Characterization of Atrial Propagation Patterns and Fibrotic Substrate With a Modified Omnipolar Electrogram Strategy in Multi-Electrode Arrays

Abstract

Introduction: The omnipolar electrogram method was recently proposed to try to generate orientation-independent electrograms. It estimates the electric field from the bipolar electrograms of a clique, under the assumption of locally plane and homogeneous propagation. The local electric field evolution over time describes a loop trajectory from which omnipolar signals in the propagation direction, substrate and propagation features, are derived. In this work, we propose substrate and conduction velocity mapping modalities based on a modified version of the omnipolar electrogram method, which aims to reduce orientation-dependent residual components in the standard approach.Methods: A simulated electrical propagation in 2D, with a tissue including a circular patch of diffuse fibrosis, was used for validation. Unipolar electrograms were calculated in a multi-electrode array, also deriving bipolar electrograms along the two main directions of the grid. Simulated bipolar electrograms were also contaminated with real noise, to assess the robustness of the mapping strategies against noise. The performance of the maps in identifying fibrosis and in reproducing unipolar reference voltage maps was evaluated. Bipolar voltage maps were also considered for performance comparison.Results: Results show that the modified omnipolar mapping strategies are more accurate and robust against noise than bipolar and standard omnipolar maps in fibrosis detection (accuracies higher than 85 vs. 80% and 70%, respectively). They present better correlation with unipolar reference voltage maps than bipolar and original omnipolar maps (Pearson's correlations higher than 0.75 vs. 0.60 and 0.70, respectively).Conclusion: The modified omnipolar method improves fibrosis detection, characterization of substrate and propagation, also reducing the residual sensitivity to directionality over the standard approach and improving robustness against noise. Nevertheless, studies with real electrograms will elucidate its impact in catheter ablation interventions.

Atrial conduction velocity mapping: clinical tools, algorithms and approaches for understanding the arrhythmogenic substrate

“…Since the CV from omnipolar analysis is obtained from a ratio of signals, it does not necessitate specific activation times [7]. In [56], the technique is modified to estimate the omnipolar electrogram after inter-electrogram alignment within each clique to reduce the residual angular dependency of the classical omnipolar electrogram. In addition, [56] use the ratio of standard deviations = ([ φ] SD ∕[E a ] SD ) ̂ rather than peak-to-peak amplitudes, with the aim of reducing the effects of noise on the estimate.…”

Atrial fibrosis identification with unipolar electrogram eigenvalue distribution analysis in multi-electrode arrays

“…Simulated signals were corrupted with noise excerpts obtained from real u-EGMs, as previously done in [8]. Two thousand different noise segments were extracted from u-EGMs recorded with a multi-electrode PentaRay ® catheter (Biosense-Webster, Inc., Diamond Bar, CA, USA) at intervals with no recorded EGMs.…”

“…At each catheter position, u-EGMs were considered in the following five four-electrode cliques, according to the pole numbering in Fig. 4: (3,4,7,8), (7,8,11,12), (11,12,15,16), (15,16,19,20), (19,20,3,4) and the five-electrode clique (4,8,12,16,20), for their smaller inter-electrode spacing. As example, cliques (3,4,7,8) and (4,8,12,16,20) are depicted in Fig.…”

“…4: (3,4,7,8), (7,8,11,12), (11,12,15,16), (15,16,19,20), (19,20,3,4) and the five-electrode clique (4,8,12,16,20), for their smaller inter-electrode spacing. As example, cliques (3,4,7,8) and (4,8,12,16,20) are depicted in Fig. 4.…”

“…Atrial fibrosis is electrophysiologically characterized by low intracardiac electrograms (EGMs) amplitudes and conduction velocities [8], which may be measured with electroanatomical mapping (EAM) systems [9]. These allow displaying 3D voltage and activation time maps over a reconstruction of cardiac chambers anatomy and visualizing catheter position, so as to guide ablation procedures and treat arrhythmias with minimum radiation exposition [10].…”