Chronic AF in goats increased obstructive fibrosis (17.5 vs 8.6 fibers/mm2) and slowed transverse conduction velocity (0.40 vs 0.53 m/s) compared to controls, facilitating reentry.
Does chronic atrial fibrillation alter fibrosis architecture and local conduction to facilitate reentrant activity following premature stimulation in a goat model?
In a goat model, chronic AF induces obstructive fibrosis and slows transverse conduction velocity, creating a substrate that facilitates reentry and AF initiation following premature stimuli.
Absolute Event Rate: 0.4% vs 0.53%
INTRODUCTION: Patients with paroxysmal atrial fibrillation (AF) often transition between sinus rhythm and AF. For AF to initiate there must be both a trigger and a substrate that facilitates reentrant activity. This trigger is often caused by a premature atrial contraction or focal activations within the atrium. We hypothesize that specific architectures of fibrosis alter local conduction to enable AF. METHODS AND RESULTS: Control goats (n = 13) and goats in chronic AF (for an average of 6 months, n = 6) had a high-density electrode plaque placed on the LA appendage. Conduction patterns following a premature atrial contraction, caused by an electrical stimulation, were quantified to determine regions of conduction slowing. These regions were compared to architecture, either diffuse fibrosis or regions of obstructive fibrosis, and overall fibrosis levels as determined by histology from the mapped region. The chronic AF goats had more obstructive fibrosis than the controls (17.5 ± 8.0 fibers/mm(2) vs. 8.6 ± 3.0 fibers/mm(2)). Conduction velocity of the AF goats was significantly slowed compared to the control goats in the transverse direction (0.40 ± 0.04 m/s vs. 0.53 ± 0.15 m/s) but not in the longitudinal direction (0.70 ± 0.27 m/s vs. 0.76 ± 0.18 m/s). CONCLUSIONS: AF-induced atrial remodeling leads to increased obstructive fibrosis and conduction velocity slowing transverse to fiber orientation following premature stimuli. The decrease in conduction velocity causes a decrease in the cardiac wavelength, and increases the likelihood of reentry and AF onset.
Angel et al. (Fri,) conducted a other in Chronic Atrial Fibrillation (n=19). Chronic AF model vs. Control goats was evaluated on Transverse conduction velocity (m/s). Chronic AF in goats increased obstructive fibrosis (17.5 vs 8.6 fibers/mm2) and slowed transverse conduction velocity (0.40 vs 0.53 m/s) compared to controls, facilitating reentry.