Nonlinear characteristics of ventricular fibrillation depend on myocardial infarction locations

The location of the myocardial infarction (MI) might induce a change in the characteristics of cardioelectric signals recorded during ventricular fibrillation (VF). In the literature, spectral analysis has been used to characterize VF, however, spectral parameters do not account for nonlinear information on these signals. The aim of this work was to analyze the effect of the location of the infarcted area on VF signals by using nonlinear parameters, hence complementing their spectral characterization. We included patients with chronic MI (28 anterior, 29 inferior) from Hospital Universitario Virgen de la Arrixaca (Murcia) and Hospital Universitario Gregorio Maranόn (Madrid) in Spain. VF was induced during cardioverter defibrillator implant. We computed the following spectral parameters: dominant frequency (f_d), organization index (oi), and regularity index (ri). We also computed the following nonlinear indices: sample entropy (SampEn), and higher order moments, kurtosis (K) and skewness (S). Statistical differences between Anterior and Inferior MI patients was assessed by a hypothesis tests based on bootstrap resampling. None of the spectral measures showed significantly differences between Anterior and Inferior groups. However, all of the nonlinear indices were significantly different. SampEn was higher in Inferior MI patients, whereas K and S were lower in Anterior MI patients. Nonlinear and higher order moments indices (SampEn, K and S) showed significant differences during VF depending on the MI localization. Therefore, nonlinear indices might help to complement spectral indices characterizing VF signals.