Role of the Left Atrial Anatomy in the Maintenance of Three-Dimensional Scroll Waves in Acute, Stretch-Related and Cholinergic Atrial Fibrillation

Abstract

The mechanisms that maintain atrial fibrillation (AF) are incompletely understood. We hypothesized that 3-D scroll waves (SWs) confined to specific left atrial (LA) anatomical structure are involved in the maintenance of stretch-related (SRAF) and cholinergic AF with stretch (ChAF). Methods: In 13 isolated sheep hearts, optical membrane potential images were recorded, by using two CCD cameras and a cardio-endoscope, simultaneously from the epicardial and endocardial surfaces of the posterior LA (PLA, n=8) or the LA appendage (LAA, n=5). SRAF was induced by burst pacing under increased LA pressure (12 cm H₂O), and ChAF did so additional perfusion of 0.1 µM acetylcholine. Results: During SRAF, major activation pattern in LAA was either breakthrough (44%) or one-way propagation (30%), whereas that in PLA was SWs (30%), which were anchored at LA-PV junction. During ChAF, major activation pattern in LAA was SWs (53%), which were anchored at the periphery of pectinate muscles. Numerical simulations suggest that the thinnest region of LA will favor the anchoring of SWs via shortening of atrial wave length resulting from an increase of stretch-activated ion channel conductance. Conclusion: Transmural SWs play an important role to maintain AF induced by mechanical stretch and cholinergic stimulation. The thinnest LA region will provide a structural substrate in favor of perpetuation of these SWs.