Abstract 1233: Atrial Autonomic Remodeling in a Canine Model of Congestive Heart Failure
Introduction: Congestive heart failure (CHF) is a known cause of atrial fibrillation (AF). Changes in autonomic innervation might contribute to the pathophysiologic mechanisms of AF in this condition.
Methods: In five normal adult dogs, CHF was induced by rapid ventricular pacing (4 weeks at 240 bpm). 8 normal dogs not subjected to pacing were employed as controls. After the 4 weeks time period, the pulmonary veins (PV), posterior left atrium (PLA) and left atrial appendage (LAA) were harvested and frozen in liquid nitrogen. Dopamine beta-hydroxylase (DBH) (blue color) were used to stain sympathetic (S) nerves, while choline acetyltransferase (ChAT) (brown color) were used to stain parasympathetic (P) nerves.
Results: The PLA was, among the three regions, the most richly innervated with nerve bundles in both groups; the vast majority of nerve bundles demonstrated co-localization of P and S nerve fibers. Notably, nerve bundles in the PLA were significantly larger in the CHF than in the control group (0.12±0.15 mm2 in the controls vs 0.37±0.17 mm2 in the CHF group, p=0.02). The picture represents a group of bundles in a control dog (panel A) and a single bundle in a CHF dog (panel B) both at 10X magnification. P fibers predominated over S fibers inside the bundles in both groups, but a shift to an increase of sympathetic elements was observed in the CHF group (S/P ratio 0.14 in controls vs 0.34 in CHF, p<0.05).
Conclusions: Congestive heart failure produces an increase in nerve size and a significant change in the relative distribution of P and S fibers in the left atrium. Atrial autonomic remodeling may play a role in the development of atrial fibrillation in congestive heart failure.