title: Mechanisms of wave fractionation at boundaries of high-frequency excitation in the posterior left atrium of the isolated sheep heart during atrial fibrillation.
abstract: BACKGROUND
  High-frequency fractionated electrograms recorded during atrial fibrillation (AF) in the posterior left atrium (PLA) and elsewhere are being used as target sites for catheter ablation. We tested the hypothesis that highly periodic electric waves emerging from AF sources at or near the PLA give rise to the most fractionated activity in adjacent locations.
  
  
  RESULTS
  Sustained AF was induced in 8 isolated sheep hearts (0.5 micromol/L acetylcholine). Endocardial videoimaging (DI-4-ANEPPS) and electric mapping of the PLA enabled spatial characterization of dominant frequencies (DFs) and a regularity index (ratio of DF to total power). Regularity index showed that fractionation was lowest within the area with the maximal DF (DFmax domain; 0.19+/-0.02) and highest within a band of &3 mm (0.16+/-0.02; P=0.047) at boundaries with lower-frequency domains. The numbers of spatiotemporal periodic episodes (25.9+/-2.3) and rotors per experiment (1.9+/-0.7) were also highest within the DFmax domain. Most commonly, breakthrough waves at the PLA traveled toward the rest of the atria (76.8+/-8.1% outward versus 23.2+/-8.1% inward; P<0.01). In both experiments and simulations with an atrial ionic model, fractionation at DFmax boundaries was associated with increased beat-to-beat variability of conduction velocity and directionality with wavebreak formation.
  
  
  CONCLUSIONS
  During stable AF, the PLA harbors regular, fast, and highly organized activity; the outer limit of the DFmax domain is the area where the most propagation pattern variability and fractionated activity occur. These new concepts introduce a new perspective in the clinical use of high-frequency fractionated electrograms to localize sources of AF precisely at the PLA and elsewhere.
authors.affiliation: Institute for Cardiovascular Research, Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, USA.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Kalifa
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Tanaka
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Zaitsev
authors.forename: Mark
authors.initials: M
authors.lastname: Warren
authors.forename: Ravi
authors.initials: R
authors.lastname: Vaidyanathan
authors.forename: David
authors.initials: D
authors.lastname: Auerbach
authors.forename: Sandeep
authors.initials: S
authors.lastname: Pandit
authors.forename: Karen L
authors.initials: KL
authors.lastname: Vikstrom
authors.forename: Robert
authors.initials: R
authors.lastname: Ploutz-Snyder
authors.forename: Arkadzi
authors.initials: A
authors.lastname: Talkachou
authors.forename: Felipe
authors.initials: F
authors.lastname: Atienza
authors.forename: Gérard
authors.initials: G
authors.lastname: Guiraudon
authors.forename: José
authors.initials: J
authors.lastname: Jalife
authors.forename: Omer
authors.initials: O
authors.lastname: Berenfeld
mesh_terms: D000818:Animals; D001281:Atrial Fibrillation / Q000503:physiopathology*; D018780:Body Surface Potential Mapping; D017115:Catheter Ablation; D004562:Electrocardiography / Q000379:methods*; D005583:Fourier Analysis; D006325:Heart Atria / Q000503:physiopathology*; D006329:Heart Conduction System / Q000503:physiopathology; D066298:In Vitro Techniques; D012756:Sheep