Microanatomy of the myocardial extensions of the pulmonary valve in light of modern catheter ablation methodology.

INTRODUCTION: The muscular sleeves (or myocardial extensions) derived from the right ventricle infundibulum myocardium are considered the true anatomic substrate for right ventricular outflow tract arrhythmias. METHODS: Pulmonary valve specimens obtained from 65 donors (24.6% females, mean age 45.9 ± 15.8 years) were investigated micro-anatomically. Specimens were histologically processed, stained with Masson's Trichrome, and examined under a light microscope. RESULTS: The myocardial extensions were present in the left anterior pulmonary valve sinus in 86.2% of cases, in the right anterior sinus in 89.2% of cases and in 90.7% of cases in the posterior sinus (p = .699). In 69.2% of examined hearts, the myocardial extensions were present in all sinuses. The mean height of the extensions was 4.12 ± 1.76 (left anterior) versus 3.69 ± 1.47 (right anterior) versus 4.28 ± 1.73 mm (posterior) (p = .137). The myocardial extensions occupied an average of 28.9 ± 10.4% of the left anterior sinus, 26.7 ± 11.2% of the right anterior sinus, and 31.9 ± 11.3% of the posterior sinus (p = .044). Sleeves extending beyond the fibro-arterial transition zone were present in at least one sinus in 33.8% of hearts (in 7.7% (5/65) of the left and right anterior sinuses and 21.5% (14/65) of posterior sinus, p = .021). CONCLUSIONS: The myocardial extensions of the pulmonary valve are common anatomical entities. Although the length of the myocardial sleeves is similar in all pulmonary valve sinuses, their relative extent is greatest in the posterior sinus. Long sleeves that spread beyond the fibro-arterial transition zone were observed in one-third of hearts, predominantly in the posterior sinus. Myocardial and fibrous tissue layer thicknesses varied considerably.

Morphometric characteristics of myocardial sleeves of the pulmonary veins.

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.

Anatomy of the left atrial ridge (coumadin ridge) and possible clinical implications for cardiovascular imaging and invasive procedures.

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.

Topographical anatomy of the right atrial appendage vestibule and its isthmuses.

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.

Correct human cardiac nomenclature.

Proper heart's nomenclature is very important in daily clinical practice and research studies, and when it is consistent, it can facilitate better communication between different medical specialists. The general rule of the anatomy is to describe organs and their structures in attitudinally correct position. However, the use of the old-fashioned Valentine position (where the heart is described as if it were standing on its apex) is still in use to describe important cardiac structures. Upon closer analysis, all main chambers of the heart and their associated subcomponents have mislabeled structures that should be renamed. In this article we aimed to emphasize the limitations of Valentinian nomenclature, present proper anatomical names of the most important heart's structures and advocate to change certain mislabeled anatomical structures. Attitudinally correct designations presented in this study will benefit all medical specialties, and they will reinforce the importance of consistent orientational naming. Correct naming of heart's structures will also help improve communication between different medical specialists.

Morphology of the Vieussens valve and its imaging in cardiac multislice computed tomography.

INTRODUCTION: To deliver accurate morphological descriptions of the Vieussens valve (VV) and to investigate whether this structure could be visualized using standard contrast-enhanced electrocardiogram-gated multislice computed tomography (MSCT). METHODS: A total of 145 human autopsied hearts and 114 cardiac MSCT scans were examined. RESULTS: The VV was observed in both study groups, however, the detection rate was significantly worse in the MSCT examination (18.4% in MSCT vs 62.1% in cadavers, P < .0001). The VV height was larger in MSCT patients (2.8 ± 1.2 vs 5.4 ± 1.7 mm; P < .0001). No significant difference was found in the measured distance between the VV and the coronary sinus ostium between the two separate subgroups (27.3 ± 9.5 vs 24.4 ± 5.8 mm; P = .18). In autopsied material the most frequent valve location was the anterior wall of the coronary sinus (43.3%); the same was observed in MSCT scans (71.4%). CONCLUSION: The VV is a common heart structure, present in over 60% of humans, located mainly on the anterior and superior circuit of the coronary sinus, with relatively high morphological variability. Large VVs, which pose a significant obstacle in catheterization procedures, may be visualized using standard-protocol contrast-enhanced cardiac MSCT.

Topographic characteristics of the left atrial medial isthmus.

