with regard to measures of fractal dimension (scaling exponent and logarithm of the absolute correlations). During the initial 90 seconds the groups did differ in all measures of frequency as follows (see FR, fig. 1⇓) : AV (p<0.001), FR (p<0.001), MF (p<0.001).
Conclusion: Ischemic VF in swine produces no change in the fractal dimension but does result in a significant decrease in frequency during the initial 90 seconds when compared to electrically induced VF. This early decrease in frequency may have important clinical implications regarding the likelihood of success of therapies.