Abstract 13959: Topographical Impedance Patterns Within Epicardial Ventricular Scar

Abstract

Introduction: During pericardial electroanatomical mapping of the ventricles, impedance changes within regions of epicardial scar can be observed, but their extent and relevance are not well understood. We aimed to characterize the impedance maps within the epicardial scar of patients who underwent first-time epicardial scar ablation. Methods: In this retrospective single center analysis, we identified 69 consecutive patients with structural heart disease that underwent successful first-time pericardial mapping with an irrigated contact force-sensing catheter (ThermoCool ST; Biosense Webster Inc) between 2015-2020. Among them, 37 patients were included as they had both available voltage map with epicardial scar regions and its compatible impedance map. Characteristics of impedance variations with the epicardial low voltage zone (0.5-1.5 mV) were analyzed. Abrupt impedance increases ( AIi ) were defined as impedance delta of >100Ω increase between points <1 cm apart. Results: Among 37 patients (61.4 ± 14.5 years old, male 94.6%, LVEF 38.2±14.2% and ischemic cardiomyopathy 32.4%), AIi was observed in 11 of 37 patients (29.7%). Baseline characteristics of those with AIi was similar to those without. Lateral right ventricle and apical locations demonstrated AIi more frequently compared to other sites (P<0.01). The maximum impedance was significantly higher at sites with AIi than without (425.5±58.6 vs 242.9±60.8 Ω, P<0.01) despite similar average contact force. However, impedance at sites of ablation were noted to be not significantly different between those with and without AIi, in consequence of avoiding ablation in the regions of high impedance. Conclusion: This study identified different topographical characteristics of the impedance over the ventricular epicardium. This epicardial impedance variation within low voltage regions needs to be further characterized and its clinical implications better understood.