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Introduction: The right atrial appendage (RAA) vestibule is an area located in the right atrium between the RAA orifice and the right atrioventricular valve annulus and may be a target for invasive transcatheter procedures. Methods and Results: We examined 200 autopsied human hearts. Three isthmuses (an inferior, a middle, and a superior isthmus) were detected. The average length of the vestibule was 67.4 ± 10.1 mm. Crevices and diverticula were observed within the vestibule in 15.3% of specimens. The isthmuses had varying heights: superior: 14.0 ± 3.4 mm, middle: 11.2 ± 3.1 mm, and inferior: 10.1 ± 2.7 mm (p <.001). The superior isthmus had the thickest atrial wall (at midlevel: 16.7 ± 5.6 mm), the middle isthmus had the second thickest wall (13.5 ± 4.2 mm), and the inferior isthmus had the thinnest wall (9.3 ± 3.0 mm; p <.001). This same pattern was observed when analyzing the thickness of the adipose layer (superior isthmus had a thickness of 15.4 ± 5.6 mm, middle: 11.7 ± 4.1 mm and inferior: 7.1 ± 3.1 mm; p <.001). The average myocardial thickness did not vary between isthmuses (superior isthmus: 1.3 ± 0.5 mm, middle isthmus: 1.8 ± 0.8 mm, inferior isthmus: 1.6 ± 0.5 mm; p >.05). Within each isthmus, there were variations in the thickness of the entire atrial wall and of the adipose layer. These were thickest near the valve annulus and thinnest near the RAA orifice (p <.001). The thickness of the myocardial layer followed an inverse trend (p <.001). Conclusions: This study was the first to describe the detailed topographical anatomy of the RAA vestibule and that of its adjoining isthmuses. The substantial variability in the structure and dimensions of the RAA isthmuses may play a role in planning interventions within this anatomic region. [ABSTRACT FROM AUTHOR]

Background: The pulmonary veins are covered by a myocardial layer, which is often an electrical substrate for atrial fibrillation. The aim of this study was to study the morphologic characteristics of the myocardial sleeves of pulmonary veins by examining a large group of freshly autopsied human material. Methods and Results: The study macroscopically examined a total of 498 pulmonary veins draining the left atrium (120 unpreserved human hearts). In 75.0% of specimens, a classical pulmonary venous pattern was observed. The remainder of specimens either had an additional middle right pulmonary vein (20.0% of cases) or a common left pulmonary vein (5.0% of cases). Among all the veins seen in the classical pulmonary venous drainage type, the left superior pulmonary vein had the longest myocardial sleeves (9.4 ± 4.6 mm; coverage = 60.1 ± 19.4%), followed by the left inferior pulmonary vein (6.6 ± 3.5 mm; coverage = 47.6 ± 18.3%), the right superior pulmonary vein (6.0 ± 2.7 mm; coverage = 50.5 ± 13.9%) and then the right inferior pulmonary vein (5.0 ± 2.8 mm; coverage = 45.6 ± 16.2%; analysis of variance p <.001). In hearts with an additional right pulmonary vein, this vessel had the shortest myocardial sleeves (2.7 ± 1.1 mm; coverage = 36.0 ± 11.6%). In hearts with a common left pulmonary vein, the myocardial sleeves had the longest course for the common vein (13.7 ± 4.4 mm; coverage = 79.7 ± 4.9%). Conclusions: Myocardial sleeves of the pulmonary veins were seen in each examined specimen, however, their length varied significantly. In hearts with a classical venous drainage pattern, the left superior pulmonary vein had the longest sleeves. When present, an additional middle right pulmonary vein had the shortest myocardial sleeves, while the left common pulmonary vein had the longest sleeves. [ABSTRACT FROM AUTHOR]

Background: The left atrial ridge is a structure located in the left atrium between the left‐sided pulmonary veins ostia and the orifice of the left atrial appendage. Since it was commonly misdiagnosed as a thrombus, the ridge is also known as the "coumadin" or "warfarin" ridge. The left atrial ridge is a potential source of arrhythmias and can be an obstacle in ablation procedures. This study aimed to provide information about the occurrence and spatial morphometric characteristics of the left atrial ridge. Methods and Results: The macroscopic morphology of the left atrial ridge was assessed in 200 autopsied human hearts. The ridge was observed in 59.5% of specimens and was absent in the remaining 40.5% of cases. The mean length of the ridge was 22.4 ± 5.1 mm. It was wider at its inferior sector when compared to its superior sector (9.1 ± 5.0 vs 7.9 ± 3.2 mm; P =.028). The total wall thickness measured at the cross section of the ridge was significantly larger in the inferior than in superior sector (6.2 ± 3.5 vs 4.3 ± 1.8 mm; P <.001), although the myocardial thickness was significantly larger at the superior sector (3.1 ± 1.4 vs 1.9 ± 0.9 mm in inferior sector, P <.001). Conclusion: The left atrial ridge is a variable structure, present in 59.5% of humans. The ridge is significantly wider and thicker at its inferior sector, although the actual myocardial layer present within the ridge is thinner at this location. Knowledge about the left atrial ridge morphology is key in avoiding unnecessary interventions or complications during invasive procedures. [ABSTRACT FROM AUTHOR]