Quantifying cardiac tissue heterogeneity using high-density grid catheter: validation in porcine model

Abstract Background and Objectives Characterizing cardiac substrate is crucial for diagnosing and treating cardiac arrhythmias due to its association with the presence of fibrotic tissue. Omnipolar Electrogram (EGM) technology provides orientation-independent signal generation and instantaneous propagation direction determination. Although traditionally, the amplitude of the bipolar signal has been the most used metric, it alone does not suffice for comprehensive tissue characterization. Recently, a novel metric has been developed to quantify the degree of directional propagation disorganization within cardiac tissue, defined as Vector Field Heterogenity (VFH)[1] that can provide additional insights to the tissue characterization. Due to the presence of tissues with varying impedance, changes in the direction of propagation of cardiac electrical signals can occur. Therefore, the objective of this study is to characterize how the presence of fibrotic or necrotic tissue can influence the disorganization of electrical activity propagation, and thus assess the effectiveness of the heterogeneity metric in characterizing these tissues. Method We worked with a database of a female swine records of the left atrium. These records include data pre and post-ablation by electroporation. From the unipolar signals available in the database, we have calculated the Omnipolar EGMs in cross configuration. From the omnipolar signals, we calculated the propagation direction. On this propagation direction, we applied the heterogeneity metric for each catheter position along all the left atrium. This metric has a normalized range between 0 and 1, 0 describing the minimum disorganization and 1 the maximum. These calculations have been applied in the same way in the registers pre and post-ablation to evaluate the differences. Results Pre-procedure bipolar peak-to-peak voltages averaged 2.7591mV (SD = 3.4257), decreasing post-procedure to 0.754mV (SD = 1.1666), (p< 0.0001) indicating a significant decrease in bipolar amplitude following ablation. Heterogeneity scores increased post-ablation (mean = 0.3753, SD = 0.21218; post: mean = 0.53526, SD = 0.1320, p<0.0001. This indicates that after ablation, not only does the signal amplitude decrease, but also the level of disorganization of electrical propagation increases. These findings are visually depicted in Figure 1. Conclusion The ablation procedure led to reduced tissue electrical activity, manifested by decreased amplitude and increased propagation heterogeneity, indicative of tissue disorganization. Transitioning from homogeneous to heterogeneous conduction post-ablation suggests the presence of necrotic tissue, hindering uniform wave propagation. This highlights the significance of heterogeneity scoring in evaluating tissue health and ablative intervention outcomes.Figure 1.Catheter HD Grid