Abstract 101: Ventricular Fibrillation Frequency Characteristics are Altered in Acute Myocardial Infarction
Background: For brief duration ventricular fibrillation (VF), optimal therapy is prompt defibrillation. For prolonged VF, survival is improved by providing chest compressions prior to the first defibrillatory shock. Future automated external defibrillators (AEDs) are being designed to direct rescue efforts by inferring the duration of VF based on its waveform characteristics such as frequency content. This approach assumes that the VF waveform is an appropriate surrogate for VF duration and is not affected by structural heart disease. We hypothesized that an acute myocardial infarction (MI) may alter the frequency content of ventricular fibrillation (VF).
Methods: VF was induced in 11 swine with an acute MI after occlusion of the mid-left anterior descending coronary artery and in 16 control swine. VF waveforms were analyzed for mean, median, and dominant frequency, as well as bandwidth, defined as the frequency interval containing 50% of the total power about the median.
Results: All frequency characteristics were significantly (p<0.001) altered in acute MI swine compared to controls. Specifically, these characteristics were significantly depressed and varied little over time in acute MI compared to controls.
Conclusion: VF during an acute MI has altered frequency content and time evolution compared to VF without coronary obstruction. Frequency characteristics such as mean, median, dominant and bandwidth show little variation in time after an acute MI and are not suitable surrogates for VF duration. These findings have important implications for the development of “smart” AEDs designed to determine duration of VF from the waveform characteristics.