BACKGROUND: The purpose of this study was to provide detailed topography of the left atrial medial isthmus (situated between the right inferior pulmonary vein ostium and the medial part of the mitral annulus). METHODS: Two hundred human hearts (Caucasian, 22.5% females, 48.7 ± 4.9 years old) were investigated. RESULTS: The mean length of the medial isthmus was 42.4 ± 8.6 mm. Additionally, the medial isthmus line was divided by the oval fossa into three sections with equal mean lengths (upper: 14.2 ± 7.2 vs middle: 14.1 ± 6.1 vs lower: 14.9 ± 4.6 mm; P > .05). The left upper section of the atrial wall was thinner than the lower section (2.5 ± 1.1 vs 3.4 ± 1.6 mm; P < .0001). This study noted three separate spatial arrangements of the isthmus line. Type I (54.5%) had an oval fossa located outside the isthmus line; type II (32.5%) had an oval fossa crossed by the isthmus line, and type III (13.0%) had an oval fossa rim located tangentially to the isthmus line. In 68.5% of the examined specimens, the isthmus area had a smooth surface. Conversely, the remaining 31.5% had additional structures within its borders such as diverticula, recesses, and tissue bridges. CONCLUSION: This study is the first to describe the morphometric and topographical features of the left atrial medial isthmus. Interventions within the medial isthmus line should be performed cautiously, especially when they are transected by the oval fossa (32.5%). Careful navigation of the area is also recommended due to the possibility of existent additional structures. The latter could lead to catheter entrapment during ablation procedures.

Fixative properties of honey solutions as a formaldehyde substitute in cardiac tissue preservation.

OBJECTIVES: To evaluate the properties of natural sweetener solutions in whole organ preservation and assess their influence on the dimension, weight and shape of cardiac tissue samples in stated time intervals, up to a one-year period of observation. BACKGROUND: Tissue fixation is essential for biological sample examination. Many negative toxic effects of formaldehyde-based fixatives have forced us to seek alternatives for formaldehyde based solutions. It has been demonstrated that natural sweeteners can preserve small tissue samples well and that these solutions can be used in histopathological processes. However, their ability to preserve whole human organs are unknown. METHODS: A total of 30 swine hearts were investigated. Three study groups (n = 10 in each case) were formed and classified on the type of fixative: (1) 10% formaldehyde phosphate-buffered solution (FPBS), (2) 10% alcohol-based honey solution (ABHS), (3) 10% water-based honey solution (WBHS). Samples were measured before fixation and in the following time points: 24 hours, 72 hours, 168 hours, 3 months, 6 months and 12 months. RESULTS: The WBHS failed to preserve heart samples and decomposition of tissues was observed one week after fixation. In half of the studied parameters, the ABHS had similar modifying tendencies as compared to FPBS. e overall condition of preserved tissue, weight, left ventricular wall thickness, right ventricular wall thickness and the diameter of the papillary muscle differed considerably. CONCLUSIONS: The ABHS may be used as an alternative fixative for macroscopic studies of cardiac tissue, whereas the WBHS is not suited for tissue preservation.

Mutual Arrangements of Coronary Blood Vessels within the Right Atrial Appendage Vestibule.

BACKGROUND: The aim of our study was to investigate the presence and mutual relationships of coronary vessels within the right atrial appendage (RAA) vestibule. METHODS: We examined 200 autopsied hearts. The RAA vestibule was cross-sectioned along its isthmuses (superior, middle, and inferior). RESULTS: The right coronary artery (RCA) was present in 100% of the superior RAA isthmuses but absent in 2.0% of hearts within the middle isthmus and in 6.5% of hearts within the inferior RAA isthmus. Its diameter was quite uniform along the superior (2.6 ± 0.8 mm), middle (2.9 ± 1.1 mm), and inferior (2.7 ± 0.9 mm) isthmuses (p = 0.12). The location of the RCA varied significantly, and it was sometimes accompanied by other accessory coronary vessels. In all the isthmuses, the RCA ran significantly closer to the endocardial surface than to the epicardial surface (p < 0.001). At the superior RAA isthmus, the artery was furthest from the right atrial endocardial surface and this distance gradually decreased between the middle RAA isthmus and the inferior RAA. CONCLUSIONS: This study was the most complex analysis of the mutual arrangements and morphometric characteristics of coronary blood vessels within the RAA vestibule. Awareness of additional blood vessels within the vestibule can help clinicians plan and perform safe and efficacious procedures in this region.

Morphology and Position of the Right Atrioventricular Valve in Relation to Right Atrial Structures.

