title: Searching for "order" in atrial fibrillation using electrogram morphology recurrence plots.
abstract: BACKGROUND
  Bipolar electrograms recorded during atrial fibrillation (AF) can have an appearance of chaotic/random behavior. The aim of this study was to use a novel electrogram morphology recurrence (EMR) analysis to quantify the level of order in the morphology patterns in AF.
  
  
  METHODS
  Rapid atrial pacing was performed in seven dogs at 600bpm for 3 weeks leading to sustained AF. Open chest high density electrical recordings were made in multiple atrial sites. EMR plots of bipolar electrograms at each site were created by cross-correlating morphologies of each detected activations with morphologies of every other activation. The following features of the EMR plots were quantified: recurrence rate (RR), determinism (DET), laminarity (LAM), average diagonal line length (L), trapping time (TT), divergence (DIV), and Shannon׳s entropy (ENTR). For each recording site, these measures were calculated for the normal sequence of morphologies and also after random shuffling of the electrogram orders.
  
  
  RESULTS
  Electrograms recordings from a total of 3961 sites had average cycle lengths of 104±22ms resulting in an average of 100±19 activations detected per 10-s recording and an average RR of 0.38±0.28 (range 0.02-1.00). Shuffling the order of the activation morphologies resulted in significant decreases in DET, LAM, L, TT, and ENTR and significant increases in DIV.
  
  
  CONCLUSIONS
  EMR plots of AF electrograms show varying rates of recurrence with patterns that suggest an underlying deterministic structure to the activation sequences. A better understanding of AF dynamics could lead to improved methods in mapping and treating AF.
authors.affiliation: Feinberg Cardiovascular Research Institute, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA. Electronic address: d-gordon@northwestern.edu.
authors.forename: David
authors.initials: D
authors.lastname: Gordon
authors.affiliation: Feinberg Cardiovascular Research Institute, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA. Electronic address: j-goldberger@northwestern.edu.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Goldberger
authors.affiliation: Feinberg Cardiovascular Research Institute, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA. Electronic address: r-arora@northwestern.edu.
authors.forename: Rishi
authors.initials: R
authors.lastname: Arora
authors.affiliation: Feinberg Cardiovascular Research Institute, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA. Electronic address: glais@northwestern.edu.
authors.forename: Gary L
authors.initials: GL
authors.lastname: Aistrup
authors.affiliation: Feinberg Cardiovascular Research Institute, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA. Electronic address: jsnng@northwestern.edu.
authors.forename: Jason
authors.initials: J
authors.lastname: Ng
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology*; D004285:Dogs; D004562:Electrocardiography; D006801:Humans; D009200:Myocardial Contraction
keywords: Atrial fibrillation; Dynamics; Electrograms; Mapping; Non-linear analysis