Abstract 12820: Predictors of Resuscitation in a Swine Model of Vf Cardiac Arrest: Amplitude Spectral Area (amsa) and Slope Predict a Return of Spontaneous Circulation Independent of the Presence of a Prior Non-Acute Myocardial Infarction
Introduction: We have previously demonstrated in a swine model of cardiac arrest due to ventricular fibrillation(VF) that a return of spontaneous circulation (ROSC) following a defibrillation shock is predicted by the VF waveform (amplitude spectral area, AMSA, and slope) in normal and acutely ischemic (acute MI) states. The utility of the VF waveform to predict defibrillation is unknown in the healed myocardial infarction (post-MI) state. We hypothesized that the VF waveform predicts ROSC following a defibrillatory shock independent of the presence of a prior MI.
Methods: MI was induced in swine by placement of a plug in the mid left anterior descending artery. Post-MI animals recovered for two weeks, and VF was induced. Normal swine without prior infarction were used as controls. VF was left untreated for 8 minutes and then resuscitation was commenced with a defibrillation shock followed by two minutes of chest compressions (CC), epinephrine, and ventilation. Cycles of shocks and CC were repeated until ROSC was obtained, defined as a systolic aortic pressure greater than 50 mm Hg and pulse pressure > 20mm Hg lasting at least one minute. VF waveform characteristics (AMSA and slope) were calculated from the VF waveform immediately preceding each shock. Predictors of ROSC following a shock were evaluated by logistic regression with random effects with AMSA and slope analyzed by tertiles.
Results: 10 normal and 10 post-MI swine were studied, with a total of 43 shocks. Post-MI animals required more shocks than normal animals to achieve ROSC (2.5 ± 2.1 vs 1.8 ± 1.5, P<0.01). The attainment of ROSC following a shock was predicted by both AMSA (OR = 10 for AMSA between 17–37 mV-Hz, P=0.05, and OR=85 for AMSA>37 mV/Hz , P=0.001) and slope (OR=11 for slope between 1.7 to 3.3 mV/sec, P=0.05 and OR=210 for slope >3.3 mV/sec, P<0.001), but the achievement of ROSC following a shock was not dependent upon the myocardial state (normal vs post-MI).
Conclusions: VF waveform characteristics are highly predictive of achieving ROSC following a defibrillatory shock, independent of the presence of a prior myocardial infarction. This implies that algorithms to direct timing of defibrillation of shocks based on waveform may not need to take into account the underlying myocardial state.
- © 2010 by American Heart Association, Inc.