title: Bipolar electrogram shannon entropy at sites of rotational activation: implications for ablation of atrial fibrillation.
abstract: 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 because of directional information encoded in these signals. We aimed to determine whether Shannon entropy (ShEn), a measure of signal amplitude distribution, could differentiate the pivot from surrounding peripheral regions and thereby assist clinical rotor mapping.
  
  
  RESULTS
  Bipolar electrogram recordings were studied in 4 systems: (1) computer simulations of rotors in a 2-dimensional atrial sheet; (2) isolated rat atria recorded with a multi-electrode array (n=12); (3) epicardial plaque recordings of induced AF in hypertensive sheep (n=11); and (4) 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 complex fractionated electrogram 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 colocated 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 complex fractionated electrogram; however, there was no relationship at the sites of highest ShEn.
  
  
  CONCLUSIONS
  ShEn is a mechanistically based tool that may assist AF rotor mapping.
authors.affiliation: Centre for Heart Rhythm Disorders, University of Adelaide and Royal Adelaide Hospital, Adelaide, Australia.
authors.forename: Anand N
authors.initials: AN
authors.lastname: Ganesan
authors.forename: Pawel
authors.initials: P
authors.lastname: Kuklik
authors.forename: Dennis H
authors.initials: DH
authors.lastname: Lau
authors.forename: Anthony G
authors.initials: AG
authors.lastname: Brooks
authors.forename: Mathias
authors.initials: M
authors.lastname: Baumert
authors.forename: Wei Wen
authors.initials: WW
authors.lastname: Lim
authors.forename: Shivshankar
authors.initials: S
authors.lastname: Thanigaimani
authors.forename: Sachin
authors.initials: S
authors.lastname: Nayyar
authors.forename: Rajiv
authors.initials: R
authors.lastname: Mahajan
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Kalman
authors.forename: Kurt C
authors.initials: KC
authors.lastname: Roberts-Thomson
authors.forename: Prashanthan
authors.initials: P
authors.lastname: Sanders
mesh_terms: D000200:Action Potentials; D000328:Adult; D000368:Aged; D000818:Animals; D001281:Atrial Fibrillation / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D017115:Catheter Ablation; D003198:Computer Simulation; D004195:Disease Models, Animal; D022062:Electrophysiologic Techniques, Cardiac; D019277:Entropy; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D018579:Patient Selection; D011237:Predictive Value of Tests; D051381:Rats; D017207:Rats, Sprague-Dawley; D012756:Sheep; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors; D056969:Voltage-Sensitive Dye Imaging