Abstract P53: Four Electrocardiogram Waveform Measures Quantify Differences between Electrically Induced and Ischemically Induced Ventricular Fibrillation
Background: Analysis of the ECG has been shown to be useful to estimate the duration of VF in swine and the probability of successful defibrillation in animals and in patients. We use four methods to analyze the waveform: the logarithm of the absolute correlations (LAC): the median slope (MS): the angular velocity (AV): the amplitude spectrum area (AMSA). We hypothesized that VF produced by ischemia differs from electrically induced VF when analyzed by these measures.
Methods: Electrical VF (EVF) was induced in 10 anesthetized and instrumented swine using electrical stimulation of the endocardium. Ischemic VF (IVF) was induced in 10 animals by occlusion of the LAD. After 7 min of VF, chest compressions were performed for 1 min followed by defibrillation. The response to shock was recorded as ROSC if a BP of 60 mmHg was present. LAC, MS, AV and AMSA were calculated on sequential 5 second epochs of VF for 7 minutes. VF was analyzed in segments from1 to 3 minutes, 3 to 4 minutes, and 4 to 7 minutes using the generalized estimating equations method in SAS. Probability of ROSC at first shock was also evaluated for IVF and EVF groups.
Results: Differences in curves for all four measures were significant for minutes 1–3 and 4 –7. Curves are shown in Figure⇓. No measure was significant for minute 3– 4. Probability of ROSC at first shock was 50% in the electric VF group and 10% in the ischemic VF group (p=0.039 for mean LAC prior to shock).
Conclusions: EVF differs significantly from IVF for all measures both in early VF from 1–3 minutes and late VF from 4 –7 minute. All methods may be valid in predicting “down time” and choosing CPR first or Shock first.