title: Organizational index mapping to identify focal sources during persistent atrial fibrillation.
abstract: BACKGROUND
  Localized rotors have been implicated in the mechanism of persistent atrial fibrillation (AF). Although regions of highest dominant frequency (DF) on spectral analysis of the left atrium (LA) have been said to identify rotors, other mechanisms such as wavefront collisions will sporadically also generate an inconsistent distribution of high DF. We hypothesized that if drivers of AF were present, their distinctive spectral characteristics would result more from their temporal stability than their high frequency.
  
  
  RESULTS
  Ten patients with persistent AF underwent LA noncontact mapping. Following subtraction of far-field ventricular components, noncontact electrograms at 256 sites underwent fast Fourier transform. Mean absolute difference in DF between 5 sequential 7-second segments of AF was defined as the DF variability (DFV) at each site. Mean ratio of the DF and its harmonics to the total power of the spectrum was defined as the organizational index (OI). Mean DFV was significantly lower in organized areas (OI > 1 SD above mean) than at all sites (0.34 ± 0.04 vs 0.46 ± 0.04 Hz; P < 0.001). When organized areas were ablated during wide-area circumferential ablation, AF organized in remote regions (LA appendage ΔOI ablated vs unablated: +0.21 [0.06-0.41] vs -0.04 [-0.14-0.05]; P = 0.005).
  
  
  CONCLUSIONS
  At sites of organized activation, the activation frequency was also significantly more stable over time. This observation is consistent with the existence of focal sources, and inconsistent with a purely random activation pattern. Ablation of such regions is technically feasible, and was associated with organization of AF in remote atrial regions.
authors.affiliation: Imperial College London, UK.
authors.forename: Julian W E
authors.initials: JWE
authors.lastname: Jarman
authors.affiliation: Imperial College London, UK.
authors.forename: Tom
authors.initials: T
authors.lastname: Wong
authors.affiliation: Imperial College London, UK.|St. Mary's Hospital, Imperial College Healthcare NHS Trust, London, UK.
authors.forename: Pipin
authors.initials: P
authors.lastname: Kojodjojo
authors.affiliation: Imperial College London, UK.
authors.forename: Hilmar
authors.initials: H
authors.lastname: Spohr
authors.affiliation: Imperial College London, UK.|St. Mary's Hospital, Imperial College Healthcare NHS Trust, London, UK.
authors.forename: Justin E R
authors.initials: JER
authors.lastname: Davies
authors.affiliation: Imperial College London, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Roughton
authors.affiliation: Imperial College London, UK.|St. Mary's Hospital, Imperial College Healthcare NHS Trust, London, UK.
authors.forename: Darrel P
authors.initials: DP
authors.lastname: Francis
authors.affiliation: Imperial College London, UK.|St. Mary's Hospital, Imperial College Healthcare NHS Trust, London, UK.
authors.forename: Prapa
authors.initials: P
authors.lastname: Kanagaratnam
authors.affiliation: Imperial College London, UK.
authors.forename: Mark D
authors.initials: MD
authors.lastname: O'Neill
authors.affiliation: Imperial College London, UK.
authors.forename: Vias
authors.initials: V
authors.lastname: Markides
authors.affiliation: Imperial College London, UK.|St. Mary's Hospital, Imperial College Healthcare NHS Trust, London, UK.
authors.forename: D Wyn
authors.initials: DW
authors.lastname: Davies
authors.affiliation: Imperial College London, UK.|St. Mary's Hospital, Imperial College Healthcare NHS Trust, London, UK.
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Peters
mesh_terms: D000368:Aged; D020517:Atrial Appendage / Q000503:physiopathology; D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000601:surgery; D016279:Atrial Function, Left; D017115:Catheter Ablation; D004351:Drug Resistance; D005260:Female; D006334:Heart Function Tests / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011667:Pulmonary Veins / Q000503:physiopathology; D015203:Reproducibility of Results
keywords: Fourier analysis; atrial fibrillation; catheter ablation; dominant frequency; rotors; spectral analysis