Predictors of resuscitation outcome in a swine model of VF cardiac arrest: A comparison of VF duration, presence of acute myocardial infarction and VF waveform

Introduction: Factors that affect resuscitation to a perfusing rhythm (ROSC) following ventricular fibrillation (VF) include untreated VF duration, acute myocardial infarction (AMI), and possibly factors reflected in the VF waveform. We hypothesized that resuscitation of VF to ROSC within 3 min is predicted by the VF waveform, independent of untreated VF duration or presence of acute MI. Methods: AMI was induced by the occlusion of the left anterior descending coronary artery. VF was induced in normal (N = 30) and AMI swine (N = 30). Animals were resuscitated after untreated VF of brief (2 min) or prolonged (8 min) duration. VF waveform was analyzed before the first shock to compute the amplitude-spectral area (AMSA) and slope. Results: Unadjusted predictors of ROSC within 3 min included untreated VF duration (8 min vs 2 min; OR 0.11, 95%CI 0.02-0.54), AMI (AMI vs normal; OR 0.11, 95%CI 0.02-0.54), AMSA (highest to lowest tertile; OR 15.5, 95%CI 1.7-140), and slope (highest to lowest tertile; OR 12.7, 95%CI 1.4-114). On multivariate regression, untreated VF duration (P = 0.011) and AMI (P = 0.003) predicted ROSC within 3 min. Among secondary outcome variables, favorable neurological status at 24 h was only predicted by VF duration (OR 0.22, 95% CI 0.05-0.92). Conclusions: In this swine model of VF, untreated VF duration and AMI were independent predictors of ROSC following VF cardiac arrest. AMSA and slope predicted ROSC when VF duration or the presence of AMI were unknown. Importantly, the initial treatment of choice for short duration VF is defibrillation regardless of VF waveform.