The Morphometric Characteristics of the Left Atrial Appendage in Heart of Adult Human

Abstract

The aim of the study was a morphometric characteristic of the left atrial appendage of a conditionally normal adult heart with a different number of lobes of this structure. We studied 52 preparations of the heart weighing 250-400 grams of people aged 36-89 who died from causes not related to diseases of the heart, blood vessels, muscle or connective tissue. The left atrium of the heart was filled with liquid silicone with a hardener. During the silicone hardening, the preparations were suspended so that the its lower wall was raised above the table plane by 10–15º. After the silicone hardened, the overall dimensions of the heart, left atrial appendage, and its lobes were measured with a caliper. The number of lobes and edges of the atrial appendage was determined. Nonparametric tests were used for statistical analysis of differences. It was established that in 71,1% of cases the left atrial appendages had two lobes, in 21,2% three lobes, in 7,7% it was single-lobed. The proximal lobes of the three-lobed left atrial appendages could be short or long. Three-lobed left atrial appendages were longer than two-lobed ones (U=106,5; p=0,018). The values of the width of the left atrial appendage of the heart did not depend on the number of its lobes (H=0,95; p=0,62). In 98,1% of cases, the atrial appendage had an edge directed towards the pulmonary artery, in 96,1% of cases they had an edge facing the diaphragmatic surface of the heart, in 94,2% of the preparations there was an edge facing the apex of the heart, in 25% of cases there was a left atrial edge directed back and up. Most often, in 65,4% of cases, the left appendage of the heart had three edges: pulmonary, apical and diaphragmatic. Thus, it was established that the left atrial appendage of the heart is characterized by a pronounced anatomical variability in shape. A different number of lobes, edges of the left atrial appendage, a different combination of these features and the ratio of the length and width of the lobes of the atrial appendage and the atrial appendage as a whole are proposed to be considered as criteria for distinguishing anatomical types and structural variants of the human left atrial appendage.