Abstract 1510: Heterogeneity of Cell to Cell Communication in the Human Atrio-Ventricular Junction
The atrio-ventricular (AV) junction serves as the only electrical connection between the atria and the ventricles, playing a critical role in slowing the rate of propagation of electrical signals from the sino-atrial (SA) node to the ventricles. The AV junction has a profoundly heterogeneous structure and pattern of protein expression. The expression patterns of connexins in the AV junction are unique and contribute to dual pathway electrophysiology in animal models. However, little is known about connexin distribution in the human AV junction and its relation to AV nodal reentrant tachycardia (AVNRT).
Methods: We used Masson trichrome histology to reconstruct the 3D structure of the human AV junction (n=2), including the inferior nodal extension (INE), compact AV node (AVN), and the lower nodal and His bundles (HB). Immunohistochemistry was used to determine the density of Connexin 43 (Cx43), myocytes, and fibroblasts.
Results: We found that connexins are distributed in a heterogeneous pattern in the human AV junction. The His bundle has a uniformly high density of Cx43. The AVN has an 8.3 ± 3.3 times higher Cx43 expression in the lower nodal bundle as compared to the compact AVN. The inferior nodal extension has two branches. The rightward branch expresses Cx43 at a level similar to the atrium. The leftward branch extends farther than the rightward branch and has a density of Cx43 4.9 ± 2.4 times less than the rightward branch.
Conclusions: The heterogeneous expression of Cx43 in the AV junction may contribute to the dual pathway electrophysiology and AVNRT by providing a molecular and structural basis for the slow and fast pathways.