A region-specific quantitative profile of autonomic innervation of the canine left atrium and pulmonary veins

The aim of the present study was to determine and quantify the cardiac autonomic innervation of the canine atria and pulmonary vein. Tissue specimens were taken from the canine pulmonary veins (PVs), posterior left atrium (PLA), left atrial roof (LAR), anterior left atrium (ALA), interatrial septum (IAS), and left atrial appendage (LAA) respectively for immunohistochemical analysis and nerve density determination. Both sympathetic and parasympathetic nerve densities decreased in the order: PLA > PV > IAS > LAR > ALA > LAA. For sympathetic nerve, multiple comparisons between any two regions showed a significant difference (P < 0.05-P < 0.01) except for PV vs. PLA, IAS vs. LAR, and LAR vs. ALA; for parasympathetic nerve, all the differences between any pair of regions were statistically significant (P < 0.05-P < 0.01) with the exception of PV vs. PLA, IAS vs. LAR, LAR vs. ALA, and ALA vs. LAA. For both nerve types, there was a decreasing gradient of nerve densities from the external to internal layer (P < 0.001, for each comparisons). Nerve density at the ostia for either nerve type was significantly higher than at the distal segments of PVs (P < 0.001). In summary, the LA and PVs are innervated by sympathetic and parasympathetic nerves in a regionally heterogeneous way, which may be important for the pathophysiological investigation and ablation therapy of atrial fibrillation (AF).