Abstract 632: Autonomic Innervation in Atrial Fibrillation - Immunohistochemical Findings
Atrial fibrillation (AF) has been determined to be a multifactorial disease of the atria. In addition to electrophysiological and structural remodeling during AF changes in cardiac autonomic innervation have been postulated. Can differences in nervous innervation pattern be documented in patients with and without AF? Preparation of postmortally isolated hearts of patients with sinusrhythm (SR) and with documented long-lasting AF. Histological sectioning of predifened areas and quantification of nerves. Differentiation using immunohistochemistry in predominantly adrenergic (=sympathetic, Tyrosin-Hydroxylase Antibody), predominantly cholinergic (=parasympathetic, Cholin-Acetyltransferase Antibody) and mixed (adrenergic and cholingeric staining) nerves. Comparison in between patients with AF and SR. Preparation of 20 hearts of patients with SR and 11 patients with AF. In all studied segments a mean of 0.33 (±0.19) nerves/mm2 were identified (SR: 0.35±0.21; AF: 0.31±0.22; p=0.39). Nerve density is high in the region of the pulmonary vein ostia (SR: 0.38±0.19; AF: 0.35±0.21). A total of 1887 (AF: 586; SR: 1301) nerves were differentiated using immunohistochemistry. In hearts with AF there is a significantly lower number of predominantly cholinergic nerves (0.004±0.002 versus 0.02±0.01; p=0.04) and a trend towards higher density of predominantly adrenergic nerves (0.042±0.011 versus 0.019±0.005, p=0.05) whereas mixed nerve density is comparable (0.26 ± 0.21 vs. 0.30 ± 0.24, p=0.84). In regard to the location there is a significantly smaller density of predominantly cholinergic nerves in the pulmonary vein region of hearts with AF (0.004±0.02 versus 0.065±0.121, p=0.014) but not in other studied regions. The pulmonary vein ostial regions display rich autonomic innervation. Most nerves display mixed (cholinergic and adrenergic) immunohistochemical staining. No differences in overall autonomic innervation were detected. Hearts with AF though have a significantly lower density of predominantly cholinergic nerves. These differences may play a role in the perpetuation of AF (autonomic remodeling).