The morphometric characteristics of the left atrial appendage in heart of adult human

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.