Abstract 2626: Intramyocardial High-Energy Phosphate Depletion during Ventricular Fibrillation Correlates with Electrocardiographic Change
Background: Ventricular fibrillation (VF) is highly energy-wasteful, producing no perfusion. High-energy phosphates (HEPs) deplete rapidly during VF, adding to metabolic/ischemic stress and adversely affecting VF. We have shown that the scaling exponent (ScE) of the VF waveform predicts rescue shock outcome and can be used to guide decision-making during CPR.
Hypotheses: We hypothesized that intramyocardial HEPs would rapidly diminish during untreated VF, and that this decrease would correlate with changes in the ScE.
Methods: We anesthetized and instrumented 18 domestic swine (26.6 ± 1.9 kgs). We systematically assigned them (6 per group) to 5, 10, or 15 minutes of untreated VF, which was induced with a transthoracic shock. At the predetermined timepoint open-chest biopsies were taken from the left ventricle. Biopsied tissue samples were immediately flash frozen in a slurry of dry ice and isopentane (-90o C), and HEPs were extracted with 1% trichloroacetic acid. Levels of ATP and ADP were measured luminometrically with an ADP/ATP ratio kit. ATP and ADP levels were assayed in duplicate, and the average recorded (reported in nmol/mg myocardial tissue). Fifteen seconds of ECG signal was digitally recorded (for ScE analysis) immediately prior to biopsy. ScE values were paired with ATP and ADP for calculation of linear regression. HEPs vs. time were compared with ANOVA.
Results: Mean ATP/ADP were 1.20/0.21 at 5 min, 0.94/0.12 at 10 min, and 0.45/0.11 at 15 min. ATP correlated with ScE (r=.63, p=0.009) but ADP did not (r=.35, p=0.17). Both ATP (p=0.004) and ADP (p=0.024) differed over time.
Conclusions: HEPs rapidly diminish during untreated VF. ATP depletion correlates with ScE change.