Synchrony Analysis of Unipolar Cardiac Mapping during Ventricular Fibrillation

Ventricular Fibrillation (VF) is one of the main causes of death in developed countries. Recent studies have shown that fibrillation have a complex organization scheme. This work uses three measures of synchrony to characterize three groups of rabbit hearts. These groups consist of rabbits trained with physical exercise (N=7), untrained rabbits treated with a drug (N=13) and a control group of untrained rabbits (N=15). Cardiac mapping records were acquired using a 240-electrode array placed on left ventricle of isolated rabbit hearts, and VF was induced pacing at increasing rates. Two acquisitions were performed: maintained perfusion, and ischemic damage produced by an artery ligation. The used measures are Spatial Correlation (SC), Coupling Index (CI) and Synchrony Index (SI), previously proposed to study fibrillation arrhythmias. These measures were used to quantify the synchrony level between a reference electrode and its neighbors at 4 increasing radiuses, increasing its electrode spacing. The significance of the effects of radius, group and its interaction was tested using the Generalized Estimating Equations methodology. The obtained results have shown that these synchrony measures provide a feasible way to characterize the three groups, where the effects of the interaction between group and radius (p<0.001), and the individual effect of the radius were statistically significant (p<0.01), both for maintained perfusion and with ischemic damage. All the groups decrease its synchrony as electrode spacing increases, as it was observed in the three used measurements. Within this perspective, the drugged group has shown the lowest synchrony reduction. The trained group have shown similarities with the control group.