Nonlinear organization of electrocardiogram and optical signals during ventricular fibrillation

Background: Although sympathetic activation may induce ventricular fibrillation (VF), little is known about how the autonomic nervous system influences its nonlinear organization. This study tested the hypothesis that autonomic receptor activation altered the nonlinear organization of VF. Methods: Isolated rabbit hearts underwent retrograde perfusion with acetylcholine or norepinephrine added to the perfusate. Voltage-sensitive fluorescent images of the ventricular surface were obtained during sustained VF. Concurrent electrocardiogram and optical pixel signals underwent recurrence quantification analysis, which detects and quantifies patterns of repeating data sequences. Recurrence quantification analysis variables signify different aspects of nonlinearity. Results: Recurrence quantification analysis results showed that the electrocardiogram and pixel signals did not exhibit the same pattern of nonlinear organization during VF. Recurrence quantification analysis values were not dramatically altered from baseline by acetylcholine and norepinephrine but instead exhibited considerable variation. Conclusion: An alteration in autonomic milieu diminished the nonlinear organization of VF, that is, autonomic receptor activation made VF less likely to behave in a repetitive pattern over time.