The right atrioventricular valve (RAV) is an important anatomical structure that prevents blood backflow from the right ventricle to the right atrium. The complex anatomy of the RAV has lowered the success rate of surgical and transcatheter procedures performed within the area. The aim of this study was to describe the morphology of the RAV and determine its spatial position in relation to selected structures of the right atrium. We examined 200 randomly selected human adult hearts. All leaflets and commissures were identified and measured. The position of the RAV was defined. Notably, 3-leaflet configurations were present in 67.0% of cases, whereas 4-leaflet configurations were present in 33.0%. Septal and mural leaflets were both significantly shorter and higher in 4-leaflet than in 3-leaflet RAVs. Significant domination of the muro-septal commissure in 3-leflet valves was noted. The supero-septal commissure was the most stable point within RAV circumference. In 3-leaflet valves, the muro-septal commissure was placed within the cavo-tricuspid isthmus area in 52.2% of cases, followed by the right atrial appendage vestibule region (20.9%). In 4-leaflet RAVs, the infero-septal commissure was located predominantly in the cavo-tricuspid isthmus area and infero-mural commissure was always located within the right atrial appendage vestibule region. The RAV is a highly variable structure. The supero-septal part of the RAV is the least variable component, whereas the infero-mural is the most variable. The number of detected RAV leaflets significantly influences the relative position of individual valve components in relation to right atrial structures.

Topography of the oblique vein of the left atrium (vein of Marshall).

BACKGROUND: The oblique vein of the left atrium is of interest for electrophysiologists working in the field of both basic science and clinical practice. AIMS: We aimed to examine the topographic anatomy of the oblique vein and to assess the vein's location and relationships with surrounding cardiac structures. METHODS: A total of 200 autopsied adult human hearts were examined. RESULTS: The oblique vein was observed in 71% of the hearts. Its mean (SD) total length was 30.8 (13.6) mm. In hearts with the oblique vein, a larger distance was observed between the left inferior pulmonary vein (LIPV) and great cardiac vein (mean [SD], 18.6 [5.1] mm vs 16.3 [4.8] mm; P = 0.004), between the left atrial appendage (LAA) and LIPV (mean [SD], 17.8 [6.8] mm vs 15.1 [5.2] mm; P = 0.007), and between the LAA and left superior pulmonary vein (LSPV; mean [SD], 28.5 [7.2] mm vs 21.3 [6.4] mm; P <0.001). Hearts with a classic pattern of left­sided pulmonary veins were categorized into 4 types based on the length of oblique vein extension. In type I, the vein extended below the level of the LIPV (21.9%); in type II, to the level of the LIPV (47.7%); in type III, to the level of the interpulmonary area (17.2%); and in type IV, to the level of the LSPV (13.3%). In each type, the distance between the oblique vein and LIPV was shorter than that between the oblique vein and LAA Conclusions: The oblique vein had a variable course and differing lengths of extension. The presence of the oblique vein was connected with a greater distance between the left­sided pulmonary veins and LAA.

Alarming decline in recognition of anatomical structures amongst medical students and physicians.

BACKGROUND: Insufficient anatomical training can put patients' safety at risk. The aim of this study was to assess the proficiency of medical students and physicians in identifying labeled anatomical structures. The second aim of the study was to evaluate factors that can affect this recognition. METHODS: An internet-based survey where participants had to correctly identify labeled anatomical structures on cadaveric specimens was designed. RESULTS: The study group included 1186 participants (58.7% females): 931 medical students and 255 medical graduates from all twelve Polish medical schools. The mean total survey score for the entire study group was 65.6%. Students gained significantly higher results than graduates (total: 67.3% vs. 59.5%, P<0.001); 331 (27.9%) participants did not pass the test (<60). There was a correlation observed between points gained in this survey and grade obtained in the gross anatomy course (P<0.001). Multivariable logistic regression found that participation in cadaver laboratory classes most strongly increases anatomical competencies (OR=5.30, 95%CI=1.20-23.40, P=0.03). Other significant factors boosting anatomical proficiency were membership in students' scientific clubs, being male, and having a high grade (≥80%) in initial gross anatomy course. The time since anatomy course completion was negatively correlated with the total survey score (OR=0.86, 95%CI=0.81-0.92, P<0.001). CONCLUSIONS: Anatomical knowledge of Polish medical students is moderate (<70%) and it significantly decreases with time. Anatomical structure recognition can be up to 25% lower in highly trained physicians when compared to pre-clinical medical students. This trend may be reversed by replacing subject-based anatomy courses with system-based (integrated) curricula at the undergraduate level or introducing short refresher anatomical courses during postgraduate training.