Bipolar Electrogram Shannon Entropy at Sites of Rotational Activation: Implications for Ablation of Atrial Fibrillation
Background—The pivot is critical to rotors postulated to maintain atrial fibrillation (AF). We reasoned that wavefronts circling the pivot should broaden the amplitude distribution of bipolar electrograms, due to directional information encoded in these signals. We aimed to determine if Shannon entropy (ShEn), a measure of signal amplitude distribution, could differentiate the pivot from surrounding peripheral regions, and thereby assist clinical rotor mapping.
Methods and Results—Bipolar EGM recordings were studied in 4 systems: (i) Computer simulations of rotors in a 2D atrial sheet; (ii) Isolated rat atria recorded with a multi-electrode array (n=12); (iii) Epicardial plaque recordings of induced AF in hypertensive sheep (n=11); and (iv) Persistent AF patients (n=10). In the model systems, rotation episodes were identified, and ShEn calculated as an index of amplitude distribution. In humans, ShEn distribution was analyzed at AF termination sites and with respect to CFE-mean. We analyzed rotation episodes in simulations (4 cycles) and animals (rats: 14 rotors, duration 80±81 cycles, sheep: 13 rotors, 4.2±1.5 cycles). The maximum ShEn bipole was consistently co-located with the pivot zone. ShEn was negatively associated with distance from the pivot zone in simulated spiral waves, rats and sheep. ShEn was modestly inversely associated with CFE; however, there was no relationship at the sites of highest ShEn.
Conclusions—ShEn is a mechanistically-based tool that may assist AF rotor mapping.
- Received August 3, 2012.
- Accepted November 26, 2012.
- Copyright © 2012, American Heart Association, Inc. All rights reserved. Unauthorized use prohibited