Morphometric characteristics and histotopography of the left atrium walls

Abstract

Background. Knowledge of the anatomical features of the left atrium walls will minimize complications during the Cox-Maze surgery.
 Aim. To clarify common features and local anatomical specificities of the anterosuperior, lateral and inferior walls of the left atrial body of the heart of an adult.
 Material and methods. From 60 preparations of the hearts of men and women aged 3589 years who died from non-cardiac causes, 61 histotopograms and 180 anatomical sections of the left atrium walls were made. A stereoscopic microscope (4.715 magnification), a histological microscope (40 magnification), and an image recognition program were used. Nonparametric dispersion, correlation, one-way regression analysis were applied. The significance of differences was assessed by the MannWhitney U-test. The results were presented as medians.
 Results. Anatomical markers of the anterosuperior wall were a compact group of transverse myocardial fibers (anterior interatrial Bachmann bundle) and a thinned section of the lower third of the medial half of the wall. A feature of the lateral wall was a group of oblique myocardial fibers (left lateral ridge). The inferior wall was characterized by well-developed subepicardial tissue. Anteroposterior wall in the medial area (5130 m) and lateral wall (5243 m) were thin. The epicardium with subepicardial tissue in the medial part of the inferior wall was thicker (4750 m) than in the lateral (2651 m) and anterosuperior (2535 m) walls. The myocardium of the anteroposterior wall (2714 m) was thicker than the myocardium of both the lateral (2213 m) and inferior wall in its central (1947 m) and lateral (1913 m) sections. The median thickness of the endocardium of different walls varied from 335 to 426 m. The wall thickness in the upper third mostly depended primarily on the myocardium thickness, and in the inferior third on the epicardium and subepicardial tissue thickness.
 Conclusion. For the walls of the left atrium, their thickening towards the coronary sulcus was common due to the subepicardial adipose tissue. The peculiarities were the differences of the left atrium walls in thickness and their unique pattern of myocardial anatomy.