Aim. To determine the left atrial dimensions, their ratios and relationships that characterize anatomy for left atrium structure in the normal human adult using the model of the atrial end-diastolic phase. Methods. We studied 54 heart specimens of subjects aged 3588 years who died from non-cardiac causes. The atrial end-diastolic phase was modeled by filling a specimen fixed in 1% formalin with liquid silicone. After silicone hardened, we performed morphometric measurements by a caliper. The data were processed by using a cluster, correlation and variance analysis. For pairwise comparison, we used the MannWhitney U-test or a two-sided t-test. Results. The article presents mean, standard deviation, median, 25th percentile and 75th percentile and coefficients of variation for the length, width and sagittal size of the left atrium, as well as the values of the distances between the pulmonary vein orifices, which characterize the dimensions of the left atrium posterior wall. Based on the left atrial size differences and their ratios, the specimens were divided into three clusters. The first (n1=23) and second clusters (n2=10) were represented by hearts with a cubic atrium; the second group differed from the first in the larger size of the left atrium. The third cluster (n3=21) included the hearts in which the largest left atrium size was the width, so the shape of the atria resembled a parallelepiped. The typical number of the pulmonary vein ostia we found in 91% of the specimens. The posterior wall of the left atrium, with a common number and topography of the ostia, were rectangle or an unequal trapezium in shape. We analyzed correlations between the sizes of the heart, left atrium and its posterior wall. We concretized the conceptual apparatus concerning the nomenclature and terminology of the left atrium anatomical structures. Conclusion. Based on the size ratio, two shape variations of the left atrium body can be identified: cubic or parallelepiped; cubic atria can be divided into large and small; the co-directional dimensions of the left atrial body and its posterior wall showed the strongest correlations.

INTRODUCTION: The syntopy of the left atrial (LA) structures is the least studied aspect of the normal heart anatomy. The morphometric data on the position of orifices of the pulmonary veins in the LA walls relative to the adjacent heart structures and heart vessels are important as reference parameters of heart morphology and are needed in the endovascular treatment of atrial fibrillations. AIM: To establish the general patterns and topospecific peculiarities of the location of the pulmonary vein orifices relative to the oval fossa and orifices of the venae cavae using morphometric methods of anatomical preparations of conventionally normal adult human heart. MATERIALS AND METHODS: Fiftyfour wet anatomical preparations of the heart without macroscopic signs of hemodynamically significant cardiac pathology were studied. The preparations were obtained from patients aged 3589 years who died from diseases not related to heart pathology. LA diastole was modeled by filling its cavity with silicone; after it hardened, the distances from the oval fossa and orifices of the venae cavae to the orifices of the pulmonary veins were measured using sliding calipers. RESULTS: The article presents variation, medians, and extreme values of distances from the oval fossa and orifices of the venae cavae to the orifices of the pulmonary veins at the site of their opening to LA. The significance of differences of morphometric parameters of the topography was evaluated, and their correlation and oneway regression analyses were implemented. The strongest regression dependence was found for LA width and distance from the orifice of the superior vena cava to the orifice of the left inferior pulmonary vein (Y) r2 = 0.45; Х = 19.94 + 0.545Y). The heart dimensions and LA length were not significant predictors for the studied parameters. CONCLUSION: The right pulmonary veins were located expectedly closer to the orifices of the venae cavae and the oval fossa than the left pulmonary veins. The narrowest was the space between the orifices of the superior vena cava and the right superior pulmonary vein. The farthest from the orifices of both venae cavae was the orifice of the left inferior pulmonary artery. The strongest correlation relationships were characteristic of the distances from the orifices of both venae cavae to the orifices of the homolateral pulmonary veins, which we propose to consider as one of the criteria of the harmoniousness of the structure of the atrial complex.