Mechanisms of wave fractionation at boundaries of high-frequency excitation in the posterior left atrium of the isolated sheep heart during atrial fibrillation.
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.
Kalifa
Jérôme
J
Institute for Cardiovascular Research, Department of Pharmacology, SUNY Upstate Medical University, Syracuse, NY 13210, USA.
Tanaka
Kazuhiko
K
Zaitsev
Alexey V
AV
Warren
Mark
M
Vaidyanathan
Ravi
R
Auerbach
David
D
Pandit
Sandeep
S
Vikstrom
Karen L
KL
Ploutz-Snyder
Robert
R
Talkachou
Arkadzi
A
Atienza
Felipe
F
Guiraudon
Gérard
G
Jalife
José
J
Berenfeld
Omer
O
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