Quantitative assessment of synchronization during atrial fibrillation by shannon entropy characterization of propagation delays

This study introduced a new method for the quantflcation of rhe synchronization (S) and the causal verse of activation (S12) in couples of atrial electrograms recorded during atrial fibrillation (AF). The synchronizarion indexes S and SI2 relied on the measure of the propagation delays between coupled activation times in two atrial signals and on the characterization of thkir dispersion by Shannon-Entropy (SE). S and SI2 were validated both on simulated activation time series and endocavitary signals in patients. In simulation, S and SI2 were equal to 1 for propagation of one single wavefront in a fully excitable tissue, while they decreased for reenfries in partially excitable tissue (S = 0.70 ± 0.05, SI2 = 0.66 ± 0.05 ) and multiple wavelet propagation (S = 0.46 ± 0.06, SI2 = 0.39 ± 0.08). In patients S, was equal to 1 during atrial flutter (AFI) and decreased with increasing complexity of AF (AF1: S = 0.76 f 0.05; AFZ: S = 0.56 ± 0.06; AF3: S = 0.39 ± 0.08). Moreover SI2 evidenced the preservation of a correct activation sequence during AFL and AFI (SI2 = S) and its loss during AF2 (SI2 = 0.41 ± 0.12 -= S) and AF3 (SI2 = 0.26 ± 0.03 < S). As indirect markers of the electrophysiological properties of atrial tissue, indexes S and SI2 may provide a new insight in understunding the mechanisms initiating and maintaining AF and support new clinical treatments for its interruption.