Unique Histological Features of the Left Atrial Posterior Wall

Abstract

The left atrial posterior wall (LAPW) plays a critical role in atrial fibrillation, but the underlying mechanism remains unclear. In the present study, we sought to characterize the histological features of the LAPW. Different atrial regions were dissected from hearts of normal Sprague-Dawley rats and humans. Haematoxylin/eosin and van Gieson staining were used to analyse atrial cardiomyocyte arrangement and collagen distribution, respectively. Intercellular junctions were evaluated by transmission electron microscopy. In contrast with other atrial regions, the LAPW exhibited more disorganized cardiomyocytes, larger intercellular spaces and variable myocardial fibre arrangement. The proportion of collagen was significantly higher in the LAPW than in other atrial regions. Interestingly, desmosomes were sparse along with intercellular gaps in the LAPW. In summary, distinct disarrangement of cardiomyocytes and an abundance of collagen exist in the LAPW. The sparsity of desmosomes in the LAPW may be related to the heterogeneous distribution and separation of atrial myocytes.